A guide to cancer immunotherapy: from T cell basic science to ...

Cancer immunotherapy has now revolutionized the field of oncology by prolonging survival of patients with rapidly fatal cancers. The number of ... Skiptomaincontent Thankyouforvisitingnature.com.YouareusingabrowserversionwithlimitedsupportforCSS.Toobtain thebestexperience,werecommendyouuseamoreuptodatebrowser(orturnoffcompatibilitymodein InternetExplorer).Inthemeantime,toensurecontinuedsupport,wearedisplayingthesitewithoutstyles andJavaScript. Advertisement nature naturereviewsimmunology reviewarticles article Aguidetocancerimmunotherapy:fromTcellbasicsciencetoclinicalpractice DownloadPDF DownloadPDF Subjects CancerimmunotherapyDrugdiscoveryImmunology AbstractTheTlymphocyte,especiallyitscapacityforantigen-directedcytotoxicity,hasbecomeacentralfocusforengagingtheimmunesysteminthefightagainstcancer.BasicsciencediscoverieselucidatingthemolecularandcellularbiologyoftheTcellhaveledtonewstrategiesinthisfight,includingcheckpointblockade,adoptivecellulartherapyandcancervaccinology.Thisareaofimmunologicalresearchhasbeenhighlyactiveforthepast50yearsandisnowenjoyingunprecedentedbench-to-bedsideclinicalsuccess.Here,weprovideacomprehensivehistoricalandbiologicalperspectiveregardingtheadventandclinicalimplementationofcancerimmunotherapeutics,withanemphasisonthefundamentalimportanceofTlymphocyteregulation.Wehighlightclinicaltrialsthatdemonstratetherapeuticefficacyandtoxicitiesassociatedwitheachclassofdrug.Finally,wesummarizeemergingtherapiesandemphasizetheyettobeelucidatedquestionsandfuturepromisewithinthefieldofcancerimmunotherapy. IntroductionTheideatodeploytheimmunesystemasatooltotreatneoplasticdiseaseoriginatedinthenineteenthcentury1.WilhelmBuschandFriedrichFehleisenwerethefirsttodescribeanepidemiologicalassociationbetweenimmunestatusandcancer.Theynoticedspontaneousregressionoftumoursfollowingthedevelopmentoferysipelas,asuperficialskininfectionmostcommonlycausedbyStreptococcuspyogenes1.Later,WilliamColey,oftencalledthe‘FatherofCancerImmunotherapy’,retrospectivelydemonstratedthaterysipelaswasassociatedwithabetteroutcomeinpatientswithsarcoma2.Withhopesofprospectivelyverifyinghisepidemiologicalevidence,Coleytreatedpatientswithcancerwithextractsofheat-inactivatedS.pyogenesandSerratiamarcescenstoboostimmunity3.Thisextract,termed‘Coley’stoxins’,possessedpotentimmunostimulatorypropertiesandachievedfavourableresponsesinvariouscancers2.However,lackofscientificrigourandreproducibility,inconcertwiththediscoveryofradiotherapyandchemotherapeuticagents,preventedtreatmentwith‘Coley’stoxins’frombecomingstandardpractice1.Theconceptofcancerimmunotherapyresurfacedinthetwentiethcenturyandmadesignificantheadwaywiththeadventofnewtechnology.In1909,PaulEhrlichhypothesizedthatthehumanbodyconstantlygeneratesneoplasticcellsthatareeradicatedbytheimmunesystem3.LewisThomasandSirFrankMacfarlaneBurnetindependentlyconceivedthe‘cancerimmunosurveillance’hypothesis,statingthattumour-associatedneoantigensarerecognizedandtargetedbytheimmunesystemtopreventcarcinogenesisinamannersimilartograftrejection1.Productiveimmuneresponsesfollowingtumouraladoptivetransferinmice4andclinicalreportsofspontaneousregressionofmelanomainpatientswithconcomitantautoimmunedisease5providedadditionalevidencesupportingthishypothesis,althoughaunifyingmechanismwaselusive.Theadventofknockoutmousemodelsprovidedthenecessarytechnologytoexperimentallydemonstratealinkbetweenimmunodeficiencyandcancer6.Additionalmolecularandbiochemicaladvancesledtotheidentificationoftumour-specificimmuneresponses7.Thisprovidedunequivocalevidencethattheimmunesystem,inparticularTcells(seeBox 1andFig. 1),wascapableofwagingwaroncancertissue7.Cancerimmunotherapyhasnowrevolutionizedthefieldofoncologybyprolongingsurvivalofpatientswithrapidlyfatalcancers.Thenumberofpatientseligibleforimmune-basedcancertreatmentscontinuestoskyrocketasthesetherapiespositionthemselvesasthefirstlineformanycancerindications.Noveltreatmentcombinationsandnewlyidentifieddruggabletargetswillonlyexpandtheroleofimmunotherapyinthetreatmentofcancerinthedecadestocome.Fig.1:PeripheralTcellfatesafterantigenicactivation.RestingTcellsbecomeactivatedafterstimulationbycognateantigeninthecontextofanantigen-presentingcellandco-stimulatorysignals.ActivatedTcellsproduceandconsumeproliferative/survivalcytokines,forexample,IL-2,IL-4andIL-7,andbegintoexpandinnumber.IfCD4+CD25+regulatoryT(Treg)cellsarepresent,theycandeprivethecyclingTcellsofproliferative/survivalcytokines,especiallyIL-2,causingthemtoundergoapoptosis.Oncecellsareproliferatingrapidly,theyhavedifferentfatesdependingontheirenvironment.Iftheyreceiveacutestrongantigenicstimulation,especiallyifitisencounteredrepeatedly,thecellswillundergorestimulation-inducedcelldeath.Bycontrast,iftheyreceivechronicweakantigenicstimulation,thecellswillsurvivebutbecomereprogrammedintoaspecificunresponsivetranscriptionalstateknownas‘Tcellexhaustion’.Finally,astheantigenandcytokinestimulationdiminishesastheimmuneresponsewanes,usuallyoncethepathogenhasbeencleared,cytokinewithdrawalcanoccurpassivelytocontracttheexpandedpopulationofantigen-specificTcells.Asmallfractionofcellswillbereprogrammedtoentera‘memory’phenotype,andthisdifferentiationstepisfacilitatedbyIL-7andIL-15.MemoryTcellswillcontinuetopersistintheimmunesystemandformthebasisofanamnesticresponses.Intheseregulatoryprocesses,Tcelldeathusuallytakestheformofapoptosis.FullsizeimageInthisReview,weemphasizetheroleofTcellsinmoderncancerimmunotherapiesanddiscussthreedifferentcategoriesofimmunotherapeuticapproachestotreatcancer:immunecheckpointblockade,anapproachthatisdesignedto‘unleash’powerfulTcellresponses;adoptivecellulartherapies,whicharebasedontheinfusionoftumour-fightingimmunecellsintothebody;andcancervaccines,whichcanbedesignedtohaveeitherprophylacticortherapeuticactivity.Finally,weintroducesomeoftheemergingtargetsandapproachesincancerimmunotherapy.Box1Tcellfunction,development,activationandfateThe1960srepresentedaperiodofenlightenmentwithinthefieldofimmunologybecausetwomajorsubtypesoflymphocytes,BlymphocytesandTlymphocytes,werecharacterized264,265.Thiswasrecognizedbythe2019LaskerAwardforBasicScience,awardedforthepioneeringworkbyJacquesA.F.P.MillerandMaxDaleCooperthatdefinedthekeyrolesofTcellsandBcellsinadaptiveimmunity.Bcellsrecognizecirculatingantigeninitsnativeformandrespondbysecretingprotectiveantibodies266.Bycontrast,Tcellsrecognizepeptideantigens,derivedfromproteinsdegradedintracellularly,thatareloadedontocellsurfaceMHCmolecules,aprocesscalledantigenpresentation.TwobroadclassesofTcellsthathavedistincteffectormechanismsaredelineatedbytheexpressionofeithertheCD4orCD8co-receptor:CD4+TcellsdetectantigeninthecontextofMHCclassIImoleculesandorchestratetheadaptivearmoftheimmunesystembyproducingcytokineswithchemotactic,pro-inflammatoryandimmunoprotectiveproperties267.AtleastoneCD4+Tcellsubclass,CD4+CD25+regulatoryTcells,dampenstheimmuneresponsefollowingchallenge268.CD8+TcellsdetectantigeninthecontextofMHCclassImoleculesandcarryoutdirectcytotoxicreactionsthatkillinfectedorneoplasticcells269.Auniqueclone-specificcellsurfaceproteincomplex,theTcellreceptor(TCR),specificallyrecognizesantigensandparticipatesinthedevelopmentalselectionofTcellsthatcanrecognizepathogensbutareself-tolerant270.TheTCRcomplexcompriseshighlypolymorphicsingleα-andβ-glycoproteinchains(asmallTcellpopulationharboursγ-andδ-chainsinstead)thatcontainvariableandconstantregions,akintoimmunoglobulins,andagroupofnon-polymorphicsignallingchains,calledCD3γ,δ,εandζ.AvastrepertoireofTcellclonotypeswithuniquespecificitiesisgeneratedthroughrearrangementofα-andβ-chaingenesegmentswithinthegenomeofeachTcell271.Followingclonotypeproduction,positiveandnegativethymicselectionfunctionstoentraina‘tolerant’immunesystem,onethatefficientlyrespondstopathogensorcancercellsbutgenerallyignoresor‘tolerates’self-tissuesasnon-immunogenic269,270.AntigenstimulationoftheTCRisnecessaryforTcellactivationandproliferation,butanadditionalsignal,termedco-stimulation,isrequiredforphosphorylationeventscrucialforearlysignaltransduction272.Thenon-polymorphicsurfaceproteinCD28anditsfamilymembersarethemostpotentco-stimulatoryreceptorsonTcells,aselegantlydemonstratedbythesynergismofanti-CD28stimulatoryantibodiesandTCRengagementonTcellactivationandproliferation273,274.AdditionalevidencewasprovidedbystudiesdemonstratingtheefficientinhibitionofTcellactivationandproliferationbyinhibitoryanti-CD28antibodies275,276,277,278.TheligandsforCD28,B7-1andB7-2,areexpressedonantigen-presentingcellsandareupregulatedwhenthesecellsencountermicroorganismsthatactivateToll-likereceptorsorotherpathogensensors279,280.Inhibitorymolecules,includingcytotoxicTlymphocyte-associatedprotein4(CTLA4)andprogrammedcelldeath1(PD1),areinducedduringimmuneresponsesandrepresenta‘checkpoint’todampenTcellhyperactivation281(seeFig. 2).ThepolymorphicTCRsignalsthroughacomplexofthreesetsofdimericCD3chains,ε–δ,γ–δandζ–ζ282.TheintracellularportionsoftheCD3chainscontainimmunoreceptortyrosine-basedactivationmotifsthatarephosphorylatedbylymphocyte-specificproteinkinase(LCK),aSRCfamilykinase283.Atrest,thesurfacesignallingproteinCD45exhibitsphosphataseactivitythatblocksLCKfunction284.Followingactivation,CD45removesaninhibitoryphosphateonLCK,permittingphosphorylationofζchain-associatedproteinkinase70(ZAP70),aSYKkinasefamilymemberthatbindstoimmunoreceptortyrosine-basedactivationmotifsintheCD3ζ-chainandrecruitsthelinkerforactivationofTcells(LAT)andphospholipaseCγ1(PLCγ)285.Withampleco-stimulation,downstreamsignallingaffectscalciumrelease,theactivationoftheGTPaseRASandtranscriptionalreprogrammingessentialforactivatedTcellfunction286.Followingactivation,circulatingnaiveTcellshavethreemajorfatesintheperiphery(Fig. 1).First,theeffectorTcellpopulationcancontractthroughapoptosisastheimmuneresponseresolves(cytokinewithdrawal)orfollowingrepeatedhigh-dosestimulation(restimulation-inducedcelldeath)287,288,289.Tcellscanalsoexhibitanexhaustedphenotypeinducedbyrepeatedlow-doseandlow-affinitystimulation,asseeninchronicinfectionsandneoplasticprocesses88.Lastly,asubsetoftheseeffectorcellsareinvolvedinlong-termimmunologicalmemory.MemoryTcellsareprimedtoreactmorevigorouslytothesameantigenduringasubsequentencounter,makingthemcriticalmediatorsofimmunerecallresponsestopathogensandtumours290.Leveragingthepoweroftechnologicaladvancesinmolecularbiology,recentsingle-cellRNAsequencingandepigenomicstudieshaveprovidedadditionalmolecularinsightintoTcellfatesandthecorrespondingfeaturesofimmunotherapy-responsiveTcells.Thesestudiescollectivelyimplicatethatcomplextranscriptomic,epigenomicandclonotypicchangesoftumour-infiltratingTcellsdeterminethesuccessofimmunotherapy291,292,293,294.ImmunecheckpointtherapySeveralevolutionarilyconservednegativeregulatorsofTcellactivationactas‘checkpointmolecules’tofine-tunetheimmuneresponseandregulatehyperactivation.CytotoxicTlymphocyteantigen4(CTLA4)andprogrammedcelldeath1(PD1)arethemostpotentexamplesofTcellimmunecheckpointmolecules.TheyexerttheirbiologicaleffectatdistinctbodysitesandtimesduringtheTcelllifespan8.Therefore,theycomplementeachotherfunctionallyandensurethatTcellresponsespreserveself-tolerancewhileeffectivelyprotectingthebodyfrompathogensandneoplasia.CTLA4andPD1havebeensuccessfullytargetedbyseveralpioneeringresearchgroupsastreatmentsforawidevarietyofrecalcitrantcancers,researchthatultimatelyearnedJamesP.AllisonandTasukuHonjothe2018NobelPrizeinPhysiologyorMedicine.CTLA4biologicalfunctionAfterthediscoveryofTcellco-stimulationmediatedbythesurfaceproteinCD28(Box 1),thesearchforadditionalimmuneregulatorsledtotheidentificationofCTLA4,areceptorwithstructuralandbiochemicalsimilaritiestoCD28,asanewimmunoglobulinsuperfamilymember9,10.TheCTLA4andCD28genesarefoundinthesameregionofchromosome2(2q33.2)andareselectivelyexpressedinthehaematopoieticcompartment11.However,incontrasttothehighlevelsofbasalCD28expressiononconventionalTcells,CTLA4isexpressedatalowbasallevelandisstronglyinducedfollowingantigenactivation.Interestingly,CD4+CD25+regulatoryT(Treg)cells,whichhaveanimmunosuppressivefunction,expressCTLA4constitutively.Structurally,bothCTLA4andCD28formmembrane-boundhomodimerscomprisinganextracellularimmunoglobulin-likedomain,atransmembraneregionandacytoplasmictailcapableofrecruitingsignallingproteinsandcontrollingsurfaceexpression10,12,13.ThetraffickingofCTLA4-containingvesiclestothecellsurfaceafteractivationiscontrolledbyaphysicalinteractionwiththelipopolysaccharide-responsiveandbeige-likeanchorprotein(LRBA)13.ThesequencesimilaritybetweenCTLA4andCD28ishighestwithintheirextracellularbindingdomainandtheythereforebindtothesameligands,calledB7-1(alsoknownasCD80)andB7-2(alsoknownasCD86),whichareexpressedbyantigen-presentingcells(APCs;Box 1).However,CTLA4hasgreateraffinityandaviditythanCD28forB7ligands,representingakeydifferenceintheirbiology14,15,16.Withfurthercharacterization,itbecameclearthatCD28andCTLA4hadoppositeimmunoregulatoryfunctions.Forexample,solubleCTLA4wasshowntoinhibittheproliferationofTcellsco-culturedwithB7-expressingAPCsbecauseitinterferedwiththeCD28–B7interaction14.Tcellreceptor(TCR)signallingstudiesunequivocallydemonstratedthatCTLA4inhibitsTcellactivationandproliferation12,17,18.ThenegativetolerogenicroleofCTLA4wasalsoevidentinvivo,becauseCtla4-knockoutmicedevelopedacharacteristicTcell-mediatedlymphoproliferativeautoimmunedisease19.TheabsenceofCtla4wassufficienttocausethisphenotype,astreatmentwithanengineeredsolubleversionofaCTLA4:Fcfusionprotein(CTLA4Ig)andgeneticcrossestoB7-deficientmiceameliorateddisease20,21.TheautoimmunelymphoproliferativedisordercausedbyCtla4lossdependsontheactivityofCD28becausemutationofanLCK-bindingcarboxy-terminalprolinemotifintheintracellulartailofCD28abrogatesdiseaseinmousemodels22.Moreover,humanpatientswithCTLA4haploinsufficiencyexhibitsimilarseveremultiorganlymphocyticinfiltrationandautoimmunity(CHAIdisease)thatcanbetreatedwithabatacept,anFDA-approvedCTLA4Ig23,24.CTLA4restrainsTcellactivationthroughmultiplemechanisms:bydirectlyantagonizingCD28,bycompetingforco-stimulatoryligands,bypreventingimmuneconjugateformationandbyrecruitinginhibitoryeffectors25(Fig. 2).TodirectlyopposeCD28activity,intracellularvesiclesreleaseCTLA4attheimmunologicalsynapsewhereitassociateswiththeTCR26.Inthecontextoftheimmunologicalsynapse,CTLA4canalsoreorganizethecytoskeletonanddisturbTcell–APCimmuneconjugateformation27.CTLA4alsomediatestheinternalizationofitsligands,therebypreventingtheirbindingtoCD28,which,inturn,reducesIL-2secretionandTcellproliferation17,28,29.Lastly,phosphatases,includingSH2domain-containingtyrosinephosphatase2(SHP2)andproteinphosphatase2A(PP2A),arerecruitedandinteractwiththecytoplasmictailofCTLA4,therebycontributingtoitsnegativeeffectonTcellactivation.SHP2isaninhibitorofphosphorylationoftheCD3ζ-subunitoftheTCRandalsoinhibitsphosphorylationoftheadaptorproteinlinkerofactivatedTcells(LAT)30,31.PP2Aishypothesizedtoinhibitextracellularsignal-regulatedkinase(ERK),akinasethatactsasasignallingproteindownstreamoftheTCR32.However,thereissignificantdebateaboutwhichofthemoleculesthatassociatewiththecytoplasmictailofCTLA4aremostimportantforinhibitingTcellactivity.Nevertheless,theseinhibitorysignalsreducetheactivationoftranscriptionfactors,suchasactivatorprotein1(AP-1),nuclearfactor-κB(NF-κB)andnuclearfactorofactivatedTcells(NFAT),whichreprogrammesTcellstowardsananergicfate29,33.Fig.2:MechanismsofTcellactivationandregulation.Beforeactivation,antigen-presentingcells(APCs)loadantigenontoMHCmoleculestoprepareforcontactwithaTcellthatdisplaysacognateTcellreceptor(TCR)whilealsoprovidingnecessaryco-stimulatoryligandsB7-1andB7-2.TheinhibitorymoleculecytotoxicTlymphocyteantigen4(CTLA4)iscontainedwithinintracellularvesiclesinnaiveTcells,whereasitisconstitutivelyexpressedonthecellsurfaceofCD4+CD25+regulatoryT(Treg)cells.BothclassesofTcellsexpresstheco-stimulatoryreceptorCD28.Earlyafteractivation,generallyinthelymphoidtissue,TcellsareactivatedwhentheirTCRsbindtotheircognateantigenpresentedbyAPCsinconjunctionwithCD28bindingtoB7-1/B7-2.Also,theactivatedTcellsbegintheprocessofdisplayingCTLA4onthecellsurface.TcellswithinperipheraltissuesupregulatePD1atthemRNAlevelearlyafteractivation.Lateafteractivation,inlymphoidtissue,CTLA4expressedbyactivatedTcellsbindstotheB7-1andB7-2moleculesonAPCs,therebypreventingtheirbindingtoCD28andpromotinganergybydecreasingtheTcellactivationstate.Atthesametime,constitutiveexpressionofCTLA4onTregcellsleadstotrans-endocytosisofB7ligandsandinterfereswiththeCD28co-stimulatoryabilityofAPCs.Lateafteractivationinperipheraltissues,PD1isfurtherupregulatedtranscriptionally,leadingtogreatersurfaceexpressionofprogrammedcelldeath1(PD1),whichbindstoitsligandsPDL1andPDL2,therebypromotingTcellexhaustionatsitesofinfectionorwhenconfrontedwithneoplasms.ImagecourtesyoftheNationalInstituteofAllergyandInfectiousDiseases.FullsizeimageBeyonditsfunctioninactivatedconventionalTcells,CTLA4expressiononTregcellsisessentialforthedirectandindirectimmunosuppressiveactivityofthesecells34,35.InvitrostudiesshowedthatCTLA4wasnecessaryforanti-inflammatorycytokinereleasebyTregcells,whichreducespolyclonalactivationandproliferationofconventionalTcellsnearby36,37.ThisresultwasconfirmedinvivobyadoptivetransferofCTLA4-bearingTregcellstopreventautoimmunityinducedbyCTLA4-deficientTcellsthathadbeentransferredtoTcell-andBcell-deficientmice(Rag–/–mice)38,39.Thistreatmenteffectwasnullifiedbyantibody-mediatedneutralizationofCTLA4(refs38,40,41).Thus,Tregcell-expressedCTLA4cancompensateforlackofCTLA4expressionbyconventionalTcells42,43.Beyonddirectimmunosuppression,TregcellsalsoprimedendriticcellstoinduceanergyofconventionalTcellsinaCTLA4-dependentfashionbybindingtoB7ligandsonAPCs,followedbyinternalizinganddegradingthem,aprocesstermedtrans-endocytosis28,44.CTLA4blockadeincancerTherecognitionofCTLA4asanegativeregulatorofTcellactivationgaverisetotheideathatblockingitsactionscouldunleashatherapeuticresponseofTcellsagainstcancer45(Fig. 3).JamesAllisonandcolleaguesfirsttestedthisideaanddemonstratedthatneutralizinganti-CTLA4antibodiesenhancedantitumouralimmunityinmiceagainsttransplantedandestablishedcoloncarcinomaandfibrosarcoma46.Inaddition,duringrechallenge,animalstreatedwithanti-CTLA4wereabletorapidlyeliminatetumourcellsthroughimmunemechanisms,providingevidencethatblockingofCTLA4induceslong-lastingimmunologicalmemory46,47.AlthoughCTLA4-targetedmonotherapywasshowntoconferbenefitinanimalmodelsofbrain48,ovarian49,bladder50,colon46,prostate47andsofttissue46cancers,lessimmunogeniccancers,includingSM1mammarycarcinoma51andB16melanoma52,didnotrespondasfavourably.Furthermore,heterogeneitybetweencancermodelsyieldeddiscordanttissue-specificresults45,53.Inaddition,agreatertumourburdencorrelatedwithreducedtumourresponsestoanti-CTLA4treatmentbecauselargertumoursfosteramorerobustanti-inflammatorytumourmicroenvironment45,49.Fig.3:EffectsofCTLA4-blockingantibodies.CytotoxicTlymphocyteantigen4(CTLA4)-blockingantibodies(α-CTLA4),especiallywhenboundtoanFcreceptor(FcR)onanantigen-presentingcell(APC),canpromoteantibody-dependentcellularcytotoxicity(ADCC).CD4+CD25+regulatoryT(Treg)cellsexpresshigheramountsofCTLA4thanconventionalTcellsandarethereforemorepronetoα-CTLA4-inducedADCCthanconventionalTcells.Inaddition,α-CTLA4canbindtoCTLA4onthesurfaceoftheTregcellandpreventitfromcounter-regulatingtheCD28-mediatedco-stimulatorypathwaysthatareplayingaroleinTcellactivation.Atthesametime,α-CTLA4canalsopromoteTcellresponsesbyblockingCTLA4onthesurfaceofconventionalTcellsastheyundergoactivation.TCR,Tcellreceptor.Adaptedfrom©2019Fritz,J.M.&Lenardo,M.J.OriginallypublishedinJ.Exp.Med.https://doi.org/10.1084/jem.20182395(ref.135).FullsizeimageDespitethemixedsuccessinpreclinicalstudies,mAbstargetingCTLA4provedeffectiveinclinicaltrialsofmelanoma45.Ipilimumab,ahumanIgG1κanti-CTLA4mAb,gainedFDAapprovalin2011fornon-resectablestageIII/IVmelanomafollowingevidencethatitelicitedpotenttumournecrosis54andconferreda3.6-monthshort-termsurvivalbenefit55.Long-termsurvivaldatademonstratedthat22%ofpatientswithadvancedmelanomatreatedwithipilimumabbenefitedfromanadditional3yearsormoreoflife56.Additionallong-termstudieshavedemonstratedthedurabilityofthissurvivalbenefit,indicatingthepersistenceofantitumouralimmunityfollowingCTLA4blockade56,57.Unfortunately,trialresultsinrenalcellcarcinoma58,non-small-celllungcancer59,small-celllungcancer60andprostatecancer61haveyieldedlessimpressiveeffectsthanthoseseeninpatientswithmelanoma.Tremelimumab,anIgG2isotypeformofaCTLA4-blockingantibody,hasyettoreceiveFDAapprovalasitdidnotincreasesurvivalinadvancedmelanoma62.Itishypothesizedthateffectivenessvariesbetweenipilimumabandtremelimumabowingtodifferencesinbindingkineticsandthecapacitytomediateantibody-dependentcell-mediatedcytotoxicity63,64.ThemechanismsofCTLA4-mediatedtumourregressionarepleiotropicbutunifiedbytheactionofonecelltype,theTlymphocyte(Fig. 3).TcellresponsesarenecessaryforthetherapeuticeffectsofCTLA4-targetedagentsbecauseTcelldepletioninanimalmodelsabolishestumoricidalactivity65.InhibitionofCTLA4enhancesTcellclonalresponsestotumour-associatedneoantigensandahighneoantigenburdenportendsafavourableresponsetoanti-CTLA4therapy66,67.ApartfromboostingeffectorTcellresponses,anti-CTLA4therapydepleteslocalintratumouralTregcellsthroughantibody-dependentcell-mediatedcytotoxicityinmousemodelsandshiftsthebalanceofthetumourmicroenvironmentawayfromimmunosuppression68,69.Thisphenomenonrequiresfurtherstudyinhumancancerascurrentdataareinconclusive70,71.TherelativeroleofeffectorTcellsandTregcellsinconferringaclinicalbenefithasbeencontested,althoughspecificblockingofCTLA4inbothcellpopulationscanleadtosynergisticincreasesintumourregression69.Overall,currentdatasuggestthatthemostcriticalfactorinpredictingoutcomeistheratioofeffectorTcellstoTregcellsinfiltratingthetumour45,49.PD1/PDL1biologicalfunctionPD1wasfirstidentifiedin1992asaputativemediatorofapoptosis,althoughlaterevidencesuggestedaroleinrestrainingimmunesystemhyperactivation,analogoustoCTLA4(ref.72).Asatype1transmembraneglycoproteinwithintheimmunoglobulinsuperfamily,PD1exhibitsa20%and15%aminoacididentitytoCTLA4andCD28,respectively73.HumanPD1isexpressedonTcellsafterTCRstimulationandbindstheB7homologuesPDL1(alsoknownasB7-H1)andPDL2(alsoknownasB7-DC),whicharepresentconstitutivelyonAPCsandcanbeinducedinnon-haematopoietictissuesbypro-inflammatorycytokines74,75,76.Inthisreview,werefertoPD1anditsligandsasthe‘PD1axis’.ThepredominantroleofthePD1axisinthenegativeregulationofTcellactivationbecameclearin1999whenlossofthemousePD1orthologue,Pdcd1,wasfoundtocauseautoimmunityinvivo.C57BL/6micelackingfunctionalPD1proteindevelopedsplenomegaly77.AgeingoftheseanimalsledtomildTcell-mediatedlupus-likeglomerulonephritisandarthritisthatwasexacerbatedbyconcurrentlprmutationsintheFasgene78.CharacterizationofadditionalmousestrainsshowedthatPdcd1–/–miceoftheBALB/cstrainexhibitedcardiacinflammationleadingtodilatedcardiomyopathy79.Bycomparison,non-obesediabeticPdcd1–/–micehadacceleratedtype1diabetesmellituscomparedwiththeirPdcd1-sufficientcounterparts80.Theheterogeneousandlate-onsetautoimmunephenotypesofPdcd1–/–miceweredistinctfromCtla4–/–animals,demonstratingthatthePD1axisregulatesTcellbiologydifferentlytoCTLA4.Spatially,CTLA4exertsitsregulatoryeffectpredominantlywithinlymphoidorgans,whereasPD1tendstowardstemperingTcellactivationlocallywithinperipheraltissues8.Temporally,PD1actslaterinthecourseofTcellactivationandfatedetermination.Overall,thePD1axisplaysauniqueroleinmaintainingTcelltolerancetoself.PD1restrainsimmuneresponsesprimarilythroughinhibitoryintracellularsignallingineffectorTcellsandTregcells81.Theimmunoreceptortyrosine-basedswitchmotifandtheimmunoreceptortyrosine-basedinhibitorymotifofPD1arephosphorylatedandrecruitthephosphatasesSHP1andSHP2,whichdephosphorylate,andtherebyinactivate,downstreameffectors(thatis,theCD3ζ-subunitandZAP70)thatareimportantforearlyTcellactivation76andCD28signalling82.BothCTLA4andPD1inhibitproteinkinaseB(PKB;alsoknownasAKT)signallingtoreduceglucoseuptakeandutilization,theformerthroughPP2Aandthelatterbyreducingphosphoinositide3-kinase(PI3K)activity83.IncontrasttoCTLA4,thePD1axisisessentialforcontrollingthecontinuedactivationandproliferationofdifferentiatedeffectors;whenPD1engagesitsligands,itcaninduceastateofTcelldysfunctioncalledTcellexhaustion84,85,86.However,whatdetermineswhetherPD1mediatesexhaustionorapoptosisincertaincontextsisstillanactiveareaofresearch.OnemodelsuggeststhattheinteractionbetweenPI3KsignallingandthemitochondrialBcelllymphoma-extralarge(BCL-XL)proteinisacriticalcontrolpointatwhichPD1-mediatedP13KinhibitionreducesBCL-XLandpromotesapoptosis25,83.BeyondregulatingconventionalTcells,PDL1onAPCscancontrolTregcelldifferentiationandsuppressiveactivity87.Unfortunately,tumourcellscanexploitthismechanismbyupregulatingPD1ligandstoinduceTcellexhaustionandgenerateatumourmicroenvironmentthatfacilitatestumourgrowthandinvasion88.PD1/PDL1blockadeincancerOncethePD1axiswasimplicatedinthenegativeregulationofTcells,preclinicalworkexaminedwhetherinhibitorsofthispathwaycouldbeusedforcancertreatmentandbiomarkerdiscovery.First,overexpressionofPDL1orPDL2incancercelllineswasfoundtoconstraintheCD8+Tcellcytotoxicantitumourresponse,whereastumourswererejectedinmicewithoutfunctionalPD1(refs89,90).Second,blockadeofPD1suppressedthegrowthoftransplantedmyelomacellsinsyngeneicanimals90.Conversely,transplantedcellsoverexpressingPDL1orPDL2insyngeneicmiceallowedforincreasedtumourcolonization,burdenandinvasiveness90.NeutralizingthePD1axisusingmAbs89,91orsecretedPD1extracellulardomains92reversedtheseeffectsandenhancedTcellcytotoxicitytowardstumourcells90(Fig. 4).RescuingCD8+TcellcytotoxicitybyPD1blockadedependsontheexpressionofCD28asPD1-mediatedimmunomodulationislostinthecontextofCTLA4Ig,B7blockadeorCD28conditional-knockoutmice92.Inaddition,reinvigoratedTcellsintheperipheralbloodofpatientswithlungcancerfollowingPD1blockadewereshowntoexpressCD28(ref.93).PD1inhibitionnotonlyaugmentsantitumouralimmunitybutalsolimitshaematogenousseedingofB16melanomaandCT26coloncarcinomametastasesinmousemodels94.Thus,PD1/PDL1blockadecanbothenhancetumourcytolysisandlimitmetastasis.ApartfromaroleofPD1anditsligandsincancertreatment,multiplestudieshavealsoshownanegativecorrelationbetweenhumantumourexpressionofproteinsinvolvedinthePD1axisandprognosis,indicatingtheutilityoftheseproteinsaspotentialbiomarkers95,96,97.Fig.4:MechanismsofPD1axisinhibition.ActivatedTcellsexpressprogrammedcelldeath1(PD1),whichengageswithitsspecificligand(PDL1orPDL2)todampenactivation.BlockingofthePD1axisthroughtheadministrationofananti-PD1(oranti-PDL1oranti-PDL2)antibodypreventsthisinhibitoryinteractionandunleashesantitumouralTlymphocyteactivitybypromotingincreasedTcellactivationandproliferation,byenhancingtheireffectorfunctionsandbysupportingtheformationofmemorycells.Consequently,moreTcellsbindtotumourantigenspresentedontumourcellsbyMHCmoleculesviatheirTcellreceptors(TCRs).Thisultimatelyleadstothereleaseofcytolyticmediators,suchasperforinandgranzyme,causingenhancedtumourkilling.APC,antigen-presentingcell.Adaptedfrom©2019Fritz,J.M.&Lenardo,M.J.OriginallypublishedinJ.Exp.Med.https://doi.org/10.1084/jem.20182395(ref.135).FullsizeimageFollowingpreclinicalsuccess,mAbsdesignedtocounteractnegativeimmunoregulationbythePD1axisweredevelopedandefficacywasshowninclinicaltrials98.DevelopmentwasinitiatedbyMedarex(ultimatelypurchasedbyBristol-MyersSquibb)in2001(ref.99).In2010,aphaseItrialdemonstratedthatPD1blockadewaswelltoleratedandcouldpromoteantitumouralresponses100.In2014,thehumanizedandfullyhumananti-PD1mAbspembrolizumabandnivolumab(bothIgG4)becamethefirstFDA-approvedPD1-targetedtherapeuticsforrefractoryandunresectablemelanoma101,102,103,104.Inahead-to-headcomparison,pembrolizumabshowedbetter6-monthprogression-freesurvivalthanipilimumabandconferredanoverallsurvivalbenefit105,106.Clinicaltrialsofnivolumabdemonstratedanoverallsurvivalof72.9%at1yearcomparedwith42.1%survivalinthegroupofpatientstreatedwiththechemotherapeuticdacarbazine104.In2015,pembrolizumabwasapprovedforthetreatmentofPDL1-expressingnon-small-celllungcarcinomabecauseitprovideda4.3-monthincreaseinprogression-freesurvivalcomparedwithplatinum-basedchemotherapeuticsandwasmoreeffectivethanthechemotherapeuticpaclitaxel107,108.IncreasedPDL1expressiononthetargettumourwasassociatedwithimprovedresponsestoPD1axisblockade109.Additionalsuccessfulclinicaltrialsexpandedtheuseofpembrolizumabtoheadandnecksquamouscellcarcinoma110,Hodgkinlymphoma111,urothelialcarcinoma112,gastric/gastro-oesophagealjunctioncancer113andtissue-agnosticcarcinomawithahighdegreeofmicrosatelliteinstability114.Followingapprovalintissue-agnosticcancerswithmicrosatelliteinstability,pembrolizumabbecamethefirstdrugtobeapprovedbasedonamolecularbiomarkerratherthanbycancersite.However,theimmunosuppressivemicroenvironmentofdifferenttissuesmakesithardtopredictwhichpatientswillbenefit115,116.Similartoprembrolizumab,theuseofnivolumabhassincebeenextendedtorenalcellcarcinoma117,headandnecksquamouscellcarcinoma118,urothelialcarcinoma119,hepatocellularcarcinoma120,Hodgkinlymphoma121andcolorectalcancerwithahighdegreeofmicrosatelliteinstability122.Aswasseenwithanti-CTLA4therapy,long-termsurvivalanalysesdemonstratealong-lastingimmune-mediatedsurvivalbenefitfollowingPD1blockade123.However,thereasonwhyPD1blockadehasdemonstratedbroaderclinicalutilitythananti-CTLA4treatmenthasremainedelusive.ItishypothesizedthatthedifferencemaybebecausethePD1axisisfrequentlyco-optedbytumoursvialigandexpression,whereasCTLA4representsabroaderimmunoregulatorycircuit74,124.PDL1isalsotargetablebyspecificantibodiesthathaveproveneffectivetreatmentsinmultipleformsofcancer.In2016,thefirstPDL1-targetedhumanizedmAb,atezolizumab(anIgG4antibody),wasapprovedfortreatmentofurothelialcarcinoma.Anoverallresponserateof15%wasdeemedstatisticallysignificantbasedonhistoricalcontroldata,althoughresponsesweredependentontumourPDL1expressionstatus125.Unfortunately,additionaltrialdatahavenotdemonstratedthatatezolizumabhasclinicalefficacybeyondthestandardofcareinurothelialcarcinoma,althoughitislesstoxicthantraditionalchemotherapy126.Indicationshavesinceexpandedtoincludethetreatmentofnon-small-celllungcarcinoma127,triple-negativebreastcancer128andsmall-celllungcancer129.Additionalanti-PDL1humanmAbs,avelumabanddurvalumab,enteredthemarketin2017(ref.98).AvelumabisusedforthetreatmentofMerkelcellcarcinoma130,urothelialcarcinoma131andadvancedrenalcellcarcinoma132.Duvalumabisusedforurothelialcarcinoma133andnon-small-celllungcancer134.Therefore,similartoPD1,blockadeofPDL1hasbeeneffectiveindifficult-to-treatformsofcancer.AdverseeffectsofcheckpointblockadeBlockinganaturallyoccurringcentralimmunecheckpointunleashespowerfulimmuneeffectormechanismsthatmaynotrespectthenormalboundariesofimmunetolerancetoself-tissues135.Ctla4-andPdcd1-knockoutmiceprovidedaglimpseintothespectrumofautoimmuneresponsesthatoccurinhumansduringimmunecheckpointblockadetherapy19,77,78,79.Humanloss-of-functionmutationsinCTLA4anditsinteractingregulatoryprotein,LRBA,alsomirrortheimmune-relatedsideeffectsobservedwithanti-CTLA4therapy13,24.Onthebasisofameta-analysisoftrialdatasets,immune-relatedadverseeventsareestimatedtooccurin15–90%ofpatients55.Moresevereeventsrequiringinterventionareobservedin30%and15%ofpatientstreatedwithCTLA4andPD1axisinhibitors,respectively136.ThecommonimmunefeatureoftoxicityisthelossofnaiveTcellsandtheaccumulationofoveractivememoryTcellsthatinvadeperipheralorgans,suchasthegastrointestinaltractandlungs,andcauseinflammatorydamage.Keratinizedandnon-keratinizedmucosaappeartobethemostsusceptible,asapproximately68%and40%oftreatedpatientsexhibitpruritisandmucositis,respectively137,138.Anti-CTLA4therapycarriesanincreasedriskofsevereautoimmunecomplicationscomparedwiththerapiestargetingthePD1axis,aswasobservedinknockoutmiceandinclinicalstudies19,77,78,79,80,139.Inaddition,datafromdose-escalationtrialssupporttheclaimthatanti-CTLA4agentselicitdose-dependentresponsesnotseenwiththerapiestargetedatthePD1axis107,139.Toxicitiesaffectingthegastrointestinaltractandbrainaremorecommonwithanti-CTLA4therapy,whereaspatientstreatedwithPD1axis-targetedtherapiesareathigherriskofhypothyroidism,hepatoxicityandpneumonitis137.However,asthenumberofindicationstreatedwithcheckpointblockadeincreasesandmorepatientsaretreated,rarersideeffectsinawiderspectrumoforgansandheterogeneousresponseshavemanifested137.Forexample,hyperprogressionofdiseasehasbeenobservedinaminorityofpatientswithvarioustumourtypestreatedwithPD1inhibitors140,141,142.Mostrecently,itwasshownthatthePD1inhibitornivolumabcanleadtotherapidprogressionofdiseaseinpatientswithadultTcellleukaemia/lymphoma,providingevidenceforaroleoftumour-residentTregcellsinthepathogenesisofthislymphoma143.Multipleimmune-relatedresponsecriteriahavebeendevelopedtobettercategorizepatientresponsestocheckpointblockade.Inaddition,thesecriteriaaimtodistinguishprogressionfrompseudoprogression,aphenomenoninwhichpatientstreatedwithCTLA4orPD1inhibitorsexperienceaperiodofprogressionfollowedbyrapidtumourclearance144,145.Overall,checkpointblockadeleadstoautoimmunetoxicitieswithatherapy-specificpatternoforganinvolvement,aspredictedbythephenotypesofanimalsgeneticallydeficientforcheckpointmolecules.Interestingly,preclinicalimmunecheckpointtherapystudiesdidnotdemonstratemajoradverseeffectsinvivoand,thus,werenotgreatpredictorsofhumantoxicities146.Thisisthoughttobeduetotheshorttimeframeofthesestudiesandtheinbrednatureofmousestrains146.Recentlydevelopedhumanizedmousemodelsrepresentaplatformthatbetterrecapitulatessideeffectsduetocheckpointtherapy146,147.Nevertheless,toxicityassociatedwithimmunecheckpointblockadeistoleratedbetterthanthetoxicitiesassociatedwithtraditionalchemotherapeutics,makingthesetherapiesattractiveforqualityoflifereasonsbeyondtheirsurvivalbenefit98,148.Recentresearchhasaimedtoimprovetheside-effectprofilesandclinicalresponseofimmunecheckpointblockadethroughthemodificationofexistingantibodiesandtheengineeringofnoveldeliverymethods.ItwasrecentlyshownthatabnormalCTLA4recyclingandsubsequentlysosomaldegradationwasamechanismthatcontributestotoxicitiesandreduceddrugeffectiveness.ModifiedpH-sensitiveantibodiesthatdonotinterferewithLRBA-mediatedCTLA4recyclingwereshowntolimitadverseeventsandimproveclinicaloutcomesinestablishedtumoursinmousemodels,whichmayultimatelybroadenclinicalutility149,150.Additionalresearchhasfocusedondevelopingbiomaterialsforthelocalizedadministrationofcheckpointinhibitors151.Forexample,comparedwithsystemicdelivery,transdermalpatchdeliveryofanti-PD1antibodieswasbettertoleratedandunleashedamorerobustantitumouralresponseinamousemodelofmelanoma151.Abroadfieldofresearchiscurrentlyaimedatdiscoveringnovelmethodstoreducetoxicitiesassociatedwithcheckpointtherapyandtoincreaseclinicalbenefitinagreatervarietyoftumours.Clinicalmanagementofdrug-relatedtoxicitiesisthesameforallcheckpointdrugs,andtoxicitiesaregradedaccordingtothe2009NationalCancerInstituteCommonTerminologyCriteriaforAdverseEventsseverityscale137,152.Mild(grade1)toxicitiesarenottypicallytreated.Inthesettingofgrade2or3adverseevents,checkpointinhibitorsarediscontinueduntilsymptomsandlaboratory-valueabnormalitiesresolve.Glucocorticoidsarealsousedtoeffectivelycontrolimmunehyperactivity.Infliximabandotherimmunosuppressiveagentscanbeusedwhenglucocorticoidsfail.Life-threatening(grade4)toxicitiesnecessitatethecompletediscontinuationoftherapyandtheuseoflife-savingmeasures,asrequired.Activemonitoringofsymptomsandlaboratoryparametersisrecommendedinordertopreventdeathduetocheckpointblockade(grade5).Currentresearchisaimedatidentifyingpredictivebiomarkersfororgan-specifictoxicitiesduetocheckpointtherapy.Forexample,neutrophilactivation,asmeasuredbyincreasedexpressionofthebiliaryglycoproteinCEACAM1andthecellsurfaceglycoproteinCD177,correlateswithgastrointestinal-relatedsideeffectsinpatientstreatedwithipilimumab153.Increasesineosinophilcountsandreleaseofthepro-inflammatorycytokineIL-17areassociatedwithtoxicityregardlessoftheorganaffected154,155.Pharmacogenomicprofiling(usinggeneticinformationtopredictresponsestodrugs)mayprovidemoreinsightintotherelevantgenesandpathwaysmediatingtoxicity137.Ultimately,thehopeisthatgenetic,biochemicalormetabolicprofilingcouldeitherpre-screenorrapidlydetectindividualslikelytoexperiencethemostsevereadversereactionstocheckpointtherapy.AdoptiveTcelltransfertherapyAdoptiveTcell(ATC)therapy,inwhichautologousorallogenicTcellsareinfusedintopatientswithcancer,hasshownconsiderablepromiseinrecentyears.TheviabilityofthistypeoftherapywasfirstshownbySouthametal.in1966,whenhalfofthepatientswithadvancedcancerdemonstratedtumourregressionfollowingco-transplantationwithpatient-derivedleukocytesandautologoustumourcells156.Allogenichaematopoieticstemcelltransplantsforleukaemiarepresentedthefirsteffectiveadoptivetransferapproachdeployedclinically,andclinicalimprovementwasshowntobemediatedbyaTcellgraftversustumourresponse157.ATCwithtumour-infiltratinglymphocytesATCtherapyusingtumour-infiltratinglymphocytes(TILs)forthetreatmentofmetastaticmelanomawaspioneeredattheNationalCancerInstituteinthelate1980s158.LymphocytesisolatedfromacancerbiopsyweregreatlyexpandedwithIL-2andthenreinfusedintravenouslyintothesamepatientwithalargebolusofIL-2.Theobjectiveresponseratewas34%;however,themediandurationofresponsewasonly4monthsandfewpatientsexperiencedacompleteresponse159.LaterstudiesincorporatinglymphodepletionbeforeATCtherapyin93patientswithmetastaticmelanomaweremoresuccessful,withcompletetumourregressionin20(22%)patients,19ofwhomwerestillincompleteremission3yearsaftertreatment160.Thescreeningandenrichingforneoantigen-specificTILs,madepossiblebyhigh-throughputtechnologies,recentlydemonstratedpromiseinapatientwithmetastaticbreastcancer161.Inaddition,knockdownofthegeneencodingcytokine-inducibleSH2-containingprotein(Cish),anegativeregulatorofTCRsignalling,wasshowntoboosttheantitumouralresponseofATCtherapyinmousemodels162.However,inorderforTIL-basedATCtherapytoelicitdurableresponses(Fig. 5),effectorTcellswithantitumouractivitymustbepresentinthetumour,whichisnotthecaseformanycancertypes163.OtherinnovativeapproachestotweakTcellactivityandproliferationmayallowforagreaterpaletteoftreatmentstobedeveloped.Fig.5:AdoptiveTcelltherapy.a|Tumour-infiltratinglymphocytes(TILs)areisolatedfromapatienttumourbiopsyandexpandedexvivowithIL-2.TILsaretheninfusedintoapatientwhohasundergonelymphodepletiontoprovideanicheforthetransferredTILstoexpand,actaseffectorcellsandgenerateimmunologicalmemory.AstheTcellswerederivedfromthetumour,itisassumedthatagoodproportioncanrecognizetumour-associatedantigens(TAAs)orneoantigens.b|ThephysiologicalTcellreceptor(TCR)complexgainsitsspecificityfrompolymorphicα-andβ-glycoproteinchainsthathaveanantigen-bindingportionandaconserveddomainthatassociatewithandsignalthroughagroupofnon-polymorphicproteins,CD3γ,δ,εandζ.BioengineeringoftheTCRα-andβ-glycoproteinantigen-bindingdomain(purple),whilepreservingtheconserveddomains(CαandCβ),allowsforthedevelopmentandexpansionofTlymphocyteswithspecificitytotumourneoantigens.c|Originally,chimericantigenreceptors(CARs)werecomposedofanextracellularsingle-chainfragmentofanantibodyvariableregioncoupledtoaCD3ζ-signallingdomain.Poorexpansionandfunctionalityofthesefirst-generationCARsledtothedevelopmentofsecondandthird-generationCARscontainingintracellularmodulesfromco-stimulatorymolecules(CD28and/or4-1BB)thatprovideadditionalsignalsnecessarytofullyactivatetheTcell.SubsequentgenerationsofCARTcellscontainfurthermodificationstoimproveantitumourefficacy.Forexample,fourth-generation‘armoured’CARTcellshavebeenengineeredtosecretepro-inflammatorycytokines,suchasIL-12,toovercomeimmunosuppressioninthetumourmicroenvironment.Thechimericcytokinereceptor4αβ,comprisingtheectodomainofIL-4RαfusedtotheIL-2/IL-15Rβchain,signalsinresponsetoIL-4,anabundantcytokineinnumeroustumourtypes.VH,variableheavychain;VL,variablelightchain.FullsizeimageEngineeredlymphocytesforATCThechallengesassociatedwithexpandingtumour-specificTcellsinvitroledtothedevelopmentofTCR-engineeredlymphocytes(Fig. 5).However,thesecellsarelimitedtorespondingtotumourantigenspresentedbytheMHC(alsoknownashumanleukocyteantigen(HLA)inhumans)ratherthansurfaceantigensontumourcells163.However,syntheticchimericantigenreceptors(CARs)canbypassMHCrestrictionanddirectspecificcytotoxicitytoatargetmoleculeonthesurfaceofthemalignantcell.IsolatedTcellsfromthepatient(orallogeneicdonor)aregeneticallymodifiedtoexpressCARsandthenexpandedandinfusedintothepatient.ThisovercomestheproblemthattumourcellsoftendownregulateMHCmolecules,whichleavesthecellunabletopresentantigentoconventionalTcells164.CARscompriseanantigen-bindingdomain,mostoftenfromthevariableregionsofantibodies,linkedtosignallingdomainsoftheTCRandvariousco-stimulatorymolecules(Fig. 5).Giventhedomainmodularityofcellsurfacesignallingproteins,mixesandmatchesofextracellulartargetingdomainsandinternalsignaltransductiondomainscanbeassembledusingproteinengineering.ThisoffersmanyoptionstotailorCARstospecifictumours.ThefirstgenerationofCARTcellsreliedonlyontheCD3ζ-chaintosimulateTCRsignalling165,butthisdesignwasineffectiveinclinicaltrialsowingtolimitedTcellproliferationandcytokineproduction166,167.SubsequentgenerationsofCARTcellshavebeenengineeredtoincludedomainsfromCD28,CD40ligandandotherpositiveregulatorsofTcellactivationtopotentiateactivationandcytotoxicityinvivo168,169,170,171.Anengineeredsingle-chainPD1blockerhasalsodemonstratedsimilarenhancedefficacytosecond-generationCARTcellswithsolelyaCD28domain172.EventhoughCARTcellsaretypicallyengineeredusingretroviraltransduction,recentworkhasusedCRISPR–Cas9technology.CRISPR–Cas9canbeusedtoedittheTCRgermlinesequencedirectly,whichcouldleadtomoreuniformCARTcellgenerationand,ultimately,betterefficacy173.AlimitationtothedevelopmentofCARTcelltherapiesistherequirementforadistincttissue-restrictedtargetantigenonthetumourcellsurface.Forexample,CARTcellsdesignedwithspecificityforthecellsurfacemoleculeCD19,whichisexpressedbyallBcells,havebeensuccessfulinthetreatmentofBcellmalignancies.Thefirstclinicaldeploymentofsecond-generationCD19-specificCARTcellsledtodurableresponsesinchroniclymphocyticleukaemia174.AdditionalclinicaltrialsofCD19-specificsecond-generationCARTcellsinBcellacutelymphoblasticleukaemia(B-ALL)ledtoremissioninallpatientswithB-ALLwhoweretested175.Afollow-upreportonpatientswithB-ALLenrolledinthisclinicaltrialshowedcompleteremissionofdiseasein44of53(83%)patientswithamedianfollow-upof29months176.SimilarsuccesseswerereportedforpatientswithdiffuselargeBcelllymphoma177,leadingtoFDAapprovalfortheseBcellmalignanciesin2017.TheclinicalsuccessofCARTcelltherapyforthetreatmentofB-ALLanddiffuselargeBcelllymphomaisdue,inpart,totargetingtheCD19antigen,anidealcandidateowingtoitshighexpressionincertainBcellmalignanciesandspecificitytotheBcelllineage.CrossovertargetingofnormalCD19+Bcellsdoesnothampertherapyorcauseseveresideeffects.However,evenasanidealtarget,CD19antigenlossisacommoncauseoftreatmentfailure.CD22isanotherantigencommonlyexpressedbymalignantcellsinB-ALLandhasshownpromiseasatargetforCARTcelltherapyinaphaseItrial178.Othertargets,especiallytumourneoantigens,arecurrentlybeinginvestigatedforhaematologicalmalignanciesthatdonotexpressCD19,aswellasforsolidtumours179,180.Bcellmaturationantigen(BCMA)-targetedCARTcelltherapyispoisedforFDAapprovalformultiplemyelomain2020onthebasisofpromisingpreclinicalandclinicaldata181,182.However,owingtoreportedpatientrelapses,theinvestigationofadditionaltargetantigenscontinues.Apreclinicalstudyrecentlyidentifiedanothertargetantigen,GPRC5D,withcomparableefficacyandtoxicitytoBCMA-targetedCARTcelltherapy183.Thusfar,CARTcelltherapyhasonlybeenmodestlysuccessfulforsolidtumours184,185,186andinnovativeapproachestoimprovetherapyareunderway179.Arecentlyidentifiedpan-cancertarget,B7-H3(alsoknownasCD276),hasdemonstratedsuccessinmultiplepaediatricsolidtumourmodels187.Inadditiontodirectlyactingascytolyticagents,CARTcellscanalsotargettheunhospitabletumourmicroenvironmentandreviveexhaustedTcells188,189.Forexample,anewgenerationof‘armoured’CARTcellsengineeredtoproduceIL-12canovercomeimmunosuppressionbyTregcellsandmyeloidcellsinthetumourenvironment,promoteCD8+Tcellcytolyticactivity190andenhancemyeloidcellrecruitmentandantigenpresentation191,192.PreclinicalmodelsusingIL-12-expressingCARTcellsthattargettheconservedextracellulardomainofmucin16(MUC16ecto)haveshownpromisingresultsinmodelsofovariancancer,atumourwithpoorprognosisinadvancedstages193,194.AphaseIclinicaltrialiscurrentlyinprogressforpatientswithovarian,fallopianorprimaryperitonealcancer195.TheefficacyofCARTcellsmayalsobestrengthenedthroughco-expressionofachimericcytokinereceptor(4αβ)thatstimulatesproliferationinresponsetoIL-4,acytokinethatisusuallyabundantinthetumourmicroenvironment.PreliminarystudieshaveshownthatthisapproachworksforCARTcellsdirectedagainstdifferenttumour-associatedantigens(TAAs)196andclinicaltrialsareunderwayinheadandneckcancer197.Inaddition,overexpressionofthetranscriptionfactorJUNwasshowntoconferresistancetoCARTcellexhaustion198.Overall,CARTcellshavebeensuccessfulforthetreatmentofBcellmalignanciesanditwillbeexcitingtocontinueresearchonthisnewtreatmentmodalityforintractabletypesofcancer.LimitationsandadverseeffectsofATCsToxicitiescanarisefromCARTcelltherapyandaffectmanydifferentorgansystemswitharangeofseverity199.Patientsmostcommonlyexperiencecytokinereleasesyndrome(CRS)andneurotoxicity200.CRSresultsfromthepowerfulactivationandproliferationofCARTcellsinvivoandtypicallyappearsquicklyaftercelltransfer.Thesymptomsareoftenmildandflu-likebutcanalsobesevereandlife-threatening,involvinghypotension,highfever,capillaryleakage,coagulopathyandmultisystemorganfailure.Seriousneurologicaleventscanalsooccur,suchasCARTcell-relatedencephalopathysyndrome,typicallycharacterizedbyconfusionanddelirium,butsometimesalsoassociatedwithseizuresandcerebraloedema199.Glucocorticoidsarethefirst-linetreatmentformilderformsofCRSandCARTcell-relatedencephalopathysyndrome.Tocilizumab,ahumanizedanti-IL-6antibody,isahighlyeffectivesecond-linetreatmentforCRScausedbyCARTcelltherapy201.OthersideeffectsofCD19-specificCARTcelltherapyincludelymphopeniaandhypogammaglobulinaemia202,whichcanbeeffectivelymanagedwithintravenousimmunoglobulintherapy,similartothetreatmentthatpatientswithprimaryBcellimmunodeficienciesreceive203.Themechanismsbehindthesesideeffectsareunclearandfurtherresearchmayyieldwaystoavoidorminimizetoxicity.RecentdevelopmentofanovelmurinemodelofCRSdemonstratedthatitisnotmediatedbyCARTcell-derivedIL-6butratherbyrecipientmacrophagesthatsecreteIL-6,IL-1andnitricoxide.Therefore,IL-1blockaderepresentsapossiblenovelinterventioninthearmamentariumagainstCRS204.Moreover,aclinicalstudyoflow-affinityCD19-specificCARTcellsdemonstratedreducedtoxicityandenhancedefficacy205.AdditionaleffortstoreducetoxicityinvolvetheengineeringofCARTcellswithmultiplereceptorspecificities206andreducingthehalf-lifeofcellulartoxicitybyusingmRNA-basedmethodsthatallowfortransientreceptorexpression207orincludingsuicidecassettesthatcanbeactivatedbyexogenousagentstoclonallydeletetheinfusedcells208.TheATCapproachnecessitatesapatient-specifictherapydesign,itscostcanbeprohibitive,patientaccesstothetreatmentislimitedandmanufacturingischallenging.IntheUnitedStates,theCARTcelltherapiestisagenlecleucelandaxicabtageneciloleucelhaveadirectcostofUS$475,000andUS$373,000perpatient,respectively209.However,thesevaluesdonottakeintoaccounttheadditionalcostsassociatedwithtreatingthesevereadverseeffectscommontoCARTcelltherapy,whichareestimatedtoincreasedrug-associatedcostsbyUS$30,000ormore209.IncomparisonwithCARTcelltherapy,checkpointblockadehasapricetagofapproximatelyUS$12,500permonth210.PatientaccesstoCARTcelltherapiesalsorepresentsamajorproblemasthereareonlyafewlaboratoriescertifiedtogenerateCARTcellsandonlyafewspecializedtertiarycarecentresabletoadministerthistherapy211.Lastly,variabilityinthemanufacturingofCARTcellsandalackofstandardpracticescancontributetoheterogeneousoutcomes211.CancervaccinesCancervaccinesprompttheimmunesystemtoprotectthebodyfromcancerandfallintotwocategories,prophylacticandtherapeutic.ProphylacticvaccinesagainsthepatitisBandhumanpapillomavirushavebeeninstrumentalinreducingtheincidenceofhepatocellularcarcinomaandcervicalcancer,respectively212.Theseareclassicvaccinesusedtopreventinfectionbyoncogenicviruses.Bycontrast,therapeuticvaccinesaimtoharnesstheimmunesystemtoeliminatedisease-causingcellsthatarealreadyneoplastic212.AnearlyexampleofthisistheuseofthebacillusCalmette–Guérinvaccine,comprisingattenuatedMycobacteriumbovis,whichisgenerallyusedasaprophylactictuberculosisvaccinebuthasalsobeenrepurposedasaprimitivetherapeuticvaccineforbladdercancer213.Historically,thediscoveryofTAAs214,whicharehighlyexpressedontumourcellsandtoalesserextentonnormaltissues,openedthedoorforfurthertherapeuticvaccine-basedapproaches.However,asTAAsareoftenrecognizedbytheimmunesystemas‘self’,viralantigensandneoantigensthatareuniquetoamalignancymaybemoresuitedasvaccinetargets.Earlyvaccinationapproachesinthe1970swerebasedonautologoustumourvaccinesandinvolvedtheadministrationofpatient-derivedtumourcellstogetherwithanadjuvantorvirusinordertoactivatepolyclonalimmuneresponsestoTAAs215.Forexample,autologoustumourcellsinfectedwithNewcastlediseasevirushavebeenusedinonetypeofcancervaccinethathasdemonstratedsuccessinpreclinicalmodelsofmetastaticlymphomaandmelanoma216,217.ModifiedNewcastlediseasevirus-basedvaccineshavebeenengineeredtoexpressgranulocyte–macrophagecolony-stimulatingfactor(GM-CSF)inattemptstoenhanceefficacy218.Synergismofvaccineapproacheswithcheckpointblockadeagentshasalsobeendemonstratedinsomepreclinicalstudiesofmelanoma46,219.NumerousautologoustumourvaccinesarebeinginvestigatedinphaseIIandphaseIIItrialsbuthaveyettoreceiveFDAapproval.Thisapproachsuffersfrommultiplelimitations,mostnotablythedifficultyinobtainingpatient-derivedtumourcellsincertaincancertypes212.Newerapproachesincludethedevelopmentofpersonalizedrecombinantcancervaccinesinformedbynext-generationsequencingofgenomicDNAfromtumours.DevelopmentofpersonalizedrecombinantcancervaccinesVaccinesthatelicitresponsestotumour-derivedneoantigensshouldinducemorerobustimmuneresponsesandcausefewerautoimmune-relatedtoxicitiesthanvaccinesbasedonself-derivedTAAs,astheTcellsthatareactivatedbysuchavaccinewouldnothaveundergonenegativeselectionduringdevelopment.Thesefactors,aswellastheabilitytoidentifyneoantigensthroughnext-generationsequencingofgenomicDNAfromtumours,hasshiftedthefocustoinvestigatingtheclinicalfeasibilityofmakingpersonalizedrecombinantvaccinesthattargetneoantigens.However,althoughahighermutationalburdeninthetumourhasbeenshowntocorrelatewithgreaterimmunogenicityandsurvivalaftercheckpointblockade66,220,onlyasmallpercentageofneoantigensspontaneouslygenerateimmuneresponsesinpatientswithcancer221.Sahinandcolleaguesshowedthatneoantigensidentifiedthroughnext-generationsequencingcangenerateantitumourresponsesinvivo;inmicethatwerevaccinatedwith50differentneoantigens,16wereimmunogenic222,223.Interestingly,mostneoantigensinducedcytokineresponsesfromCD4+TcellsratherthanCD8+Tcells,suggestingthatneoantigensareselectedforMHCclassIIbinding222,223.OtherpreclinicalstudiesdemonstratedeffectiveCD4+andCD8+Tcellresponsestoneoantigenvaccinesinvariouscancertypes223,224,225,226,227.However,recentpreclinicalworkhasalsohighlightedthenon-overlappingroleofneoantigenresponsesmediatedbyCD4+andCD8+Tcells228.Todesignandmanufactureapersonalizedvaccineforclinicaluse,computer-basedalgorithmsareusedtoidentifywhichtumour-derivedpeptidescouldpotentiallyformasuitableTAAortumourneoantigenwiththepatient’sMHCalleles(Fig. 6).Thereareseveraldifferentstrategiestoformulateneoantigen-basedvaccines,includingassyntheticpeptides,mRNA,viralandDNAplasmidsorantigen-loadeddendriticcells,anditisdifficulttodirectlycomparehoweachstrategyinfluencesimmunogenicity229,230.Inonetrialthattestedamulti-peptidevaccinethatincludedupto20personalneoantigens,4of6patientswithmelanomawhoenteredthestudywithstageIIIdiseaseexperiencedcompleteresponseswithnorecurrence25monthspostvaccination,andtheother2patientswithprogressivediseasesubsequentlyunderwentanti-PD1therapythatresultedincompletetumourregression231.Further,ofthe97differentneoantigensthatweretestedforimmunogenicityinthisstudy,60%elicitedCD4+Tcellresponseswhereas15%elicitedCD8+Tcellresponses.Anotherclinicaltrial,whichtestedanRNAvaccinethatencoded10peptidesrepresentingpersonalizedTAAsin13patientswithadvancedmelanoma,achievedsimilarresults232.Fig.6:Personalizedvaccinedevelopment.HealthytissueandtumourtissuefromapatientwithcanceraresubmittedforDNAsequencingandbioinformaticanalysestoidentifygenevariantsthatencodepeptidesthatarespecifictothetumour(neoantigens).Predictionalgorithmsarethenusedtoscreenforneoantigensthatarelikelytostablybindtothepatient’sMHC(alsoknownasHLAinhuman)moleculesandtheirexpressionisvalidatedbysequencingtumourmRNA.Multiplepredictedneoantigensarethenformulatedintovaccines,whichareadministeredtothepatienttogetherwithadjuvants.Posttreatment,thepatientisregularlymonitoredforneoantigen-specificimmuneresponsesandtumourgrowth.FullsizeimagePitfallsandadverseeffectsofcancervaccinesAlthoughtheseearlycancervaccineexperimentshavebeenpromising,challengesremain.Anindividualtumourcanharbourthousandsofsomaticmutationsandpredictingwhichneoantigenscanelicitstrongantitumourresponsesremainsanimperfectart.However,thecurrentmethods,consistingofvalidatingmRNAexpressionofthemutationintumourcellsandusingsoftware/databasestopredictpeptide–MHCbinding,havebeensurprisinglyeffectiveinclinicaltrialstodate229.However,thissuccesshasbeenbiasedtowardsMHCclassI-specificneoantigensaspredictionforMHCclass IImoleculespresentsuniquechallenges.Forexample,theincreaseddiversityofMHCclassIImoleculesandthestructuralnatureoftheiropenbindingpocketmakediscerningapredictablebindingmotifdifficult233.Takentogether,thesedifferencesbetweenMHCclasseshighlighttheparticularneedfornewMHCclassIIpredictionalgorithms.Otherchallengingfactorstoconsiderarethetimeandcostassociatedwithdevelopingbespokevaccines.Currently,developmentandproductionofthesevaccinestakesapproximately4months,and,althoughthedowntimecanbeusedtoinitiateothertypesoftreatment,shorteningthetimespantopersonalizedtreatmentiscritical.Forrapidlygrowingormetastatictumours,monthsmightmatter.Ongoingeffortstoimprovedesignandmanufacturingcouldshortentheproductiontimetoseveralweeks229.Overall,thecomprehensiveidentificationofsomaticmutations,andtheevaluationofpeptidesderivedfromthesemutationstoelicitimmuneresponses,hasrenewedinterestinvaccinationstrategiesforcancertreatment.Eventhoughearlyclinicaltrialsarepromising,extrapolationofthesefindingscouldbemisleadingandadvancedclinicaltrialswillultimatelydeterminetheefficacyofpersonalizedvaccinetherapy.Nonetheless,cancervaccinesareprototypical‘singlepatientandsingledisease’precisionmedicationsandwouldhavebeenintherealmofsciencefictionjustafewdecadesago.Furtherresearchandtechnologicaldevelopmentswillnodoubtleadtogreaterprecisionandeffectivenessandalsoprovideabetterunderstandingofthemechanismsofantitumouralimmuneresponses.EmergingcancerimmunotherapeuticsThemoleculardiversityofgeneticchangesthattransformcellsinhumancancerscreatesaplethoraofdiseasesinvolvingspecifictissuetypesandcancermechanisms.Giventheexcitingadvancesincancerimmunotherapy,variousmodificationstocurrentimmunotherapeuticapproachesarebeingdevelopedandtestedtoaddressthecomplexityofcancerimmunopathogenesisandcancertargetability.CombinationtherapiesFollowingtheclinicalsuccessofcheckpointblockademonotherapy,combinationtherapiesthatcoupleagentswithdistinctmechanismsofactionhaveaugmentedtreatmentsuccessinvariouscancers.Forexample,ipilimumabandnivolumabcombinationtherapyconferredasignificantsurvivalbenefitinpatientswithmetastaticmelanomaandadvancedrenalcellcarcinoma,leadingtoFDAapprovalsfortheseconditions234,235.Thesynergismofanti-CTLA4andanti-PD1therapiesisnotsurprisingbecauseCTLA4andPD1regulateantitumouralimmunityinacomplementarymanner8.CrosstalkbetweentheCTLA4andPD1pathways,mediatedbyCD80andPDL1dimerization,providesadditionalinsightintothemechanismbehindthesuccessofdualtherapy236,237.However,asexpected,combinationcheckpointtherapyalsoincreasestheriskofmedication-inducedtoxicities235.Combiningradiationtherapywithcheckpointblockadeisanothertreatmentoptionforrecalcitranttumours.Theimmunomodulatoryeffectofradiotherapyalonerepresentsadouble-edgedsword.Mechanistically,radiotherapyincreasesthediversityofantitumouralTcellresponsesbyexposingnovelneoantigensatthesametimeasbluntingtheimmuneresponsethroughtheinductionofPDL1expressionontumourcells238.Therefore,andonthebasisofpreclinicaldata,combiningradiotherapywithblockersofthePD1axisrepresentsanattractivesynergisticcombination239.Patientswithmetastaticdiseasemayrepresentatargetpopulationfordeployingthiscombinationasabscopalresponsestoradiotherapyareboostedbycheckpointblockadeformanytumourtypes238,240.Overall,dualcheckpointblockadeandradiation–checkpointpolytherapyrepresentpromisingavenuesforsynergistictherapeuticresponsesbecausethesedrugcombinationsdisplayuniqueandcomplementarypharmacodynamics.NewtargetsforcheckpointblockadeResearchisalsodirectedatnewlydiscoverednegativeregulatorsofTcellactivation,includinglymphocyteactivationgene3(LAG3),Tcellimmunoglobulin3(TIM3),V-domainimmunoglobulinsuppressorofTcellactivation(VISTA),B7-H3andTcellimmunoreceptorwithimmunoglobulinandimmunoreceptortyrosine-basedinhibitorymotifdomains(TIGIT),asadjuvantcancerdrugs241,242,243.LAG3isaninhibitoryligandthatreducesTcellactivationbyblockingCD4contactsitesonMHCclassIIproteinsandisexpressedonactivatedTcellsandTregcells.ItpreventstheoverexpansionoftheTcellcompartmentbyinducingcellcyclearrest244.LikePD1,LAG3isamarkerofTcellexhaustion,whichportendsapoorerprognosiswhenexpressedonTILs245.Multiplestrategiesofblockadehavebeendeveloped,includingaLAG3:IgfusionproteinandLAG3-targetedmAbs246.Inclinicaltrialsinpatientswithrenalcellcarcinomaandpancreaticadenocarcinoma,thesedrugsdidnotsucceedasmonotherapieseventhoughtheyincreasedthefrequencyoftumour-specificTcells246.However,whencombinedwithpaclitaxelformetastaticbreastcancer,50%ofpatientstreatedwithLAG3:Igrespondedtotreatment247.Recentresearchhasdemonstratedthatfibrinogen-likeprotein1(FGL1)activatesLAG3independentlyofbindingMHCclassIImoleculesandinterferencewiththisinteractionisessentialforunleashingpotentantitumouraleffects248.TIM3isanothernegativeregulatoroftheTcellresponse.RatherthaninhibitingcellcycleprogressionlikeLAG3,itregulatesapoptosisfollowinggalectin9 binding249.Itsupregulationcouldrepresentamechanismofresistancetoanti-PD1therapy,makingcombinationtherapyanattractiveoptiontoboosttheeffectivenessofanti-PD1therapy.Inaddition,TIM3expressioncorrelateswithpoorprognosisinnon-small-celllungcancerandfollicularlymphoma,suggestingaroleincancerprogression250.SimilartoTIM3,VISTAisanothermoleculeshowntobeassociatedwithresistancetocurrentcheckpointinhibitorsandhasdemonstratedsynergismwithanti-PD1therapyinmousemodels251,252.B7-H3representsanothertargetablenegativeregulatoroftheTcellresponse.Itishighlyexpressedinmanytumourtypes,includingnon-small-celllungcarcinoma,prostatecancer,pancreaticcancer,ovariancancerandcolorectalcancer241,243.Enoblituzumab,ahumanizedmAbtargetingB7-H3,waseffectiveatinducingantitumouralresponsesinaphaseIstudyofpatientswithvarioustumourtypes253.Dual-affinityretargeting(DART)proteinsthatbindtoB7-H3andCD3,aswellasradioactiveiodine-conjugatedB7-H3mAbs,representadditionalwaystomodulatethispathwayandareinearly-phaseclinicaltesting254,255.Lastly,TIGIT,whichcontainstwoimmunoreceptortyrosine-basedinhibitorymotifsinitsintracellulardomainanddampensTcellhyperactivation,isbeinginvestigatedasacheckpointtarget.ItismorerobustlyexpressedinTILsthaninperipheralcells,makingitanattractivetargetowingtoitsincreasedspecificitycomparedwithothercheckpointmolecules243.PreclinicalevidencedemonstratesthatTIGITblockadeaugmentstheeffectofpre-existingcheckpointinhibitorsandreinvigoratestumour-specificexhaustedTcells250,256.Currently,blockadeofimmunecheckpointsotherthanCTLA4orthePD1axishavenotyetshownmajorclinicalbenefitsassingleagentsbutrathermayincreasetheeffectivenessofpre-existingtreatments.Althoughtheblockingofimmunecheckpointmoleculesreleasespotentantitumouralresponses,thestimulationofTcellco-stimulatoryreceptors,includinginducibleco-stimulator(ICOS),tumournecrosisfactorreceptorsuperfamilymember4(TNFRSF4;alsoknownasCD134),tumournecrosisfactorreceptorsuperfamilymember9(TNFRSF9;alsoknownas4-1BB),glucocorticoid-inducedtumournecrosisfactorreceptor(GITR)andCD27,canalsoamplifytheeffectofexistingimmunotherapies,asshownpreclinicallyandinearly-stageclinicalstudies168,170,171,241,242,243,257.ICOSisamemberoftheCD28familyofco-stimulatorymoleculesthatmediatescontext-dependentcytokineresponseswithanemphasisonThelper2(TH2)cellskewing258.ICOSstimulationbyvaccinesmodifiedtoexpressICOSligandexhibitedsynergismwithtreatmentwithCTLA4-blockingantibodiespreclinically259.ICOSupregulationfollowingtreatmentwithcurrentlyapprovedanti-CTLA4andanti-PD1therapiesmayrepresentabiomarkerofactiveantitumouralresponsesbecauseitassociateswithfavourableoutcomes260.TNFRSF4isanotherco-stimulatorymoleculeforwhichpreclinicalevidenceindicatesaroleindeployingrobustantitumouralresponsesinsarcoma,melanomaandbreastcancer261,262.DatasuggestthattargetingTNFRSF4amplifiesanti-PD1therapybecauseTNFRSF4agonismcanupregulatePDL1expression263.Inadditiontosynergismwithcheckpointblockade,TNFRSF4upregulationwithinCARTcellsbytransfectionrepresentsawaytoaugmenttumourcytotoxicity170.AgonismofadditionalTNFRfamilymembers,suchasTNFRSF9,GITRandCD27,isbeingtestedasadjuvanttherapyinphaseI/IItrialsforvarioustumourtypes,withpromisingresults243.Therefore,agonismofpositiveTcellco-stimulatorysignals,inconcertwiththeexistingcheckpointinhibitorsorCARTcells,representsanoveltherapeuticavenuetoboostantitumouralimmunity.ConcludingremarksCancerimmunotherapyfocusedonTcellshasemergedasapowerfultoolinthearmamentariumagainstcancer.Nevertheless,ittookmanyyearsofbasicsciencediscoveriesandsubsequentclinicaltranslationtounequivocallydemonstratethepowerofmodulatingtheimmunesystemtotreatcancer.FurtherresearchthatinvestigatestheregulationofTcellsandotherimmunecells,forexampleAPCsandnaturalkillercells,mayallowustoenhancethepowerofthisapproach.In‘difficulttotreat’tumours,theeffectsizesobservedinclinicaltrialsofcheckpointblockadeagents,ATCtransfertherapiesandcancervaccineshavebeenfarhigherthanthemosteffectivechemotherapeuticagents.Althoughimmune-relatedadverseeffectsarecommon,theseinnovativeimmune-targetingtherapiesarebettertoleratedthantraditionalchemotherapeuticagents.Theburgeoningfieldofcancerimmunotherapycontinuestogrowasindicationsforcurrentlyapprovedtherapiesexpandandthesearchfornoveldruggabletargetscontinues.Thecancerimmunotherapysuccessstorieswehaverecountedhighlighttheintrinsicconnectionbetweenbasicscienceresearchandclinicalpractice.Theyalsoillustratehowabench-to-bedsideapproach,builtuponasolidbasicsciencefoundation,canbesuccessfulinfightingoneofhumanity’smostdreadeddiseases. ReferencesOiseth,S.J.&Aziz,M.S.A.-E.Cancerimmunotherapy:abriefreviewofthehistory,possibilities,andchallengesahead.J.CancerMetastasisTreat.3,250–261(2017).CAS  GoogleScholar  Decker,W.K.&Safdar,A.Bioimmunoadjuvantsforthetreatmentofneoplasticandinfectiousdisease:Coley’slegacyrevisited.CytokineGrowthFactor.Rev.20,271–281(2009).PubMed  GoogleScholar  Decker,W.K.etal.Cancerimmunotherapy:historicalperspectiveofaclinicalrevolutionandemergingpreclinicalanimalmodels.Front.Immunol.8,829(2017).PubMed  PubMedCentral  GoogleScholar  Gross,L.IntradermalimmunizationofC3Hmiceagainstasarcomathatoriginatedinananimalofthesameline.CancerRes.3,326(1943). GoogleScholar  Smith,J.L.Jr.&Stehlin,J.S.Jr.Spontaneousregressionofprimarymalignantmelanomaswithregionalmetastases.Cancer18,1399–1415(1965).PubMed  GoogleScholar  Chow,M.T.,Moller,A.&Smyth,M.J.Inflammationandimmunesurveillanceincancer.Semin.CancerBiol.22,23–32(2012).CAS  PubMed  GoogleScholar  Halliday,G.M.,Patel,A.,Hunt,M.J.,Tefany,F.J.&Barnetson,R.S.C.Spontaneousregressionofhumanmelanoma/nonmelanomaskincancer:associationwithinfiltratingCD4+Tcells.WorldJ.Surg.19,352–358(1995).CAS  PubMed  GoogleScholar  Fife,B.T.&Bluestone,J.A.ControlofperipheralT-celltoleranceandautoimmunityviatheCTLA-4andPD-1pathways.Immunol.Rev.224,166–182(2008).CAS  PubMed  GoogleScholar  Brunet,J.F.etal.Anewmemberoftheimmunoglobulinsuperfamily—CTLA-4.Nature328,267–270(1987).ThisstudyscreensmouseTcellcDNAlibrariesandidentifiesCTLA4asanewimmunoglobulinsuperfamilymemberexpressedwithinthelymphoidlineagepredominantlyinactivatedcells.CAS  PubMed  GoogleScholar  Dariavach,P.,Mattei,M.G.,Golstein,P.&Lefranc,M.P.HumanIgsuperfamilyCTLA-4gene:chromosomallocalizationandidentityofproteinsequencebetweenmurineandhumanCTLA-4cytoplasmicdomains.Eur.J.Immunol.18,1901–1905(1988).CAS  PubMed  GoogleScholar  Harper,K.etal.CTLA-4andCD28activatedlymphocytemoleculesarecloselyrelatedinbothmouseandhumanastosequence,messageexpression,genestructure,andchromosomallocation.J.Immunol.147,1037–1044(1991).CAS  PubMed  GoogleScholar  Walunas,T.L.etal.CTLA-4canfunctionasanegativeregulatorofTcellactivation.Immunity1,405–413(1994).CAS  PubMed  GoogleScholar  Lo,B.etal.AUTOIMMUNEDISEASE.PatientswithLRBAdeficiencyshowCTLA4lossandimmunedysregulationresponsivetoabatacepttherapy.Science349,436–440(2015).CAS  PubMed  GoogleScholar  Linsley,P.S.etal.CTLA-4isasecondreceptorfortheBcellactivationantigenB7.J.Exp.Med.174,561–569(1991).CAS  PubMed  GoogleScholar  Linsley,P.S.etal.HumanB7-1(CD80)andB7-2(CD86)bindwithsimilaraviditiesbutdistinctkineticstoCD28andCTLA-4receptors.Immunity1,793–801(1994).ThisstudydemonstratesthatCD80andCD86bindtoCTLA4withgreateraviditythanCD28.CAS  PubMed  GoogleScholar  Pentcheva-Hoang,T.,Egen,J.G.,Wojnoonski,K.&Allison,J.P.B7-1andB7-2selectivelyrecruitCTLA-4andCD28totheimmunologicalsynapse.Immunity21,401–413(2004).CAS  PubMed  GoogleScholar  Krummel,M.F.&Allison,J.P.CD28andCTLA-4haveopposingeffectsontheresponseofTcellstostimulation.J.Exp.Med.182,459–465(1995).CAS  PubMed  GoogleScholar  Krummel,M.F.&Allison,J.P.CTLA-4engagementinhibitsIL-2accumulationandcellcycleprogressionuponactivationofrestingTcells.J.Exp.Med.183,2533–2540(1996).CAS  PubMed  GoogleScholar  Waterhouse,P.etal.LymphoproliferativedisorderswithearlylethalityinmicedeficientinCtla-4.Science270,985–988(1995).CAS  PubMed  GoogleScholar  Tivol,E.A.etal.CTLA4IgpreventslymphoproliferationandfatalmultiorgantissuedestructioninCTLA-4-deficientmice.J.Immunol.158,5091–5094(1997).AlongwithWaterhouseetal.(1995),thisinvivomurinestudydemonstratesthatCD4+TcellsarenecessarytocauseseveremultiorganautoimmunityinthecontextofCTLA4deficiency,whichcouldbereversedbyCTLA4Ig.CAS  PubMed  GoogleScholar  Mandelbrot,D.A.,McAdam,A.J.&Sharpe,A.H.B7-1orB7-2isrequiredtoproducethelymphoproliferativephenotypeinmicelackingcytotoxicTlymphocyte-associatedantigen4(CTLA-4).J.Exp.Med.189,435–440(1999).CAS  PubMed  PubMedCentral  GoogleScholar  Tai,X.,VanLaethem,F.,Sharpe,A.H.&Singer,A.InductionofautoimmunediseaseinCTLA-4–/–micedependsonaspecificCD28motifthatisrequiredforinvivocostimulation.Proc.NatlAcad.Sci.USA104,13756–13761(2007).CAS  PubMed  PubMedCentral  GoogleScholar  Lee,S.etal.AbataceptalleviatessevereautoimmunesymptomsinapatientcarryingadenovovariantinCTLA-4.J.AllergyClin.Immunol.137,327–330(2016).PubMed  GoogleScholar  Kuehn,H.S.etal.ImmunedysregulationinhumansubjectswithheterozygousgermlinemutationsinCTLA4.Science345,1623–1627(2014).CAS  PubMed  PubMedCentral  GoogleScholar  Intlekofer,A.M.&Thompson,C.B.Atthebench:preclinicalrationaleforCTLA-4andPD-1blockadeascancerimmunotherapy.J.Leukoc.Biol.94,25–39(2013).CAS  PubMed  PubMedCentral  GoogleScholar  Darlington,P.J.etal.SurfacecytotoxicTlymphocyte–associatedantigen4partitionswithinlipidraftsandrelocatestotheimmunologicalsynapseunderconditionsofinhibitionofTcellactivation.J.Exp.Med.195,1337(2002).ThisstudyprovideskeyinsightsintothecompartmentalizationofCTLA4throughouttheTcellactivationcycle.CAS  PubMed  PubMedCentral  GoogleScholar  Schneider,H.etal.ReversaloftheTCRstopsignalbyCTLA-4.Science313,1972–1975(2006).CAS  PubMed  GoogleScholar  Qureshi,O.S.etal.Trans-endocytosisofCD80andCD86:amolecularbasisforthecell-extrinsicfunctionofCTLA-4.Science332,600–603(2011).Thisstudynominatestrans-endocytosisofCD80andCD86asacell-extrinsicmechanismofCTLA4-mediatedinhibitionofTcellactivation.CAS  PubMed  PubMedCentral  GoogleScholar  Greenwald,R.J.,Boussiotis,V.A.,Lorsbach,R.B.,Abbas,A.K.&Sharpe,A.H.CTLA-4regulatesinductionofanergyinvivo.Immunity14,145–155(2001).UsingTCRtransgenicmice,thisstudyprovidesimportantinvivoevidencethatCTLA4isessentialforTcelltolerancebyregulatingentranceintotheanergicstate.CAS  PubMed  GoogleScholar  Chuang,E.etal.RegulationofcytotoxicTlymphocyte-associatedmolecule-4bySrckinases.J.Immunol.162,1270–1277(1999).CAS  PubMed  GoogleScholar  Marengere,L.E.etal.RegulationofTcellreceptorsignalingbytyrosinephosphataseSYPassociationwithCTLA-4.Science272,1170–1173(1996).CAS  PubMed  GoogleScholar  Chuang,E.etal.TheCD28andCTLA-4receptorsassociatewiththeserine/threoninephosphatasePP2A.Immunity13,313–322(2000).CAS  PubMed  GoogleScholar  Fraser,J.H.,Rincon,M.,McCoy,K.D.&LeGros,G.CTLA4ligationattenuatesAP-1,NFATandNF-κBactivityinactivatedTcells.Eur.J.Immunol.29,838–844(1999).CAS  PubMed  GoogleScholar  Jain,N.,Nguyen,H.,Chambers,C.&Kang,J.DualfunctionofCTLA-4inregulatoryTcellsandconventionalTcellstopreventmultiorganautoimmunity.Proc.NatlAcad.Sci.USA107,1524–1528(2010).CAS  PubMed  PubMedCentral  GoogleScholar  Wing,K.etal.CTLA-4controloverFoxp3+regulatoryTcellfunction.Science322,271–275(2008).CAS  PubMed  GoogleScholar  Takahashi,T.etal.Immunologicself-tolerancemaintainedbyCD25+CD4+regulatoryTcellsconstitutivelyexpressingcytotoxicTlymphocyte-associatedantigen4.J.Exp.Med.192,303–310(2000).CAS  PubMed  PubMedCentral  GoogleScholar  Tai,X.etal.BasisofCTLA-4functioninregulatoryandconventionalCD4+Tcells.Blood119,5155–5163(2012).ThisstudydemonstratesthatCTLA4expressionwithinregulatoryTcellsisessentialforthecharacteristicsuppressivefunctionsofthesecellsontheimmuneresponse.CAS  PubMed  PubMedCentral  GoogleScholar  Walker,L.S.K.TregandCTLA-4:twointertwiningpathwaystoimmunetolerance.J.Autoimmunity45,49–57(2013).CAS  GoogleScholar  Chikuma,S.&Bluestone,J.A.ExpressionofCTLA-4andFOXP3incisprotectsfromlethallymphoproliferativedisease.Eur.J.Immunol.37,1285–1289(2007).CAS  PubMed  GoogleScholar  Read,S.etal.BlockadeofCTLA-4onCD4+CD25+regulatoryTcellsabrogatestheirfunctioninvivo.J.Immunol.177,4376–4383(2006).CAS  PubMed  GoogleScholar  Read,S.,Malmström,V.&Powrie,F.CytotoxicTlymphocyte-associatedantigen4playsanessentialroleinthefunctionofCD25+CD4+regulatorycellsthatcontrolintestinalinflammation.J.Exp.Med.192,295–302(2000).CAS  PubMed  PubMedCentral  GoogleScholar  Friedline,R.H.etal.CD4+regulatoryTcellsrequireCTLA-4forthemaintenanceofsystemictolerance.J.Exp.Med.206,421–434(2009).CAS  PubMed  PubMedCentral  GoogleScholar  Sojka,D.K.,Hughson,A.&Fowell,D.J.CTLA-4isrequiredbyCD4+CD25+TregtocontrolCD4+T-celllymphopenia-inducedproliferation.Eur.J.Immunol.39,1544–1551(2009).CAS  PubMed  PubMedCentral  GoogleScholar  Hou,T.Z.etal.AtransendocytosismodelofCTLA-4functionpredictsitssuppressivebehavioronregulatoryTcells.J.Immunol.194,2148–2159(2015).CAS  PubMed  GoogleScholar  Grosso,J.F.&Jure-Kunkel,M.N.CTLA-4blockadeintumormodels:anoverviewofpreclinicalandtranslationalresearch.CancerImmun.13,5(2013).PubMed  PubMedCentral  GoogleScholar  Leach,D.R.,Krummel,M.F.&Allison,J.P.EnhancementofantitumorimmunitybyCTLA-4blockade.Science271,1734–1736(1996).ThisstudyelegantlyshowsthatCTLA4blockadeinvivocanenhanceimmune-mediatedantitumouralresponsesinmultipletumourmodelsthatultimatelypersistuponrechallenge.CAS  PubMed  GoogleScholar  Kwon,E.D.etal.ManipulationofTcellcostimulatoryandinhibitorysignalsforimmunotherapyofprostatecancer.Proc.NatlAcad.Sci.USA94,8099–8103(1997).CAS  PubMed  PubMedCentral  GoogleScholar  Fecci,P.E.etal.SystemicCTLA-4blockadeamelioratesglioma-inducedchangestotheCD4+TcellcompartmentwithoutaffectingregulatoryT-cellfunction.Clin.CancerRes.13,2158–2167(2007).CAS  PubMed  GoogleScholar  Yang,Y.F.etal.EnhancedinductionofantitumorT-cellresponsesbycytotoxicTlymphocyte-associatedmolecule-4blockade:theeffectismanifestedonlyattherestrictedtumor-bearingstages.CancerRes.57,4036–4041(1997).CAS  PubMed  GoogleScholar  Mangsbo,S.M.etal.EnhancedtumoreradicationbycombiningCTLA-4orPD-1blockadewithCpGtherapy.J.Immunother.33,225–235(2010).CAS  PubMed  GoogleScholar  Hurwitz,A.A.,Yu,T.F.Y.,Leach,D.R.&Allison,J.P.CTLA-4blockadesynergizeswithtumor-derivedgranulocyte–macrophagecolony-stimulatingfactorfortreatmentofanexperimentalmammarycarcinoma.Proc.NatlAcad.Sci.95,10067(1998).CAS  PubMed  PubMedCentral  GoogleScholar  vanElsas,A.,Hurwitz,A.A.&Allison,J.P.CombinationimmunotherapyofB16melanomausinganti-cytotoxicTlymphocyte-associatedantigen4(CTLA-4)andgranulocyte/macrophagecolony-stimulatingfactor(GM-CSF)-producingvaccinesinducesrejectionofsubcutaneousandmetastatictumorsaccompaniedbyautoimmunedepigmentation.J.Exp.Med.190,355–366(1999).PubMed  PubMedCentral  GoogleScholar  Jure-Kunkel,M.N.,Masters,G.,Girit,E.,Dito,G.&Lee,F.Y.Antitumoractivityofanti-CTLA-4monoclonalantibody(mAb)incombinationwithixabepiloneinpreclinicaltumormodels.J.Clin.Oncol.26,3048–3048(2008). GoogleScholar  Hodi,F.S.etal.BiologicactivityofcytotoxicTlymphocyte-associatedantigen4antibodyblockadeinpreviouslyvaccinatedmetastaticmelanomaandovariancarcinomapatients.Proc.NatlAcad.Sci.USA100,4712–4717(2003).CAS  PubMed  PubMedCentral  GoogleScholar  Hodi,F.S.etal.Improvedsurvivalwithipilimumabinpatientswithmetastaticmelanoma.N.Engl.J.Med.363,711–723(2010).CAS  PubMed  PubMedCentral  GoogleScholar  Schadendorf,D.etal.Pooledanalysisoflong-termsurvivaldatafromphaseIIandphaseIIItrialsofipilimumabinunresectableormetastaticmelanoma.J.Clin.Oncol.33,1889–1894(2015).Thisseminalmeta-analysisprovidesstrongclinicalevidencethatipilimumabconfersadurablesurvivalbenefittopatientswithadvancedmelanoma.CAS  PubMed  PubMedCentral  GoogleScholar  Maio,M.etal.Five-yearsurvivalratesfortreatment-naivepatientswithadvancedmelanomawhoreceivedipilimumabplusdacarbazineinaphaseIIItrial.J.Clin.Oncol.33,1191–1196(2015).CAS  PubMed  PubMedCentral  GoogleScholar  Yang,J.C.etal.Ipilimumab(anti-CTLA4antibody)causesregressionofmetastaticrenalcellcancerassociatedwithenteritisandhypophysitis.J.Immunother.30,825–830(2007).CAS  PubMed  PubMedCentral  GoogleScholar  Lynch,T.J.etal.Ipilimumabincombinationwithpaclitaxelandcarboplatinasfirst-linetreatmentinstageIIIB/IVnon-small-celllungcancer:resultsfromarandomized,double-blind,multicenterphaseIIstudy.J.Clin.Oncol.30,2046–2054(2012).CAS  PubMed  GoogleScholar  Reck,M.etal.Ipilimumabincombinationwithpaclitaxelandcarboplatinasfirst-linetherapyinextensive-disease-small-celllungcancer:resultsfromarandomized,double-blind,multicenterphase2trial.Ann.Oncol.24,75–83(2013).CAS  PubMed  GoogleScholar  Kwon,E.D.etal.Ipilimumabversusplaceboafterradiotherapyinpatientswithmetastaticcastration-resistantprostatecancerthathadprogressedafterdocetaxelchemotherapy(CA184-043):amulticentre,randomised,double-blind,phase3trial.LancetOncol.15,700–712(2014).CAS  PubMed  PubMedCentral  GoogleScholar  Ribas,A.etal.PhaseIIIrandomizedclinicaltrialcomparingtremelimumabwithstandard-of-carechemotherapyinpatientswithadvancedmelanoma.J.Clin.Oncol.31,616–622(2013).CAS  PubMed  PubMedCentral  GoogleScholar  Furness,A.J.,Vargas,F.A.,Peggs,K.S.&Quezada,S.A.ImpactoftumourmicroenvironmentandFcreceptorsontheactivityofimmunomodulatoryantibodies.TrendsImmunol.35,290–298(2014).CAS  PubMed  GoogleScholar  He,M.etal.RemarkablysimilarCTLA-4bindingpropertiesoftherapeuticipilimumabandtremelimumabantibodies.Oncotarget8,67129–67139(2017).PubMed  PubMedCentral  GoogleScholar  Baksh,K.&Weber,J.Immunecheckpointproteininhibitionforcancer:preclinicaljustificationforCTLA-4andPD-1blockadeandnewcombinations.Semin.Oncol.42,363–377(2015).CAS  PubMed  GoogleScholar  Snyder,A.etal.GeneticbasisforclinicalresponsetoCTLA-4blockadeinmelanoma.N.Engl.J.Med.371,2189–2199(2014).PubMed  PubMedCentral  GoogleScholar  vanRooij,N.etal.Tumorexomeanalysisrevealsneoantigen-specificT-cellreactivityinanipilimumab-responsivemelanoma.J.Clin.Oncol.31,e439–e442(2013).PubMed  GoogleScholar  Sharma,N.,Vacher,J.&Allison,J.P.TLR1/2ligandenhancesantitumorefficacyofCTLA-4blockadebyincreasingintratumoralTregdepletion.Proc.NatlAcad.Sci.USA116,10453(2019).CAS  PubMed  PubMedCentral  GoogleScholar  Peggs,K.S.,Quezada,S.A.,Chambers,C.A.,Korman,A.J.&Allison,J.P.BlockadeofCTLA-4onbotheffectorandregulatoryTcellcompartmentscontributestotheantitumoractivityofanti-CTLA-4antibodies.J.Exp.Med.206,1717–1725(2009).CAS  PubMed  PubMedCentral  GoogleScholar  Ha,D.etal.DifferentialcontrolofhumanTregandeffectorTcellsintumorimmunitybyFc-engineeredanti-CTLA-4antibody.Proc.NatlAcad.Sci.USA116,609(2019).CAS  PubMed  GoogleScholar  Sharma,A.etal.Anti-CTLA-4immunotherapydoesnotdepleteFOXP3+regulatoryTcells(Tregs)inhumancancers.Clin.CancerRes.25,1233(2019).CAS  PubMed  GoogleScholar  Ishida,Y.,Agata,Y.,Shibahara,K.&Honjo,T.InducedexpressionofPD-1,anovelmemberoftheimmunoglobulingenesuperfamily,uponprogrammedcelldeath.EMBOJ.11,3887–3895(1992).Usingsubtractivehybridization,thisstudyisthefirsttoidentifyPD1asanewimmunoglobulinsuperfamilymemberexpressedwithinthethymus.CAS  PubMed  PubMedCentral  GoogleScholar  Carreno,B.M.&Collins,M.TheB7familyofligandsanditsreceptors:newpathwaysforcostimulationandinhibitionofimmuneresponses.Annu.Rev.Immunol.20,29–53(2002).CAS  PubMed  GoogleScholar  Latchman,Y.etal.PD-L2isasecondligandforPD-1andinhibitsTcellactivation.Nat.Immunol.2,261–268(2001).CAS  PubMed  GoogleScholar  Francisco,L.M.,Sage,P.T.&Sharpe,A.H.ThePD-1pathwayintoleranceandautoimmunity.Immunol.Rev.236,219–242(2010).CAS  PubMed  PubMedCentral  GoogleScholar  Freeman,G.J.etal.EngagementofthePD-1immunoinhibitoryreceptorbyanovelB7familymemberleadstonegativeregulationoflymphocyteactivation.J.Exp.Med.192,1027–1034(2000).ThisstudydemonstratesthatanewB7familymember,PDL1,functionsasaligandforPD1inordertodampenTcellactivation.CAS  PubMed  PubMedCentral  GoogleScholar  Nishimura,H.,Minato,N.,Nakano,T.&Honjo,T.ImmunologicalstudiesonPD-1deficientmice:implicationofPD-1asanegativeregulatorforBcellresponses.Int.Immunol.10,1563–1572(1998).CAS  PubMed  GoogleScholar  Nishimura,H.,Nose,M.,Hiai,H.,Minato,N.&Honjo,T.Developmentoflupus-likeautoimmunediseasesbydisruptionofthePD-1geneencodinganITIMmotif-carryingimmunoreceptor.Immunity11,141–151(1999).CAS  PubMed  GoogleScholar  Nishimura,H.etal.AutoimmunedilatedcardiomyopathyinPD-1receptor-deficientmice.Science291,319–322(2001).CAS  PubMed  GoogleScholar  Wang,J.etal.EstablishmentofNOD-Pdcd1–/–miceasanefficientanimalmodeloftypeIdiabetes.Proc.NatlAcad.Sci.USA102,11823–11828(2005).CAS  PubMed  PubMedCentral  GoogleScholar  Keir,M.E.,Butte,M.J.,Freeman,G.J.&Sharpe,A.H.PD-1anditsligandsintoleranceandimmunity.Annu.Rev.Immunol.26,677–704(2008).CAS  PubMed  GoogleScholar  Hui,E.etal.TcellcostimulatoryreceptorCD28isaprimarytargetforPD-1-mediatedinhibition.Science355,1428–1433(2017).ThisstudyhighlightsthecentralroleofCD28dephosphorylationinmediatingthenegativeregulatoryeffectofPD1-mediatedTcellinhibition.CAS  PubMed  PubMedCentral  GoogleScholar  Parry,R.V.etal.CTLA-4andPD-1receptorsinhibitT-cellactivationbydistinctmechanisms.Mol.CellBiol.25,9543–9553(2005).ThisstudydemonstratesthecomplementarywaysinwhichCTLA4andPD1inhibitproteinkinaseBsignallingtoreduceglucoseuptakeandutilization.CAS  PubMed  PubMedCentral  GoogleScholar  Wei,S.C.etal.Distinctcellularmechanismsunderlieanti-CTLA-4andanti-PD-1checkpointblockade.Cell170,1120–1133.e17(2017).CAS  PubMed  PubMedCentral  GoogleScholar  Barber,D.L.etal.RestoringfunctioninexhaustedCD8Tcellsduringchronicviralinfection.Nature439,682–687(2006).CAS  PubMed  GoogleScholar  Blank,C.etal.PD-L1/B7H-1inhibitstheeffectorphaseoftumorrejectionbyTcellreceptor(TCR)transgenicCD8+Tcells.CancerRes.64,1140–1145(2004).CAS  PubMed  GoogleScholar  Francisco,L.M.etal.PD-L1regulatesthedevelopment,maintenance,andfunctionofinducedregulatoryTcells.J.Exp.Med.206,3015–3029(2009).CAS  PubMed  PubMedCentral  GoogleScholar  Wherry,E.J.&Kurachi,M.MolecularandcellularinsightsintoTcellexhaustion.Nat.Rev.Immunol.15,486–499(2015).CAS  PubMed  PubMedCentral  GoogleScholar  Hirano,F.etal.BlockadeofB7-H1andPD-1bymonoclonalantibodiespotentiatescancertherapeuticimmunity.CancerRes.65,1089–1096(2005).ThispreclinicalmurinestudyshowsthatblockadeofPD1orPDL1couldreverseinherentresistanceoftumourstocytolysisbyTcells.CAS  PubMed  GoogleScholar  Iwai,Y.etal.InvolvementofPD-L1ontumorcellsintheescapefromhostimmunesystemandtumorimmunotherapybyPD-L1blockade.Proc.NatlAcad.Sci.USA99,12293–12297(2002).ThisstudyshowsthatPDL1expressionbytumourcellsrepresentsamechanismofresistancetoimmune-mediatedcytolysisthatcanbeabrogatedbyblockadeofthePD1axis.CAS  PubMed  PubMedCentral  GoogleScholar  Strome,S.E.etal.B7-H1blockadeaugmentsadoptiveT-cellimmunotherapyforsquamouscellcarcinoma.CancerRes.63,6501–6505(2003).CAS  PubMed  GoogleScholar  He,Y.F.etal.Blockingprogrammeddeath-1ligand–PD-1interactionsbylocalgenetherapyresultsinenhancementofantitumoreffectofsecondarylymphoidtissuechemokine.J.Immunol.173,4919–4928(2004).CAS  PubMed  GoogleScholar  Kamphorst,A.O.etal.RescueofexhaustedCD8TcellsbyPD-1-targetedtherapiesisCD28-dependent.Science355,1423–1427(2017).CAS  PubMed  PubMedCentral  GoogleScholar  Iwai,Y.,Terawaki,S.&Honjo,T.PD-1blockadeinhibitshematogenousspreadofpoorlyimmunogenictumorcellsbyenhancedrecruitmentofeffectorTcells.Int.Immunol.17,133–144(2005).Beyondenhancingantitumouralimmunity,thisstudydemonstratesthatPD1blockadecanlimittumourmetastaticpotential.CAS  PubMed  GoogleScholar  Hamanishi,J.etal.Programmedcelldeath1ligand1andtumor-infiltratingCD8+Tlymphocytesareprognosticfactorsofhumanovariancancer.Proc.NatlAcad.Sci.USA104,3360–3365(2007).CAS  PubMed  PubMedCentral  GoogleScholar  Thompson,R.H.etal.PD-1isexpressedbytumor-infiltratingimmunecellsandisassociatedwithpooroutcomeforpatientswithrenalcellcarcinoma.Clin.CancerRes.13,1757–1761(2007).CAS  PubMed  GoogleScholar  Thompson,R.H.etal.TumorB7-H1isassociatedwithpoorprognosisinrenalcellcarcinomapatientswithlong-termfollow-up.CancerRes.66,3381–3385(2006).AlongwithThompsonetal.(2007)andHamanishietal.(2007),thisstudyshowsthatexpressionofPD1ontumour-infiltratingTcellsandPD1ligandsontumoursarepoorprognosticmarkersinvariouscancers.CAS  PubMed  GoogleScholar  Hargadon,K.M.,Johnson,C.E.&Williams,C.J.Immunecheckpointblockadetherapyforcancer:anoverviewofFDA-approvedimmunecheckpointinhibitors.Int.Immunopharmacol.62,29–39(2018).CAS  PubMed  GoogleScholar  Berman,D.etal.Thedevelopmentofimmunomodulatorymonoclonalantibodiesasanewtherapeuticmodalityforcancer:theBristol-MyersSquibbexperience.Pharmacol.Ther.148,132–153(2015).CAS  PubMed  GoogleScholar  Brahmer,J.R.etal.PhaseIstudyofsingle-agentanti-programmeddeath-1(MDX-1106)inrefractorysolidtumors:safety,clinicalactivity,pharmacodynamics,andimmunologiccorrelates.J.Clin.Oncol.28,3167–3175(2010).CAS  PubMed  PubMedCentral  GoogleScholar  Gong,J.,Chehrazi-Raffle,A.,Reddi,S.&Salgia,R.DevelopmentofPD-1andPD-L1inhibitorsasaformofcancerimmunotherapy:acomprehensivereviewofregistrationtrialsandfutureconsiderations.J.Immunother.Cancer6,8(2018).PubMed  PubMedCentral  GoogleScholar  Weber,J.S.etal.Nivolumabversuschemotherapyinpatientswithadvancedmelanomawhoprogressedafteranti-CTLA-4treatment(CheckMate037):arandomised,controlled,open-label,phase3trial.LancetOncol.16,375–384(2015).CAS  PubMed  GoogleScholar  Weber,J.etal.AdjuvantnivolumabversusipilimumabinresectedstageIIIorIVmelanoma.N.Engl.J.Med.377,1824–1835(2017).CAS  PubMed  GoogleScholar  Robert,C.etal.NivolumabinpreviouslyuntreatedmelanomawithoutBRAFmutation.N.Engl.J.Med.372,320–330(2015).CAS  PubMed  GoogleScholar  Robert,C.etal.Pembrolizumabversusipilimumabinadvancedmelanoma.N.Engl.J.Med.372,2521–2532(2015).ThisphaseIIIclinicalstudyinadvancedmelanomapatientsshowsthatPD1blockadewasmoreefficaciousandresultedinlesstoxicitythananti-CTLA4therapy.CAS  PubMed  GoogleScholar  Schachter,J.etal.Pembrolizumabversusipilimumabforadvancedmelanoma:finaloverallsurvivalresultsofamulticentre,randomised,open-labelphase3study(KEYNOTE-006).Lancet390,1853–1862(2017).CAS  PubMed  GoogleScholar  Herbst,R.S.etal.Pembrolizumabversusdocetaxelforpreviouslytreated,PD-L1-positive,advancednon-small-celllungcancer(KEYNOTE-010):arandomisedcontrolledtrial.Lancet387,1540–1550(2016).CAS  PubMed  GoogleScholar  Reck,M.etal.PembrolizumabversuschemotherapyforPD-L1-positivenon-small-celllungcancer.N.Engl.J.Med.375,1823–1833(2016).CAS  PubMed  GoogleScholar  Garon,E.B.etal.Pembrolizumabforthetreatmentofnon-small-celllungcancer.N.Engl.J.Med.372,2018–2028(2015).PubMed  GoogleScholar  Cohen,E.E.W.etal.Pembrolizumabversusmethotrexate,docetaxel,orcetuximabforrecurrentormetastatichead-and-necksquamouscellcarcinoma(KEYNOTE-040):arandomised,open-label,phase3study.Lancet393,156–167(2019).CAS  PubMed  GoogleScholar  Moskowitz,C.H.etal.Pembrolizumabinrelapsed/refractoryclassicalHodgkinlymphoma:primaryendpointanalysisofthephase2KEYNOTE-087study.Blood128,1107(2016). GoogleScholar  Bellmunt,J.etal.Pembrolizumabassecond-linetherapyforadvancedurothelialcarcinoma.N.Engl.J.Med.376,1015–1026(2017).CAS  PubMed  PubMedCentral  GoogleScholar  Fuchs,C.S.etal.Safetyandefficacyofpembrolizumabmonotherapyinpatientswithpreviouslytreatedadvancedgastricandgastroesophagealjunctioncancer:phase2clinicalKEYNOTE-059trial.JAMAOncol.4,e180013(2018).PubMed  PubMedCentral  GoogleScholar  Boyiadzis,M.M.etal.SignificanceandimplicationsofFDAapprovalofpembrolizumabforbiomarker-defineddisease.J.Immunother.Cancer6,35(2018).PubMed  PubMedCentral  GoogleScholar  Ding,L.&Chen,F.PredictingtumorresponsetoPD-1blockade.N.Engl.J.Med.381,477–479(2019).PubMed  GoogleScholar  Prasad,V.,Kaestner,V.&Mailankody,S.Cancerdrugsapprovedbasedonbiomarkersandnottumortype—FDAapprovalofpembrolizumabformismatchrepair-deficientsolidcancers.JAMAOncol.4,157–158(2018).PubMed  GoogleScholar  Motzer,R.J.etal.Nivolumabversuseverolimusinadvancedrenal-cellcarcinoma.N.Engl.J.Med.373,1803–1813(2015).CAS  PubMed  PubMedCentral  GoogleScholar  Ferris,R.L.etal.Nivolumabforrecurrentsquamous-cellcarcinomaoftheheadandneck.N.Engl.J.Med.375,1856–1867(2016).PubMed  PubMedCentral  GoogleScholar  Sharma,P.etal.Nivolumabinmetastaticurothelialcarcinomaafterplatinumtherapy(CheckMate275):amulticentre,single-arm,phase2trial.LancetOncol.18,312–322(2017).CAS  PubMed  GoogleScholar  El-Khoueiry,A.B.etal.Nivolumabinpatientswithadvancedhepatocellularcarcinoma(CheckMate040):anopen-label,non-comparative,phase1/2doseescalationandexpansiontrial.Lancet389,2492–2502(2017).CAS  PubMed  PubMedCentral  GoogleScholar  Ansell,S.M.etal.PD-1blockadewithnivolumabinrelapsedorrefractoryHodgkin’slymphoma.N.Engl.J.Med.372,311–319(2015).PubMed  GoogleScholar  Overman,M.J.etal.NivolumabinpatientswithmetastaticDNAmismatchrepair-deficientormicrosatelliteinstability-highcolorectalcancer(CheckMate142):anopen-label,multicentre,phase2study.LancetOncol.18,1182–1191(2017).CAS  PubMed  PubMedCentral  GoogleScholar  Topalian,S.L.etal.Five-yearsurvivalandcorrelatesamongpatientswithadvancedmelanoma,renalcellcarcinoma,ornon-smallcelllungcancertreatedwithnivolumab.JAMAOncol.5,1411–1420(2019).PubMedCentral  PubMed  GoogleScholar  Dong,H.etal.Tumor-associatedB7-H1promotesT-cellapoptosis:apotentialmechanismofimmuneevasion.Nat.Med.8,793–800(2002).CAS  PubMed  GoogleScholar  Rosenberg,J.E.etal.Atezolizumabinpatientswithlocallyadvancedandmetastaticurothelialcarcinomawhohaveprogressedfollowingtreatmentwithplatinum-basedchemotherapy:asingle-arm,multicentre,phase2trial.Lancet387,1909–1920(2016).CAS  PubMed  PubMedCentral  GoogleScholar  Powles,T.etal.Atezolizumabversuschemotherapyinpatientswithplatinum-treatedlocallyadvancedormetastaticurothelialcarcinoma(IMvigor211):amulticentre,open-label,phase3randomisedcontrolledtrial.Lancet391,748–757(2018).CAS  PubMed  GoogleScholar  Rittmeyer,A.etal.Atezolizumabversusdocetaxelinpatientswithpreviouslytreatednon-small-celllungcancer(OAK):aphase3,open-label,multicentrerandomisedcontrolledtrial.Lancet389,255–265(2017).PubMed  GoogleScholar  Schmid,P.etal.Atezolizumabandnab-paclitaxelinadvancedtriple-negativebreastcancer.N.Engl.J.Med.379,2108–2121(2018).CAS  PubMed  GoogleScholar  Horn,L.etal.First-lineatezolizumabpluschemotherapyinextensive-stagesmall-celllungcancer.N.Engl.J.Med.379,2220–2229(2018).CAS  PubMed  GoogleScholar  Kaufman,H.L.etal.Avelumabinpatientswithchemotherapy-refractorymetastaticMerkelcellcarcinoma:amulticentre,single-group,open-label,phase2trial.LancetOncol.17,1374–1385(2016).CAS  PubMed  PubMedCentral  GoogleScholar  Patel,M.R.etal.Avelumabinmetastaticurothelialcarcinomaafterplatinumfailure(JAVELINSolidTumor):pooledresultsfromtwoexpansioncohortsofanopen-label,phase1trial.LancetOncol.19,51–64(2018).CAS  PubMed  GoogleScholar  Motzer,R.J.etal.Avelumabplusaxitinibversussunitinibforadvancedrenal-cellcarcinoma.N.Engl.J.Med.380,1103–1115(2019).CAS  PubMed  PubMedCentral  GoogleScholar  Powles,T.etal.Efficacyandsafetyofdurvalumabinlocallyadvancedormetastaticurothelialcarcinoma:updatedresultsfromaphase1/2open-labelstudy.JAMAOncol.3,e172411(2017).PubMed  PubMedCentral  GoogleScholar  Antonia,S.J.etal.DurvalumabafterchemoradiotherapyinstageIIInon-small-celllungcancer.N.Engl.J.Med.377,1919–1929(2017).CAS  PubMed  GoogleScholar  Fritz,J.M.&Lenardo,M.J.Developmentofimmunecheckpointtherapyforcancer.J.Exp.Med.216,1244–1254(2019).CAS  PubMed  PubMedCentral  GoogleScholar  Michot,J.M.etal.Immune-relatedadverseeventswithimmunecheckpointblockade:acomprehensivereview.Eur.J.Cancer54,139–148(2016).CAS  PubMed  GoogleScholar  Kumar,V.etal.Currentdiagnosisandmanagementofimmunerelatedadverseevents(irAEs)inducedbyimmunecheckpointinhibitortherapy.Front.Pharmacol.8,49(2017).Thiscomprehensivereviewdescribesthediagnosisofthecommonimmune-relatedadverseeventsobservedinpatientstreatedwithimmunecheckpointinhibitorsandthesubsequentclinicalmanagementofthesesideeffects.CAS  PubMed  PubMedCentral  GoogleScholar  Postow,M.A.,Sidlow,R.&Hellmann,M.D.Immune-relatedadverseeventsassociatedwithimmunecheckpointblockade.N.Engl.J.Med.378,158–168(2018).CAS  PubMed  GoogleScholar  Wang,P.-F.etal.Immune-relatedadverseeventsassociatedwithanti-PD-1/PD-L1treatmentformalignancies:ameta-analysis.Front.Pharmacol.8,730(2017).PubMed  PubMedCentral  GoogleScholar  Champiat,S.etal.Hyperprogressivediseaseisanewpatternofprogressionincancerpatientstreatedbyanti-PD-1/PD-L1.Clin.CancerRes.23,1920–1928(2017).CAS  PubMed  GoogleScholar  Saada-Bouzid,E.etal.Hyperprogressionduringanti-PD-1/PD-L1therapyinpatientswithrecurrentand/ormetastaticheadandnecksquamouscellcarcinoma.Ann.Oncol.28,1605–1611(2017).CAS  PubMed  GoogleScholar  Ferrara,R.etal.Hyperprogressivediseaseinpatientswithadvancednon-smallcelllungcancertreatedwithPD-1/PD-L1inhibitorsorwithsingle-agentchemotherapy.JAMAOncol.4,1543–1552(2018).PubMed  PubMedCentral  GoogleScholar  Rauch,D.A.etal.RapidprogressionofadultT-cellleukemia/lymphomaastumor-infiltratingTregsafterPD-1blockade.Blood134,1406–1414(2019).PubMed  PubMedCentral  GoogleScholar  Tazdait,M.etal.PatternsofresponsesinmetastaticNSCLCduringPD-1orPDL-1inhibitortherapy:comparisonofRECIST1.1,irRECISTandiRECISTcriteria.Eur.J.Cancer88,38–47(2018).CAS  PubMed  GoogleScholar  Champiat,S.etal.Hyperprogressivedisease:recognizinganovelpatterntoimprovepatientmanagement.Nat.Rev.Clin.Oncol.15,748–762(2018).CAS  PubMed  GoogleScholar  Liu,J.,Blake,S.J.,Smyth,M.J.&Teng,M.W.ImprovedmousemodelstoassesstumourimmunityandirAEsaftercombinationcancerimmunotherapies.Clin.TranslImmunol.3,e22(2014). GoogleScholar  Du,X.etal.AreappraisalofCTLA-4checkpointblockadeincancerimmunotherapy.CellRes.28,416–432(2018).CAS  PubMed  PubMedCentral  GoogleScholar  Nishijima,T.F.,Shachar,S.S.,Nyrop,K.A.&Muss,H.B.SafetyandtolerabilityofPD-1/PD-L1inhibitorscomparedwithchemotherapyinpatientswithadvancedcancer:ameta-analysis.Oncologist22,470–479(2017).CAS  PubMed  PubMedCentral  GoogleScholar  Zhang,Y.etal.Hijackingantibody-inducedCTLA-4lysosomaldegradationforsaferandmoreeffectivecancerimmunotherapy.CellRes.29,609–627(2019).CAS  PubMed  PubMedCentral  GoogleScholar  Liu,Y.&Zheng,P.PreservingtheCTLA-4checkpointforsaferandmoreeffectivecancerimmunotherapy.TrendsPharmacol.Sci.41,4–12(2020).CAS  PubMed  GoogleScholar  Riley,R.S.,June,C.H.,Langer,R.&Mitchell,M.J.Deliverytechnologiesforcancerimmunotherapy.Nat.Rev.Drug.Discov.18,175–196(2019).CAS  PubMed  PubMedCentral  GoogleScholar  Friedman,C.F.,Proverbs-Singh,T.A.&Postow,M.A.Treatmentoftheimmune-relatedadverseeffectsofimmunecheckpointinhibitors:areview.JAMAOncol.2,1346–1353(2016).PubMed  GoogleScholar  Shahabi,V.etal.Geneexpressionprofilingofwholebloodinipilimumab-treatedpatientsforidentificationofpotentialbiomarkersofimmune-relatedgastrointestinaladverseevents.J.TranslMed.11,75(2013).CAS  PubMed  PubMedCentral  GoogleScholar  Callahan,M.K.etal.EvaluationofserumIL-17levelsduringipilimumabtherapy:correlationwithcolitis.J.Clin.Oncol.29,2505–2505(2011). GoogleScholar  Schindler,K.etal.Correlationofabsoluteandrelativeeosinophilcountswithimmune-relatedadverseeventsinmelanomapatientstreatedwithipilimumab.J.Clin.Oncol.32,9096(2014). GoogleScholar  Southam,C.M.,Brunschwig,A.,Levin,A.G.&Dizon,Q.S.Effectofleukocytesontransplantabilityofhumancancer.Cancer19,1743–1753(1966).Thisclinicalstudyisthefirsttodemonstratetheviabilityofusingpatient-derivedleukocytesandautologoustumourcellstopromotecancerregression.CAS  PubMed  GoogleScholar  Weiden,P.L.etal.Antileukemiceffectofgraft-versus-hostdiseaseinhumanrecipientsofallogeneic-marrowgrafts.N.Engl.J.Med.300,1068–1073(1979).CAS  PubMed  GoogleScholar  Rosenberg,S.A.etal.Useoftumor-infiltratinglymphocytesandinterleukin-2intheimmunotherapyofpatientswithmetastaticmelanoma.Apreliminaryreport.N.Engl.J.Med.319,1676–1680(1988).CAS  PubMed  GoogleScholar  Rosenberg,S.A.etal.Treatmentofpatientswithmetastaticmelanomawithautologoustumor-infiltratinglymphocytesandinterleukin2.J.NatlCancerInst.86,1159–1166(1994).CAS  PubMed  GoogleScholar  Rosenberg,S.A.etal.DurablecompleteresponsesinheavilypretreatedpatientswithmetastaticmelanomausingT-celltransferimmunotherapy.Clin.CancerRes.17,4550–4557(2011).ThisstudyexpandsontheclinicalsuccessofIL-2-expandedtumour-infiltratinglymphocytesincancertreatmentthroughtheadditionoflymphodepletionbeforeadministrationofthecellulartherapy.CAS  PubMed  PubMedCentral  GoogleScholar  Zacharakis,N.etal.Immunerecognitionofsomaticmutationsleadingtocompletedurableregressioninmetastaticbreastcancer.Nat.Med.24,724–730(2018).CAS  PubMed  PubMedCentral  GoogleScholar  Palmer,D.C.etal.CishactivelysilencesTCRsignalinginCD8+Tcellstomaintaintumortolerance.J.Exp.Med.212,2095(2015).CAS  PubMed  PubMedCentral  GoogleScholar  Perica,K.,Varela,J.C.,Oelke,M.&Schneck,J.AdoptiveTcellimmunotherapyforcancer.RambamMaimonidesMed.J.6,e0004(2015).PubMed  PubMedCentral  GoogleScholar  Garrido,F.,Aptsiauri,N.,Doorduijn,E.M.,GarciaLora,A.M.&vanHall,T.TheurgentneedtorecoverMHCclassIincancersforeffectiveimmunotherapy.Curr.Opin.Immunol.39,44–51(2016).CAS  PubMed  PubMedCentral  GoogleScholar  Kuwana,Y.etal.Expressionofchimericreceptorcomposedofimmunoglobulin-derivedVregionsandT-cellreceptor-derivedCregions.Biochem.Biophys.Res.Commun.149,960–968(1987).CAS  PubMed  GoogleScholar  Brocker,T.ChimericFv-ζorFv-εreceptorsarenotsufficienttoinduceactivationorcytokineproductioninperipheralTcells.Blood96,1999–2001(2000).CAS  PubMed  GoogleScholar  Jensen,M.C.etal.AntitransgenerejectionresponsescontributetoattenuatedpersistenceofadoptivelytransferredCD20/CD19-specificchimericantigenreceptorredirectedTcellsinhumans.Biol.BloodMarrowTranspl.16,1245–1256(2010).CAS  GoogleScholar  Maher,J.,Brentjens,R.J.,Gunset,G.,Riviere,I.&Sadelain,M.HumanT-lymphocytecytotoxicityandproliferationdirectedbyasinglechimericTCRζ/CD28receptor.Nat.Biotechnol.20,70–75(2002).ThispreclinicalstudyhighlightsanincreasedefficacyofCARTcellsthatincludesaco-stimulatorydomaincomparedwiththeCD3ζ-chainalone.CAS  PubMed  GoogleScholar  Kuhn,N.F.etal.CD40ligand-modifiedchimericantigenreceptorTcellsenhanceantitumorfunctionbyelicitinganendogenousantitumorresponse.CancerCell35,473–488.e6(2019).CAS  PubMed  PubMedCentral  GoogleScholar  Finney,H.M.,Akbar,A.N.&Lawson,A.D.ActivationofrestinghumanprimaryTcellswithchimericreceptors:costimulationfromCD28,induciblecostimulator,CD134,andCD137inserieswithsignalsfromtheTCRζchain.J.Immunol.172,104–113(2004).CAS  PubMed  GoogleScholar  Imai,C.etal.Chimericreceptorswith4-1BBsignalingcapacityprovokepotentcytotoxicityagainstacutelymphoblasticleukemia.Leukemia18,676–684(2004).CAS  PubMed  GoogleScholar  Rafiq,S.etal.TargeteddeliveryofaPD-1-blockingscFvbyCAR-Tcellsenhancesanti-tumorefficacyinvivo.Nat.Biotechnol.36,847–856(2018).CAS  PubMed  PubMedCentral  GoogleScholar  Eyquem,J.etal.TargetingaCARtotheTRAClocuswithCRISPR/Cas9enhancestumourrejection.Nature543,113–117(2017).CAS  PubMed  PubMedCentral  GoogleScholar  Porter,D.L.,Levine,B.L.,Kalos,M.,Bagg,A.&June,C.H.Chimericantigenreceptor-modifiedTcellsinchroniclymphoidleukemia.N.Engl.J.Med.365,725–733(2011).ThispilotclinicalstudydemonstratesthefeasibilityandpreliminaryefficacyofCD19-directedCARTcellsinchroniclymphocyticleukaemia.CAS  PubMed  PubMedCentral  GoogleScholar  Brentjens,R.J.etal.CD19-targetedTcellsrapidlyinducemolecularremissionsinadultswithchemotherapy-refractoryacutelymphoblasticleukemia.Sci.TranslMed.5,177ra138(2013).Beyondchroniclymphocyticleukaemia,thisclinicaltrialdemonstratesthatCD19-directedCARTcellscouldinduceremissionintheacuteformofthedisease.CAS  Article  GoogleScholar  Park,J.H.etal.Long-termfollow-upofCD19CARtherapyinacutelymphoblasticleukemia.N.Engl.J.Med.378,449–459(2018).CAS  PubMed  PubMedCentral  GoogleScholar  Neelapu,S.S.etal.AxicabtageneciloleucelCART-celltherapyinrefractorylargeB-celllymphoma.N.Engl.J.Med.377,2531–2544(2017).CAS  PubMed  PubMedCentral  GoogleScholar  Fry,T.J.etal.CD22-targetedCARTcellsinduceremissioninB-ALLthatisnaiveorresistanttoCD19-targetedCARimmunotherapy.Nat.Med.24,20–28(2018).CAS  PubMed  GoogleScholar  Jackson,H.J.,Rafiq,S.&Brentjens,R.J.DrivingCART-cellsforward.Nat.Rev.Clin.Oncol.13,370–383(2016).CAS  PubMed  PubMedCentral  GoogleScholar  Yamamoto,T.N.,Kishton,R.J.&Restifo,N.P.Developingneoantigen-targetedTcell-basedtreatmentsforsolidtumors.Nat.Med.25,1488–1499(2019).CAS  PubMed  GoogleScholar  Raje,N.etal.Anti-BCMACART-celltherapybb2121inrelapsedorrefractorymultiplemyeloma.N.Engl.J.Med.380,1726–1737(2019).CAS  PubMed  PubMedCentral  GoogleScholar  Cohen,A.D.etal.Bcellmaturationantigen-specificCARTcellsareclinicallyactiveinmultiplemyeloma.J.Clin.Invest.129,2210–2221(2019).PubMed  PubMedCentral  GoogleScholar  Smith,E.L.etal.GPRC5DisatargetfortheimmunotherapyofmultiplemyelomawithrationallydesignedCARTcells.Sci.TranslMed.11,eaau7746(2019).PubMed  PubMedCentral  GoogleScholar  Beatty,G.L.etal.Mesothelin-specificchimericantigenreceptormRNA-engineeredTcellsinduceanti-tumoractivityinsolidmalignancies.CancerImmunol.Res.2,112–120(2014).CAS  PubMed  GoogleScholar  Kershaw,M.H.etal.AphaseIstudyonadoptiveimmunotherapyusinggene-modifiedTcellsforovariancancer.Clin.CancerRes.12,6106–6115(2006).CAS  PubMed  PubMedCentral  GoogleScholar  Park,J.R.etal.Adoptivetransferofchimericantigenreceptorre-directedcytolyticTlymphocyteclonesinpatientswithneuroblastoma.Mol.Ther.15,825–833(2007).CAS  PubMed  GoogleScholar  Majzner,R.G.etal.CARTcellstargetingB7-H3,apan-cancerantigen,demonstratepotentpreclinicalactivityagainstpediatricsolidtumorsandbraintumors.Clin.CancerRes.25,2560–2574(2019).CAS  PubMed  PubMedCentral  GoogleScholar  Batchu,R.B.etal.Inhibitionofinterleukin-10inthetumormicroenvironmentcanrestoremesothelinchimericantigenreceptorTcellactivityinpancreaticcancerinvitro.Surgery163,627–632(2018).PubMed  GoogleScholar  Chang,Z.L.etal.RewiringT-cellresponsestosolublefactorswithchimericantigenreceptors.Nat.Chem.Biol.14,317–324(2018).CAS  PubMed  PubMedCentral  GoogleScholar  Zhao,J.,Zhao,J.&Perlman,S.DifferentialeffectsofIL-12onTregsandnon-TregTcells:rolesofIFN-γ,IL-2andIL-2R.PLoSOne7,e46241(2012).CAS  PubMed  PubMedCentral  GoogleScholar  Chmielewski,M.,Kopecky,C.,Hombach,A.A.&Abken,H.IL-12releasebyengineeredTcellsexpressingchimericantigenreceptorscaneffectivelymusteranantigen-independentmacrophageresponseontumorcellsthathaveshutdowntumorantigenexpression.CancerRes.71,5697–5706(2011).CAS  PubMed  GoogleScholar  Kerkar,S.P.etal.IL-12triggersaprogrammaticchangeindysfunctionalmyeloid-derivedcellswithinmousetumors.J.Clin.Invest.121,4746–4757(2011).CAS  PubMed  PubMedCentral  GoogleScholar  Koneru,M.,Purdon,T.J.,Spriggs,D.,Koneru,S.&Brentjens,R.J.IL-12secretingtumor-targetedchimericantigenreceptorTcellseradicateovariantumorsinvivo.Oncoimmunology4,e994446(2015).PubMed  PubMedCentral  GoogleScholar  Yeku,O.O.,Purdon,T.J.,Koneru,M.,Spriggs,D.&Brentjens,R.J.ArmoredCARTcellsenhanceantitumorefficacyandovercomethetumormicroenvironment.Sci.Rep.7,10541(2017).PubMed  PubMedCentral  GoogleScholar  Koneru,M.,O’Cearbhaill,R.,Pendharkar,S.,Spriggs,D.R.&Brentjens,R.J.AphaseIclinicaltrialofadoptiveTcelltherapyusingIL-12secretingMUC-16ectodirectedchimericantigenreceptorsforrecurrentovariancancer.J.TranslMed.13,102(2015).PubMed  PubMedCentral  GoogleScholar  Wilkie,S.etal.Selectiveexpansionofchimericantigenreceptor-targetedT-cellswithpotenteffectorfunctionusinginterleukin-4.J.Biol.Chem.285,25538–25544(2010).CAS  PubMed  PubMedCentral  GoogleScholar  vanSchalkwyk,M.C.etal.DesignofaphaseIclinicaltrialtoevaluateintratumoraldeliveryofErbB-targetedchimericantigenreceptorT-cellsinlocallyadvancedorrecurrentheadandneckcancer.Hum.GeneTher.Clin.Dev.24,134–142(2013).PubMed  GoogleScholar  Lynn,R.C.etal.c-JunoverexpressioninCARTcellsinducesexhaustionresistance.Nature576,293–300(2019).CAS  PubMed  PubMedCentral  GoogleScholar  Brudno,J.N.&Kochenderfer,J.N.ToxicitiesofchimericantigenreceptorTcells:recognitionandmanagement.Blood127,3321–3330(2016).ThisreviewdetailstheadverseeffectsassociatedwithCARTcelltherapyandtheirsubsequentclinicalmanagement.CAS  PubMed  PubMedCentral  GoogleScholar  Neelapu,S.S.etal.ChimericantigenreceptorT-celltherapy—assessmentandmanagementoftoxicities.Nat.Rev.Clin.Oncol.15,47–62(2018).CAS  PubMed  GoogleScholar  Shimabukuro-Vornhagen,A.etal.Cytokinereleasesyndrome.J.Immunother.Cancer6,56(2018).PubMed  PubMedCentral  GoogleScholar  Grupp,S.A.etal.Chimericantigenreceptor-modifiedTcellsforacutelymphoidleukemia.N.Engl.J.Med.368,1509–1518(2013).CAS  PubMed  PubMedCentral  GoogleScholar  Conley,M.E.etal.PrimaryBcellimmunodeficiencies:comparisonsandcontrasts.Annu.Rev.Immunol.27,199–227(2009).CAS  PubMed  GoogleScholar  Giavridis,T.etal.CARTcell-inducedcytokinereleasesyndromeismediatedbymacrophagesandabatedbyIL-1blockade.Nat.Med.24,731–738(2018).CAS  PubMed  PubMedCentral  GoogleScholar  Ghorashian,S.etal.EnhancedCARTcellexpansionandprolongedpersistenceinpediatricpatientswithALLtreatedwithalow-affinityCD19CAR.Nat.Med.25,1408–1414(2019).CAS  PubMed  GoogleScholar  Bielamowicz,K.etal.TrivalentCARTcellsovercomeinterpatientantigenicvariabilityinglioblastoma.NeuroOncol.20,506–518(2018).CAS  PubMed  GoogleScholar  Hung,C.F.etal.Developmentofanti-humanmesothelin-targetedchimericantigenreceptormessengerRNA-transfectedperipheralbloodlymphocytesforovariancancertherapy.Hum.GeneTher.29,614–625(2018).CAS  PubMed  PubMedCentral  GoogleScholar  Jones,B.S.,Lamb,L.S.,Goldman,F.&DiStasi,A.Improvingthesafetyofcelltherapyproductsbysuicidegenetransfer.Front.Pharmacol.5,254–254(2014).PubMed  PubMedCentral  GoogleScholar  Hernandez,I.,Prasad,V.&Gellad,W.F.TotalcostsofchimericantigenreceptorT-cellimmunotherapy.JAMAOncol.4,994–996(2018).PubMed  PubMedCentral  GoogleScholar  Moon,E.K.,Langer,C.J.&Albelda,S.M.Theeraofcheckpointblockadeinlungcancer:takingthebrakesofftheimmunesystem.Ann.Am.Thorac.Soc.14,1248–1260(2017).PubMed  GoogleScholar  Vormittag,P.,Gunn,R.,Ghorashian,S.&Veraitch,F.S.AguidetomanufacturingCARTcelltherapies.Curr.Opin.Biotechnol.53,164–181(2018).CAS  PubMed  GoogleScholar  Guo,C.etal.Therapeuticcancervaccines:past,present,andfuture.Adv.CancerRes.119,421–475(2013).CAS  PubMed  PubMedCentral  GoogleScholar  Morales,A.,Eidinger,D.&Bruce,A.W.IntracavitaryBacillusCalmette–Guerininthetreatmentofsuperficialbladdertumors.J.Urol.116,180–183(1976).CAS  PubMed  GoogleScholar  vanderBruggen,P.etal.AgeneencodinganantigenrecognizedbycytolyticTlymphocytesonahumanmelanoma.Science254,1643–1647(1991).ThisearlystudyidentifiesamelanomaneoantigenthatcouldelicitaspecificcytolyticTcellresponse.PubMed  GoogleScholar  Hanna,M.G.Jr.&Peters,L.C.ImmunotherapyofestablishedmicrometastaseswithBacillusCalmette–Guerintumorcellvaccine.CancerRes.38,204–209(1978).PubMed  GoogleScholar  Heicappell,R.,Schirrmacher,V.,vonHoegen,P.,Ahlert,T.&Appelhans,B.Preventionofmetastaticspreadbypostoperativeimmunotherapywithvirallymodifiedautologoustumorcells.I.Parametersforoptimaltherapeuticeffects.Int.J.Cancer37,569–577(1986).CAS  PubMed  GoogleScholar  Plaksin,D.etal.Effectiveanti-metastaticmelanomavaccinationwithtumorcellstransfectedwithMHCgenesand/orinfectedwithNewcastlediseasevirus(NDV).Int.J.Cancer59,796–801(1994).CAS  PubMed  GoogleScholar  Burke,S.etal.OncolyticNewcastlediseasevirusactivationoftheinnateimmuneresponseandprimingofantitumoradaptiveresponsesinvitro.CancerImmunol.Immunother.https://doi.org/10.1007/s00262-020-02495-x(2020).Curran,M.A.&Allison,J.P.Tumorvaccinesexpressingflt3ligandsynergizewithctla-4blockadetorejectpreimplantedtumors.CancerRes.69,7747–7755(2009).CAS  PubMed  PubMedCentral  GoogleScholar  Rizvi,N.A.etal.Cancerimmunology.MutationallandscapedeterminessensitivitytoPD-1blockadeinnon-smallcelllungcancer.Science348,124–128(2015).CAS  PubMed  PubMedCentral  GoogleScholar  Tran,E.etal.Immunogenicityofsomaticmutationsinhumangastrointestinalcancers.Science350,1387–1390(2015).CAS  PubMed  PubMedCentral  GoogleScholar  Castle,J.C.etal.Exploitingthemutanomefortumorvaccination.CancerRes.72,1081–1091(2012).Byusingnext-generationDNAsequencing,thisstudyidentifiessomaticmutationsthatcreatenovelimmunogenicepitopesthatcanbesuccessfullytargetedbytherapeuticvaccination.CAS  PubMed  GoogleScholar  Kreiter,S.etal.MutantMHCclassIIepitopesdrivetherapeuticimmuneresponsestocancer.Nature520,692–696(2015).CAS  PubMed  PubMedCentral  GoogleScholar  Duan,F.etal.Genomicandbioinformaticprofilingofmutationalneoepitopesrevealsnewrulestopredictanticancerimmunogenicity.J.Exp.Med.211,2231–2248(2014).PubMed  PubMedCentral  GoogleScholar  Gubin,M.M.etal.Checkpointblockadecancerimmunotherapytargetstumour-specificmutantantigens.Nature515,577–581(2014).CAS  PubMed  PubMedCentral  GoogleScholar  Matsushita,H.etal.CancerexomeanalysisrevealsaT-cell-dependentmechanismofcancerimmunoediting.Nature482,400–404(2012).CAS  PubMed  PubMedCentral  GoogleScholar  Yadav,M.etal.Predictingimmunogenictumourmutationsbycombiningmassspectrometryandexomesequencing.Nature515,572–576(2014).CAS  PubMed  GoogleScholar  Alspach,E.etal.MHC-IIneoantigensshapetumourimmunityandresponsetoimmunotherapy.Nature574,696–701(2019).CAS  PubMed  PubMedCentral  GoogleScholar  Sahin,U.&Tureci,O.Personalizedvaccinesforcancerimmunotherapy.Science359,1355–1360(2018).CAS  PubMed  GoogleScholar  Zhang,X.,Sharma,P.K.,PeterGoedegebuure,S.&Gillanders,W.E.Personalizedcancervaccines:targetingthecancermutanome.Vaccine35,1094–1100(2017).CAS  PubMed  GoogleScholar  Ott,P.A.etal.Animmunogenicpersonalneoantigenvaccineforpatientswithmelanoma.Nature547,217–221(2017).CAS  PubMed  PubMedCentral  GoogleScholar  Sahin,U.etal.PersonalizedRNAmutanomevaccinesmobilizepoly-specifictherapeuticimmunityagainstcancer.Nature547,222–226(2017).CAS  PubMed  GoogleScholar  Nielsen,M.,Lund,O.,Buus,S.&Lundegaard,C.MHCclassIIepitopepredictivealgorithms.Immunology130,319–328(2010).CAS  PubMed  PubMedCentral  GoogleScholar  Motzer,R.J.etal.Nivolumabplusipilimumabversussunitinibinadvancedrenal-cellcarcinoma.N.Engl.J.Med.378,1277–1290(2018).CAS  PubMed  PubMedCentral  GoogleScholar  Wolchok,J.D.etal.Overallsurvivalwithcombinednivolumabandipilimumabinadvancedmelanoma.N.Engl.J.Med.377,1345–1356(2017).Thislong-termanalysisofapreviousphaseIIIclinicaltrialdemonstratesthatnivolumabandipilimumabcombinationtherapyconferredincreasedsurvivalcomparedwithipilimumabalone.CAS  PubMed  PubMedCentral  GoogleScholar  Zhao,Y.etal.PD-L1:CD80cis-heterodimertriggerstheco-stimulatoryreceptorCD28whilerepressingtheinhibitoryPD-1andCTLA-4pathways.Immunity51,1059–1073.e9(2019).ThisstudyelegantlyimplicatesliganddimerizationinthecrosstalkbetweentheCD28,CTLA4andPD1pathways.CAS  PubMed  PubMedCentral  GoogleScholar  Butte,M.J.,Keir,M.E.,Phamduy,T.B.,Sharpe,A.H.&Freeman,G.J.Programmeddeath-1ligand1interactsspecificallywiththeB7-1costimulatorymoleculetoinhibitTcellresponses.Immunity27,111–122(2007).CAS  PubMed  PubMedCentral  GoogleScholar  Ngwa,W.etal.Usingimmunotherapytoboosttheabscopaleffect.Nat.Rev.Cancer18,313–322(2018).CAS  PubMed  PubMedCentral  GoogleScholar  Twyman-SaintVictor,C.etal.Radiationanddualcheckpointblockadeactivatenon-redundantimmunemechanismsincancer.Nature520,373–377(2015).CAS  PubMed  GoogleScholar  Postow,M.A.etal.Immunologiccorrelatesoftheabscopaleffectinapatientwithmelanoma.N.Engl.J.Med.366,925–931(2012).CAS  PubMed  PubMedCentral  GoogleScholar  Burugu,S.,Dancsok,A.R.&Nielsen,T.O.Emergingtargetsincancerimmunotherapy.Semin.CancerBiol.52,39–52(2018).CAS  PubMed  GoogleScholar  Donini,C.,D’Ambrosio,L.,Grignani,G.,Aglietta,M.&Sangiolo,D.Nextgenerationimmune-checkpointsforcancertherapy.J.Thorac.Dis.10,S1581–S1601(2018).PubMed  PubMedCentral  GoogleScholar  Marin-Acevedo,J.A.etal.Nextgenerationofimmunecheckpointtherapyincancer:newdevelopmentsandchallenges.J.Hematol.Oncol.11,39(2018).PubMed  PubMedCentral  GoogleScholar  He,Y.etal.Lymphocyte-activationgene-3,animportantimmunecheckpointincancer.CancerSci.107,1193–1197(2016).CAS  PubMed  PubMedCentral  GoogleScholar  Deng,W.W.etal.LAG-3conferspoorprognosisanditsblockadereshapesantitumorresponseinheadandnecksquamouscellcarcinoma.Oncoimmunology5,e1239005(2016).PubMed  PubMedCentral  GoogleScholar  Sharma,P.&Allison,J.P.Thefutureofimmunecheckpointtherapy.Science348,56–61(2015).CAS  PubMed  GoogleScholar  Brignone,C.etal.First-linechemoimmunotherapyinmetastaticbreastcarcinoma:combinationofpaclitaxelandIMP321(LAG-3Ig)enhancesimmuneresponsesandantitumoractivity.J.TranslMed.8,71(2010).PubMed  PubMedCentral  GoogleScholar  Wang,J.etal.Fibrinogen-likeprotein1isamajorimmuneinhibitoryligandofLAG-3.Cell176,334–347.e12(2019).CAS  PubMed  GoogleScholar  Zhu,C.etal.TheTim-3ligandgalectin-9negativelyregulatesThelpertype1immunity.Nat.Immunol.6,1245–1252(2005).CAS  PubMed  GoogleScholar  Anderson,A.C.,Joller,N.&Kuchroo,V.K.Lag-3,Tim-3,andTIGIT:co-inhibitoryreceptorswithspecializedfunctionsinimmuneregulation.Immunity44,989–1004(2016).CAS  PubMed  PubMedCentral  GoogleScholar  Liu,J.etal.Immune-checkpointproteinsVISTAandPD-1nonredundantlyregulatemurineT-cellresponses.Proc.NatlAcad.Sci.USA112,6682–6687(2015).CAS  PubMed  PubMedCentral  GoogleScholar  Gao,J.etal.VISTAisaninhibitoryimmunecheckpointthatisincreasedafteripilimumabtherapyinpatientswithprostatecancer.Nat.Med.23,551–555(2017).CAS  PubMed  PubMedCentral  GoogleScholar  Powderly,J.etal.InterimresultsofanongoingphaseI,doseescalationstudyofMGA271(Fc-optimizedhumanizedanti-B7-H3monoclonalantibody)inpatientswithrefractoryB7-H3-expressingneoplasmsorneoplasmswhosevasculatureexpressesB7-H3.J.Immunother.Cancer3,O8(2015).PubMedCentral  GoogleScholar  Kramer,K.etal.Compartmentalintrathecalradioimmunotherapy:resultsfortreatmentformetastaticCNSneuroblastoma.J.Neurooncol.97,409–418(2010).PubMed  GoogleScholar  Tolcher,A.W.etal.Phase1,first-in-human,openlabel,doseescalationctudyofMGD009,ahumanizedB7-H3×CD3dual-affinityre-targeting(DART)proteininpatientswithB7-H3-expressingneoplasmsorB7-H3expressingtumorvasculature.J.Clin.Oncol.34,TPS3105(2016). GoogleScholar  Chauvin,J.M.etal.TIGITandPD-1impairtumorantigen-specificCD8+Tcellsinmelanomapatients.J.Clin.Invest.125,2046–2058(2015).PubMed  PubMedCentral  GoogleScholar  Kowolik,C.M.etal.CD28costimulationprovidedthroughaCD19-specificchimericantigenreceptorenhancesinvivopersistenceandantitumorefficacyofadoptivelytransferredTcells.CancerRes.66,10995–11004(2006).CAS  PubMed  GoogleScholar  Coyle,A.J.etal.TheCD28-relatedmoleculeICOSisrequiredforeffectiveTcell-dependentimmuneresponses.Immunity13,95–105(2000).CAS  PubMed  GoogleScholar  Fan,X.,Quezada,S.A.,Sepulveda,M.A.,Sharma,P.&Allison,J.P.EngagementoftheICOSpathwaymarkedlyenhancesefficacyofCTLA-4blockadeincancerimmunotherapy.J.Exp.Med.211,715(2014).CAS  PubMed  PubMedCentral  GoogleScholar  Vonderheide,R.H.etal.Tremelimumabincombinationwithexemestaneinpatientswithadvancedbreastcancerandtreatment-associatedmodulationofinduciblecostimulatorexpressiononpatientTcells.Clin.CancerRes.16,3485–3494(2010).CAS  PubMed  GoogleScholar  Kjaergaard,J.etal.TherapeuticefficacyofOX-40receptorantibodydependsontumorimmunogenicityandanatomicsiteoftumorgrowth.CancerRes.60,5514–5521(2000).CAS  PubMed  GoogleScholar  Weinberg,A.D.etal.EngagementoftheOX-40receptorinvivoenhancesantitumorimmunity.J.Immunol.164,2160–2169(2000).CAS  PubMed  GoogleScholar  Valzasina,B.etal.TriggeringofOX40(CD134)onCD4+CD25+Tcellsblockstheirinhibitoryactivity:anovelregulatoryroleforOX40anditscomparisonwithGITR.Blood105,2845–2851(2005).CAS  PubMed  GoogleScholar  Parrott,D.M.V.,deSousa,M.A.B.&East,J.Thymus-dependentareasinthelymphoidorgansofneonatallythymectomizedmice.J.Exp.Med.123,191–204(1966).CAS  PubMed  PubMedCentral  GoogleScholar  Miller,J.F.&Mitchell,G.F.Celltocellinteractionintheimmuneresponse.I.Hemolysin-formingcellsinneonatallythymectomizedmicereconstitutedwiththymusorthoracicductlymphocytes.J.Exp.Med.128,801–820(1968).CAS  PubMed  PubMedCentral  GoogleScholar  LeBien,T.W.&Tedder,T.F.Blymphocytes:howtheydevelopandfunction.Blood112,1570–1580(2008).CAS  PubMed  PubMedCentral  GoogleScholar  vandenBroek,T.,Borghans,J.A.M.&vanWijk,F.ThefullspectrumofhumannaiveTcells.Nat.Rev.Immunol.18,363–373(2018).PubMed  GoogleScholar  Vignali,D.A.,Collison,L.W.&Workman,C.J.HowregulatoryTcellswork.Nat.Rev.Immunol.8,523–532(2008).CAS  PubMed  PubMedCentral  GoogleScholar  Kumar,B.V.,Connors,T.J.&Farber,D.L.HumanTcelldevelopment,localization,andfunctionthroughoutlife.Immunity48,202–213(2018).CAS  PubMed  PubMedCentral  GoogleScholar  Nikolich-Zugich,J.,Slifka,M.K.&Messaoudi,I.ThemanyimportantfacetsofT-cellrepertoirediversity.Nat.Rev.Immunol.4,123–132(2004).CAS  PubMed  GoogleScholar  Wilson,I.A.&Garcia,K.C.T-cellreceptorstructureandTCRcomplexes.Curr.Opin.Struct.Biol.7,839–848(1997).CAS  PubMed  GoogleScholar  Mueller,D.L.,Jenkins,M.K.&Schwartz,R.H.Clonalexpansionversusfunctionalclonalinactivation:acostimulatorysignallingpathwaydeterminestheoutcomeofTcellantigenreceptoroccupancy.Annu.Rev.Immunol.7,445–480(1989).CAS  PubMed  GoogleScholar  Martin,P.J.etal.A44kilodaltoncellsurfacehomodimerregulatesinterleukin2productionbyactivatedhumanTlymphocytes.J.Immunol.136,3282–3287(1986).CAS  PubMed  GoogleScholar  Gmunder,H.&Lesslauer,W.A45-kDahumanT-cellmembraneglycoproteinfunctionsintheregulationofcellproliferativeresponses.Eur.J.Biochem.142,153–160(1984).CAS  PubMed  GoogleScholar  June,C.H.,Ledbetter,J.A.,Linsley,P.S.&Thompson,C.B.RoleoftheCD28receptorinT-cellactivation.Immunol.Today11,211–216(1990).CAS  PubMed  GoogleScholar  Lesslauer,W.etal.T90/44(9.3antigen).AcellsurfacemoleculewithafunctioninhumanTcellactivation.Eur.J.Immunol.16,1289–1296(1986).CAS  PubMed  GoogleScholar  Hansen,J.A.,Martin,P.J.&Nowinski,R.C.MonoclonalantibodiesidentifyinganovelT-cellantigenandIaantigensofhumanlymphocytes.Immunogenetics10,247–260(1980).ThisstudyisthefirsttoidentifyanewTcellantigen,laternamedCD28,thatfunctionsinTcellco-stimulation. GoogleScholar  Hara,T.,Fu,S.M.&Hansen,J.A.HumanTcellactivation.II.AnewactivationpathwayusedbyamajorTcellpopulationviaadisulfide-bondeddimerofa44kilodaltonpolypeptide(9.3antigen).J.Exp.Med.161,1513–1524(1985)ThisstudyprovidesevidencethattherecentlydiscoveredCD28receptorfunctionedtoaugmentTcellactivation.CAS  PubMed  GoogleScholar  Jin,B.,Sun,T.,Yu,X.H.,Yang,Y.X.&Yeo,A.E.TheeffectsofTLRactivationonT-celldevelopmentanddifferentiation.Clin.Dev.Immunol.2012,836485(2012).PubMed  PubMedCentral  GoogleScholar  Sharpe,A.H.&Freeman,G.J.TheB7-CD28superfamily.Nat.Rev.Immunol.2,116–126(2002).CAS  PubMed  GoogleScholar  Buchbinder,E.I.&Desai,A.CTLA-4andPD-1pathways:similarities,differences,andimplicationsoftheirinhibition.Am.J.Clin.Oncol.39,98–106(2016).CAS  PubMed  PubMedCentral  GoogleScholar  Cantrell,D.A.T-cellantigenreceptorsignaltransduction.Immunology105,369–374(2002).CAS  PubMed  PubMedCentral  GoogleScholar  Palacios,E.H.&Weiss,A.FunctionoftheSrc-familykinases,LckandFyn,inT-celldevelopmentandactivation.Oncogene23,7990–8000(2004).CAS  PubMed  GoogleScholar  Alexander,D.R.TheCD45tyrosinephosphatase:apositiveandnegativeregulatorofimmunecellfunction.Semin.Immunol.12,349–359(2000).CAS  PubMed  GoogleScholar  Rossy,J.,Williamson,D.J.&Gaus,K.HowdoesthekinaseLckphosphorylatetheTcellreceptor?Spatialorganizationasaregulatorymechanism.Front.Immunol.3,167(2012).CAS  PubMed  PubMedCentral  GoogleScholar  Macian,F.etal.Transcriptionalmechanismsunderlyinglymphocytetolerance.Cell109,719–731(2002).CAS  PubMed  GoogleScholar  Miller,J.F.&Morahan,G.PeripheralTcelltolerance.Annu.Rev.Immunol.10,51–69(1992).CAS  PubMed  GoogleScholar  Lenardo,M.etal.MatureTlymphocyteapoptosis-immuneregulationinadynamicandunpredictableantigenicenvironment.Annu.Rev.Immunol.17,221–253(1999).CAS  PubMed  GoogleScholar  Zheng,L.,Li,J.&Lenardo,M.Restimulation-inducedcelldeath:newmedicalandresearchperspectives.Immunol.Rev.277,44–60(2017).CAS  PubMed  GoogleScholar  Mueller,S.N.,Gebhardt,T.,Carbone,F.R.&Heath,W.R.MemoryTcellsubsets,migrationpatterns,andtissueresidence.Annu.Rev.Immunol.31,137–161(2013).CAS  PubMed  GoogleScholar  Sade-Feldman,M.etal.DefiningTcellstatesassociatedwithresponsetocheckpointimmunotherapyinmelanoma.Cell175,998–1013.e20(2018).CAS  PubMed  PubMedCentral  GoogleScholar  Azizi,E.etal.Single-cellmapofdiverseimmunephenotypesinthebreasttumormicroenvironment.Cell174,1293–1308.e36(2018).CAS  PubMed  PubMedCentral  GoogleScholar  Pauken,K.E.etal.EpigeneticstabilityofexhaustedTcellslimitsdurabilityofreinvigorationbyPD-1blockade.Science354,1160–1165(2016).CAS  PubMed  PubMedCentral  GoogleScholar  Gide,T.N.etal.Distinctimmunecellpopulationsdefineresponsetoanti-PD-1monotherapyandanti-PD-1/anti-CTLA-4combinedtherapy.CancerCell35,238–255.e6(2019).CAS  PubMed  GoogleScholar  DownloadreferencesAcknowledgementsThisworkwassupportedbytheDivisionofIntramuralResearch,NationalInstituteofAllergyandInfectiousDiseases,NIH.A.D.W.wassupportedbytheEmoryUniversityMD/PhDProgram,NIHMD/PhDPartnershipsProgramandNIHOxford–CambridgeScholarsProgram.J.M.F.wassupportedbythePostdoctoralResearchAssociateTrainingProgramoftheNationalInstituteofGeneralMedicalSciences.TheauthorsthankR.Kissingerforhelpwiththeillustrations.TheythankG.DeLucaforhissupportofA.D.W.asaDPhilco-mentor.TheyalsothankY.Zhangforinvaluableeditorialandscientificfeedback.Lastly,theauthorsacknowledgeandapologizetoallresearchersinthisfieldwhomayhaveauthoredelegantstudiesthatwerenotcitedowingtospacelimitations.AuthorinformationAuthorsandAffiliationsMolecularDevelopmentoftheImmuneSystemSection,LaboratoryofImmuneSystemBiology,NationalInstituteofAllergyandInfectiousDiseases,NationalInstitutesofHealth,Bethesda,MD,USAAlexD.Waldman, JillM.Fritz & MichaelJ.LenardoClinicalGenomicsProgram,DivisionofIntramuralResearch,NationalInstituteofAllergyandInfectiousDiseases,NationalInstitutesofHealth,Bethesda,MD,USAAlexD.Waldman, JillM.Fritz & MichaelJ.LenardoAuthorsAlexD.WaldmanViewauthorpublicationsYoucanalsosearchforthisauthorin PubMed GoogleScholarJillM.FritzViewauthorpublicationsYoucanalsosearchforthisauthorin PubMed GoogleScholarMichaelJ.LenardoViewauthorpublicationsYoucanalsosearchforthisauthorin PubMed GoogleScholarContributionsTheauthorscontributedequallytoallaspectsofthearticle.CorrespondingauthorCorrespondenceto MichaelJ.Lenardo.Ethicsdeclarations Competinginterests Theauthorsdeclarenocompetinginterests. AdditionalinformationPeerreviewinformationNatureReviewsImmunologythanksJ.Oliaroandtheother,anonymous,reviewer(s)fortheircontributiontothepeerreviewofthiswork.Publisher’snoteSpringerNatureremainsneutralwithregardtojurisdictionalclaimsinpublishedmapsandinstitutionalaffiliations.GlossaryNeoantigens Antigensnotexpressedbyself-tissuesundernormalconditionsthatmanifestinthecontextofpathology;incancer,thesecouldbealteredproteins/peptidesencodedbymutatedgenes. Immunecheckpoint Amechanismofimmunecellinhibitionthatrestrainsactivation. Immunoglobulinsuperfamily Agroupofproteinswithgeneticandstructuralsimilaritiestoantibodies. Antigen-presentingcells (APCs).Immunecellsinvolvedintheuptakeandprocessingofantigenstoinitiatecellularimmuneresponses. CTLA4Ig SolublerecombinanthumancytotoxicTlymphocyteantigen4(CTLA4)fusedtotheimmunoglobulinFcdomainthatcompeteswithendogenousCD28foritsligands. Immunologicalsynapse Aninterfacebetweeninteractinglymphocytesandantigen-presentingcellsthatcontrolsantigen-inducedsignalling. Immuneconjugate Abiologicalunitthatcomprisesinteractinglymphocytesandantigen-presentingcells. IL-2 Acytokineessentialforlymphocyteactivation,proliferationandtolerance. Adaptorprotein Anintracytoplasmicproteinthatfacilitatesmolecularinteractionsandsignaltransduction. Antibody-dependentcell-mediatedcytotoxicity Theprocessbywhichantibody-basedopsonizationoftargetcellspromotestheirlysisbyimmunecytotoxiccells. BALB/c Analbinoinbredmousestraincommonlyusedinimmunologyresearch. Non-obesediabetic Aninbredmousestainwithenhancedsusceptibilitytospontaneousdevelopmentoftype1diabetesmellitus. Immunoreceptortyrosine-basedswitchmotif Aconservedaminoacidsequence(TxYxx(V/I))involvedinbothactivationandinhibitionofdownstreamsignallingdependingonthecelltypeandbiologicalcontext. Immunoreceptortyrosine-basedinhibitorymotif Aconservedaminoacidsequence(S/I/V/LxYxxI/V/L)involvedintherecruitmentofinhibitoryphosphatasestodampendownstreamsignalling. Tcellexhaustion Theprogressivelossofeffectorfunctionduetochroniclow-affinityantigenstimulation. Abscopalresponses Aphenomenoninwhichthetherapeuticeffectofradiationisextendedbeyondtheboundariesofthetissuethatwastreated Thelper2(TH2)cellskewing BiasingofCD4+Thelpercellstowardsaphenotypeessentialforhumoralimmunity. RightsandpermissionsReprintsandPermissionsAboutthisarticleCitethisarticleWaldman,A.D.,Fritz,J.M.&Lenardo,M.J.Aguidetocancerimmunotherapy:fromTcellbasicsciencetoclinicalpractice. 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