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Sanaktekin, Ida_Senior Thesis 2026

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Modeling

Senior Thesis | 2026

PredictingCAR-TCellTherapyResponseinMultipleMyeloma ThroughSingle-CellAIModeling

IdaSanaktekin

ThesisAdvisor:Mr.Seth

Introduction

Multiplemyeloma(MM)isthesecondmostcommonbloodcancer inhumansandoccursinthebonemarrow,specificallyinplasma cells.Normally,plasmacellsdevelopfromBcellsandproduce diverseantibodiestosupportimmunedefenseagainstpathogens. InMM,amutatedplasmacellmultipliesintoalargeclonethat producesonlyonetypeofantibody,knownasmonoclonalprotein (M-protein),whichdoesn’thaveausefulimmunefunction.Asthe cancerprogresses,therisinglevelsofMproteinbeginto accumulateinthetissue,thickentheblood,andcontributedirectly toorgandamage.1

MMisthemalignantendofabiologicalspectrumthat beginswithmonoclonalgammopathyofundeterminedsignificance (MGUS)andprogressesthroughsmolderingmultiplemyeloma (SMM)beforesymptomaticMM.Intheseearlierstages,abnormal plasmacellsthatproduceM-proteinarealreadypresentinthebone marrow,buttheyhaven’tyetacquiredallthegeneticfeatures necessarytocausetissuedamage.Overtime,theseplasmacells mayaccumulateadditionalmutationsandexpandmore aggressively. Whiletheexactcauseofthediseasehasnotbeen identified,riskfactorsincludegenderandage.MMisprevalentin peopleover65,mostofwhicharemen. 2,3

Thebonemarrowmicroenvironmentplaysacrucialrolein thedevelopmentandprogressionofMM.Withinthisniche, stromalcells,connectivetissuecellsthatprovidestructural support,releasegrowthfactorssuchasIL-6thatpromotethe survival,migration,andproliferationofmyelomacells.Adhesion moleculesalsoacceleratediseaseprogressionbyanchoring myelomacellsinplaceandfuelingtheirgrowth.3 Moreover, myelomacellshavedevelopedvariousstrategiestoevadeimmune response.First,theydownregulatetumorantigensthattheimmune cellsrecognizeandtargetforremoval.Second,thegrowthfactors thatmyelomacellssecretedrivetheexpansionandactivationof regulatoryTandBcells,whosejobitistodirectlysuppress

immunemechanismsthatwouldotherwiseeliminatemalignant plasmacells.Thesedynamiccellularinteractionscontributetoa notableheterogeneityobservedamongMMpatients,meaningthat diseasecanvarywidelyfromoneindividualtoanotherintermsof cellularcomposition,diseaseprogression,andtreatment response.4,5

Anoveltherapythathaslatelyshownpromisingeffectsin cancertreatmentischimericantigenreceptorT(CAR-T)cell therapy,whichinvolvesgeneticallymodifyingthepatient’sownT cellsinalabtoproducesyntheticreceptorscalledchimericantigen receptorsthatcanrecognizespecificantigensonthesurfaceof cancercells.Onceexpandedandinfusedbackintothepatient,the engineeredTcellscanselectivelyidentifyandkillthetargettumor antigens. 6 Thistreatmentapproachappearsmosteffectivefor bloodcancerslikeMM,becauseTcellscirculateinthebloodjust likethecancercellsdo.Thisphysicalaccessibilitymeansthat CAR-Tcellscanencounterandtargetcancercellswithoutneeding topenetratedensetissuesorcrossphysicalbarriers.7 Although CAR-Tcelltherapypromisesmoretargetedandindividualized cancertreatment,itsefficacyremainslimitedbyitssevere immune-relatedsideeffectsandthevariabilityseeninpatients’ treatmentresponse.WhileCAR-Tcellsdon’texpandandpersistin somepatients,robustproliferationoccursinothers.Thepredictive indicatorsandmechanismsassociatedwithsuccessfulproliferation arestillpoorlyunderstood,whichhighlightstheneedfora techniquethatcanidentifybiomarkersthatdistinguishpotential respondersfromnon-responders. 6

Inthisstudy,weintegratedpubliclyavailablesingle-cell RNA-seqdatasetsspanningMGUS,SMM,andMMwiththegoal ofbuildinganAImodelthatcancharacterizecellular heterogeneityacrossdiseasestages,distinguishhealthycellsfrom unhealthycells,andpredictpatientresponsetoCAR-Tcell therapy.

Single-CellRNASequencing

RNAsequencingisamolecularbiologytechniqueusedto determinewhichRNAmoleculesarepresentinacellandinwhat quantities.Itallowsresearcherstoidentifywhichgenesareturned on,compareexpressionlevelsacrossconditions,andtrackhow geneexpressionchangesovertimeorinresponsetodisease.Over thepastdecade,thistechniquehasprovedtobeapowerfultoolin cancerresearchforuncoveringgeneexpressionpatternsthatdrive tumordevelopmentandprogression. 8

TraditionalRNAsequencing,knownasbulksequencing, measuresgeneexpressionbyanalyzingRNApooledfrommillions ofcellswithinatissuesample.Whilethisapproachisusefulfor identifyingbroadtrends,itgeneratesanaverageexpressionprofile thatoverlooksthesubstantialheterogeneitythatexistsamong individualcellsincomplextissuessuchastumors. 8,9 Singlecell RNAsequencing(scRNA-seq),whichhasgainedpopularityinthe pastfewyears,overcomesthelimitationofbulksequencingby measuringgeneexpressionatthelevelofindividualcells.By isolatingandsequencingRNAfromthousandsofindividualcells simultaneously,scRNAmakesitpossibletodistinguishdistinct celltypesandstatespresentinasample.Thishigh-resolutionview alsoallowsresearcherstodetectraresubpopulationsthatplaya criticalroleindiseaseprogressionandthatwouldotherwisebe obscuredbybulksequencing.

Figure 1. Experimentalstepsofsingle-cellRNAsequencing10

scRNA-seqdataaretypicallygeneratedexperimentallyin molecularbiologylabs.ThestepsareshowninFigure1.First,a bonemarrowsampleiscollectedfromadonorandenzymatically brokendownintoindividualcells.Theresultingcellsuspensionis thenloadedintoamicrofluidicdevicecalled10xGenomics Chromium,whichcaptureseachcellinatinyoildropletalong withabarcodedbead.Wheneachcelllyses,itsmessengerRNA (mRNA)bindstothebarcodedbeads.Theuniquebarcodeensures thateverymRNAmoleculecanlaterbetracedbacktoitsoriginal cell.ThecapturedRNAisthenreverse-transcribedtocDNA, amplified,sequenced,andcomputationallyprocessedtoquantify geneexpressionforeverycell.Thefinaloutputisagene expressionmatrixinwhicheachcolumncorrespondstoagene, eachrowcorrespondstoanindividualcell,andeachvalue representstheabundanceofagivengeneinagivencell.

Sincetheinventionofsingle-cellRNAsequencing,vast collectionsofsingle-celldatahavebecomeavailableacross tissues,conditions,anddiseasescontexts.Manyrecentscientific studiessoughttointegratethesesingle-celldatasetstoaddress complexbiologicalquestions;however,thetechnicaland biologicalheterogeneityarisingfromdifferencesinsample collectionmethods,sequencingplatforms,andlibrarypreparation protocols,whichareprocessesusedtoconvertRNAintobarcoded, sequencing-readyDNAfragments,posedasignificantchallengeto effectivedataintegration.Thislimitationincreasedtheneedfor unifiedmodelscapableofintegratingdiversesingle-celldatasets. 11

Meanwhile,computermodelscalledtransformer architectureshadrevolutionizedlanguageprocessingbycapturing intricaterelationshipsindata.Thesearchitecturespavedtheway forthedevelopmentoffoundationmodels,whicharelarge-scale andself-supervisedAImodelstrainedonvastdatasetsthatcanbe adaptedtovariousdownstreamtasks.Inspiredbythisadvancement inlanguageprocessing,researchersleveragedthesame transformer-basedarchitecturetocreatesingle-cellfoundation modelsthatcanbetrainedondiversedatasetsandanalyze underlyingpatternsinbiologicaldata.

Single-cellGenerativePre-trainedtransformer(scGPT)isa transformer-basedfoundationdesignedspecificallyforsingle-cell biology.Insteadofwords,scGPTtakesgenesasitsbasicunits,and insteadofsentences,itworkswithindividualcells.Theinputto scGPTconsistsofthreemaincomponents:genetokens,expression values,andconditiontokens.Genetokensfunctionasunique identifiersforeachgene,allowingthemodeltorecognizeand learnrelationshipsbetweenspecificgenesacrossmanycells. Expressionvaluesindicatehowstronglyageneisexpressedwithin agivencell.Conditiontokensprovideadditionalcontextaboutthe cell,suchasdiseasestage,treatmentstatus,ordatasetoforigin.

Thisstructureenablesthemodeltocomparecellswhileaccounting forbiologicalcontext.Eachcellinitiallyhasexpressionvaluesfor thousandsofgenes,whicharehigh-dimensionalanddifficultto comparedirectlyacrosscellsanddatasets.ScGPTtransformsthis high-dimensionalinformationintoafixed-lengthvector,also calledanembedding,thatcapturesthekeypatternsingene expressionwhilediscardingredundantinformation. 12,13

Thecoremechanismoftransformermodelsis self-attention,whichenablesthemodeltoconsiderallelementsof theinputatthesametimeandlearnhowtheyrelatetooneanother. Inlanguagemodels,thislearningisachievedthroughaspecial kindofself-attentioncalledcausalmaskedattention,wherethe modeltriestopredictthenextwordsolelybasedonthe informationfrompreviouswords.AlthoughscGPTandGPT languagemodelssharethesamearchitecture,they’reinherently differentduetothenon-sequentialnatureofbiologicaldata.Unlike wordsinasentence,theorderofgenesisinterchangeable,and thereisnospecific‘nextgene’topredict.Thiscoredifference makesithardtoapplythesamemaskedlearningformulationused inGPTmodelstoscGPT.Insteadofenforcingwordorder,scGPT usesmaskedself-attentiontohidetheexpressionvaluesofcertain genesandchallengeitselftopredictthemissingvaluesbasedon theremainingones.Itexamineswhatgenestendtoturnon togetherandworktowardthesamegoal,orwhatgeneshave opposingeffects.Byrepeatingthistaskacrossmillionsofcells,it ultimatelylearnsthefundamentaltranscriptionalpatternsthat defineacell’sstateandfunction. 12

Methods

ComputationalAnalysis

Inthisstudy,scRNA-seqdatawerenotdirectlygenerated inthelabbutratherobtainedthroughthedatabaseGene ExpressionOmnibus(GEO),specificallythedatasetsGSE163278,

GSE161195,GSE120221,GSE124310,GSE156728, phs002476.v1.p1,GSE106218,GSE124310,GSE271107,and thosestoredinhumanatlas.Weusedsinglecelldatafrompatients acrossdifferentstagesofMMandhealthydonors.Thecollected dataunderwentpre-processinginScanpy,apythontoolkit specificallydesignedforanalyzingsingle-celldata.

Thefirststepwasqualitycontrol(QC),whichinvolved filteringoutcellsthatweredamagedorcapturedlittletonoRNA duringtissueprocessing.KeyQCmetrics,includingthenumberof detectedgenes,totalRNAcounts,andmitochondrialgene expressionpercell,werevisualizedusingviolinplotstoassess dataqualityandidentifyfilteringthresholds.13 Cellswithhigh mitochondrialcounts,whichisindicativeofcellularstressorcell death,andcellswithlowtotalRNAcountswereexcludedfrom downstreamanalysis.Additionally,genesexpressedinveryfew cellswerealsoremovedtoreducethecomputationalload.Figure2 showsviolinplotsusedforoneofthedatasets.Eachdotonthe plotsrepresentsacell.Althoughmostcellsshowedlow mitochondriaexpression,asubsetdisplayedelevatedvalues consistentwithstressedorlowqualitycellsandweretherefore removedduringQC.

Figure2.Violinplotsvisualizingthenumberofdetectedgenes,totalRNA counts,andmitochondrialgeneexpressionpercell,respectively.

Thenextstepwasnormalizationandscaling.Thequantity ofmRNAcapturedfromeachcellmayvaryduetobiological differencesortechnicalfactorsintroducedduringcellisolationand sequencing.Thesetechnicaldifferencescreatebiasesinthedata:a cellwithmoretotalcountswillappeartoexpresseverygeneata higherlevel,evenifthatisnotactuallythecase.Normalization addressesthisproblembyrescalinggeneexpressionvaluesineach cellaccordingtohowmuchtotalmRNAwascaptured.Inother words,itmakesgeneexpressionvaluescomparableacross differentcells.14,15 Figure3illustratestheeffectofnormalization. Intherightpanel,genesdisplayabroadrangeofvariabilitythat increaseswithmeanexpression.Ontheotherhand,intheleft panel,normalizationremovesthisexpression-dependent relationship,causingmostgenestoclusteraroundtheexpected baseline,whichis0(thisnumbermightvarydependingonthe dataset),whilehighlightingasubsetofgenes(representedwith blackdots)withunusuallyhighcell-to-cellvariability.Thisallows highlyvariablegenestobeaccuratelyidentifiedandselectedfor downstreamanalysis,whichisacrucialcomponentofthe computationalworkflow,sincehighlyvariablegenesaretheones thatdistinguishcellsfromoneanothermosteffectively.

Figure3.Scatterplotsshowingmeanexpressionofgenesversusdispersion beforeandafternormalization.

Normalizationwasfollowedbydimensionalityreduction. Eachcellcanhaveexpressionlevelsforthousandsofgenes,which createsahigh-dimensionaldatasetthatisveryhardtovisualize, cluster,andinterpret.Dimensionalityreductioncompressesthe informationintoasmallernumberofdimensionsthatstillcapture themajorsourcesofvariationacrosscells,whichmakesthe subsequentstepsmucheasierandmoreeffective.14 Principal componentanalysis(PCA)wasusedastheprimarydimensionality reductionmethod,whichtransformedtheoriginalgeneexpression matrixintoanewsetofvariablescalledprincipalcomponents, eachofwhichrepresentsadistinctdirectionofvariationinthe data.Todecidehowmanydimensionstokeepfordownstream analysis,PCAvarianceratiowasexamined,whichindicatesthe fractionoftotalvarianceexplainedbyeachprincipalcomponent (PC).AsshowninFigure4,thefirstfewPCscapturethemajor sourcesofvariationinthedataset.AsadditionalPCsareincluded, eachsuccessivecomponentexplainsasmalleramountofvariance, whichisreflectedinthegradualflatteningofthecurve.Basedon thevarianceprofile,acutoffwasselectedatthepointwherethe varianceratiobegantoleveloff,andonlythePCsprecedingthis cutoffwereretainedfordownstreamanalysis.

Figure4.Varianceexplainedbyprincipalcomponentsrankedindecreasing order

Asthequality-controlstep,cellswerevisualizedinscatter plotsusingthefirsttwoprincipalcomponents,PC1andPC2, whichrepresentthedirectionswherecellsdifferthemostoverall. ToconfirmtheaccuracyofPCAandassesswhetherthe differencescapturedbyPC1andPC2reflectedrealbiologyrather thanrandomvariation,cellswerecoloredbytheexpressionofa knownmarkergene,suchasNO2CL,asshowninFigure5.Ifcells withhighexpressionofagivenmarkeroccupiedaspecificregion ofthePCAplotinsteadofbeingrandomlyscattered,thisindicated thatthevariationcapturedbyPCAcorrespondedtorealbiological differencesbetweencells.

Figure5 Scatterplotofcellsprojectedontothefirsttwoprincipalcomponents (PC1andPC2),coloredbyNOC2Lexpression.

AsseeninFigure5,eachcellwasrepresentedasapointin alower-dimensionspaceafterPCA.AK-nearestneighbors(KNN) algorithmwasthenappliedtocalculatethedistancebetweena givencellandallothercellsinthisPC-reducedspaceandidentify, foreachcell,kclosestcellsasitsneighbors.Repeatingthisprocess foreverycellgeneratedacell-cellgraph,whereeachcellwas connectedtoitsneighborsbasedongeneexpressionprofile.This graphprovidedafoundationforapplyingtheLeidenalgorithm, whichpartitionedcellsintoclusters.Leidenwasrunatmultiple

differentresolutions(resolution=0.4,0.6,and1.4)toidentifythe bestscaleforclustering.UniformManifoldApproximationand Projection(UMAP)plots,showninFigure6,werethenusedto generatetwo-dimensionalvisualmapsofdistinctclusters.Each clusterwasrepresentedwithadifferentcolor.WhileUMAP visualizationmadeiteasiertoobservepatternswithinthedataand seehowclusterswerearrangedrelativetooneanother,itdidnot informabouttheclusters’biologicalidentity.

Figure6.UMAPvisualizationofsinglecellscoloredbyLeidenclustering.

Todeterminewhateachclusterrepresentedbiologically, cellannotationwasnecessary.Thisprocessinvolvedidentifying markergenesthatweremuchmorehighlyexpressedinonecluster thaninothers.Toidentifythesegenes,weconducteddifferential expressionanalysis,specificallytheWilcoxonrank-sumtest,in whichcellswithinagivenclusterwerestatisticallycomparedtoall remainingcellsinthedataset.Figure6illustratesdifferential expressionanalysisforaclusterinoneofthedatasets.Eachgene wasassignedascore,whichisastatisticalmeasureofhow stronglythatgenedistinguishesoneclusterfromtherest.Genes withthehighestscoreswereconsideredthemostinformative markers.Tovalidatetheaccuracyofmarkergenesidentifiedby Wilcoxonrank-sumtest,resultswerecomparedwiththose

obtainedusingat-test,andoverlapbetweenthetwomethodswas assessedusingavenndiagram.

Figure7 DifferentiallyexpressedmarkergenesforLeidencluster0identified byone-versus-restcomparison

Heatmapswerethengeneratedtovisualizetheexpression patternsoftopmarkergenesidentifiedbyWilcoxonrank-sumtest. Intheheatmaps,suchastheoneillustratedinFigure7,rows correspondedtodifferentclustersobtainedusingLeiden,whereas columnscorrespondedtomarkergenesrankedbytheirdifferential expressionscores.Thecolorintensityreflectedrelativeexpression levels,whichallowedclearvisualizationofgenesthatwerehighly expressedinspecificclustersandlowinothers.Thetopmarker geneswerematchedtowell-knownmarkersfrompublished studies,databasesorreferenceatlases.Basedonthiscomparison,a biologicalidentitywasassignedtoeachcluster,enablingusto interpretthecellularcompositionofthebonemarrow microenvironmentindifferentpatients.

Figure8.Heatmapshowingcluster-specificmarkergeneexpressionacross Leiden-definedcellpopulations

TrainingscGPT

FollowingstandardscRNA-seqpreprocessingandanalysis, curatedgeneexpressionmatriceswereusedasinputforscGPT modeltraining.Themodelwastrainedintwostages:pre-training andfine-tuning.Duringpre-training,scRNA-seqdatafromall sampleswereusedwithoutcelltype,diseasestate,ortreatment responselabels,enablingthemodeltolearngeneralgene expressionstructureandcell-staterepresentationsina self-supervisedmannerthroughmaskedgenemodelingand self-attentionmechanisms.

Theprojectiscurrentlyatthebeginningofthefine-tuning process,wherethepre-trainedmodelwillbeadaptedtospecific downstreamtasksusingadditionalcontextualinformation, includingcell-typeannotations,diseasestagelabels,and treatment-relatedmetadata.ForCAR-Tcellresponseprediction, allsinglecellsfromeachpatientwillbetreatedcollectivelyasa set.Withinthemodel,thesecellswillbecombinedusingan attention-basedpoolingmechanismthatlearnstoassigndifferent weightstodifferentcellsbasedontheirrelevancetotreatment outcome.Cellswhosetranscriptionalprofilesareconsistently associatedwithresponseorresistancewillreceiveahigher attentionweight,whilethosethatcontributeminimallywillreceive alowerscore.Thisweightedaggregationwillproduceasingle patient-levelembeddingwhichwillthenbepassedtoaprediction

layerinsidethemodel.Thislayerisasimplesupervisedclassifier thatwillbetrainedusingknownclinicaloutcomes.During training,themodelwillrepeatedlycompareitspredictedresponse withthetrueresponselabel(responderornon-responder)and adjustitsinternalparameterstoreducepredictionerror.Overtime, theclassifierwilllearnhowspecificpatternsinthepatient-level representationcorrespondtosuccessfulorunsuccessfulCAR-T treatment.

Whenappliedtoanewpatient,thesamestepswillbe followed:thepatient’ssingle-celldatafrombonemarrowwillbe aggregatedintopatient-levelrepresentationusingattention weights,andthenfedintothepredictionlayer.Theoutputofthis layerwillbearesponsescore,typicallyinterpretedasthe probabilityofCAR-Tcelltherapyresponse.Athresholdonthis probabilitywillthenbedeterminedtoclassifywhichpatientsfall intotheresponderornon-respondercategory.

Results

Figure9.UMAPvisualizationoftheintegrateddatasets,coloredbydataset source

Weintegrated14publiclyavailabledatasetsspanning normalbonemarrow(NBM),MGUS,SMM,andMM.After qualitycontrolandfiltering,2,616,376cellswereretainedfor downstreamanalysis,1.56%beingMGUS,1.57%beingSMM,

59%beingMM,38%beingNBM.Wecollectedimmune-celldata frompatientsacrossawideagerange,withameanageof44.94 years( 6.32).UMAPvisualizationoftheintegrateddataset± coloredbydatasetsourceshowedextensivemixingofcellsfrom differentstudies,withnodatasetforminganisolatedcluster.This overlapindicatessuccessfulintegration.TheUMAPvisualization infigure9wascoloredbydiseasestage.Normalbonemarrow cellswerewidelydistributedacrosstheembedding.Asdisease progressedfromMGUStosymptomaticMM,theredclusters localizedincertainregionsoftheUMAP,formingdenserareas, buttheystilloverlappedsignificantlywithearlierstages.This findingalignswiththebiologicalunderstandingthatthemalignant transformationinMMisgradual.

Figure10.UMAPvisualizationoftheintegrateddatasets,coloredbydisease stage

Figure11representsthe UMAPembeddinggeneratedafter thefinaldifferentialexpressionanalysisofallscRNA-seqdatasets includedinthisstudy.Thevisualizationrevealsdistinctclusters correspondingtomultiplebonemarrowpopulations,including malignantplasmacellsaswellasdiverseimmunecelltypessuch asTcells,Bcells,NKcells,andmyeloidpopulation.Withinthe

lymphocytepopulations,bothnaiveandmemoryTandBcells wereidentifiable,whichshowsthatthedatasetcapturesfunctional immunestatesinadditiontocellidentity.Thisdiversityis particularlyimportantforpredictingCAR-Tcelltherapyresponse, becauseCAR-Tcelltherapyworksbygivingpatientsliving immunecellsthatmustmultiplyandremainactiveinthebodyto keepthecancerundercontrol,sotreatmentsuccessdependsnot onlyonthecanceritself,butalsoonhowhealthyandsupportive thepatient’simmunesystemis.Thepresenceofdifferentimmune cellstateslikenaiveandmemorylymphocytesthereforesuggests thatthedatasetcontainsbiologicallyrelevantinformationthatcan helpexplainwhysomepatientsrespondtoCAR-Ttherapywhile othersrelapse.

Figure11.UMAPvisualizationofdifferentcelltypesandimmunestatesthat existinallofthedatasetscollected

Discussion

Acentralobjectiveofthestudyistocreateacomputational frameworkcapableofcapturingcellularheterogeneityrelevantto therapeuticresponse,particularlyinthecontextofCAR-Tcell therapy.Althoughpredictiveperformancehasnotyetbeentested inthefine-tuningstage,theoverlappingtranscriptionalstatesin UMAPSacrossdiseasestagesunderscoretheneedformodelsthat canmovebeyondsimpleclusteringandanalyzeunderlying gene-geneinteractionsandcellularfeaturesthatcharacterizethe bonemarrow.Afterbothpretrainingandfinetuningarecompleted, thescGPTmodelisexpectedtoserveasaclinicallyimportanttool

foranalyzinganewpatient’sbonemarrowprofileinrelationto previouslyanalyzeddataforbothCAR-Tcelltherapyresponders andnon-responders,supportingmoreinformedandindividualized treatmentdecisions.

Limitations

Thisstudyhasseverallimitationsthatshouldbetakeninto account.First,theanalysisreliesonsingle-cellRNA-seqdata derivedfrombonemarrowsampleswhichareobtainedfroma painfulprocesscalledbonemarrowaspiratebiopsythatalotof peopleareunwillingtoundergo.Asaresult,thecurrentlyavailable datasetsarelimitedinsizeandmaynotfullyrepresentthe diversityofthepatientpopulations.Second,althoughmultiple diseasestageswereincluded,clinicalmetadatawereunevenly distributed,meaningthatanunequalnumberofpatientsineach diseasestagewereevaluatedforthestudy.MoreMGUSandSMM dataneedtobecollectedinordertoobtainamoreaccurate representationoftranscriptionalandcellularstatesthatdefineeach diseasestageortherapeuticresponse.Thegoalistotrainthe scGPTmodelonatleast10millioncells.

FutureDirections

FutureworkwillfocusonexpandingthescGPTtrainingto includedatafrompatientsdiagnosedwithothertypesofblood cancerssuchasleukemia,wheresimilarchallengespertainingto cellularheterogeneityandtreatmentresponseremain.Moreover, thecomputationalframeworkoffersanopportunitytoaddress unresolvedbiologicalquestionsinMM,suchastheheterogeneity seeninSMMpatients.Asmentionedintheintroduction,SMMis theintermediatestageonthediseasespectrum.SomeSMM patientscloselyresemblethosewithMGUSandexhibitveryslow diseaseprogression,oftennotrequiringimmediatemedical intervention.Ontheotherhand,someSMMpatientsclosely resembleMMandprogressrapidly,whichindicatesaneedfor

earlymedicalintervention.BecausethescGPTmodelcan differentiatethebonemarrownicheacrossdiseasestages,itcan distinguishMGUS-likefromMM-likeSMMpatients. Thisclassificationhasthepotentialtoprovideinsightinto progressionriskandallowclinicianstomakemoreinformed decisionsastowhetherandwhenatreatmentshouldbeinitiated.

AdditionalImplicationsforTherapeuticResponse

Inadditiontodiseasestageandcell-composition,immune aging,definedastheageofone’simmunesystem,maybea potentialcontributortovariabilityinCAR-Tcelltherapyresponse. CAR-Tcellsdependonthefunctionalcapacityofapatient’s immunesystemforsuccessfulexpansion,persistence,andtumor killingactivityafterinfusion.Astheimmunesystemages,Tcells oftenexhibitreducedproliferativecapacity,increasedimmune exhaustion,andalteredinflammatorysignaling,allofwhichcan compromiseCAR-Tcelltherapy’sperformance.Importantly, althoughchronologicalageinfluencesimmuneage,itisnotthe onlydeterminingfactor.Patientsofsimilaragemaydisplay remarkablydifferentimmunecellstatesduetofactorssuchasprior treatments,diseaseburden,andcumulativeimmunestress.Asa futuredirection,scGPT-derivedembeddingscouldbeusedto quantifyimmuneagewithinmajorimmunecelltypes,and patient-levelmeasurementscouldbeevaluatedatbaselineand earlypost-treatmenttimepoints.Exploringimmuneageatthe singlecelllevelmaythereforerepresentabiologicallyplausible avenueforunderstandingvariabilityintherapeuticresponseand informouranswertothefollowingquestions:WhydoMM patientsatthesamediseasestageshowdifferentresponsesto CAR-Tcelltherapy?Whydopeopleofsimilaragerespond differently?

Conclusion

Acureformultiplemyelomamaystillbeelusive,but advancementsinRNAsequencingtechniquesandAImodelingare pavingthewayforamorecomprehensiveunderstandingofthe diseasepathophysiologyandthebonemarrowniche,whichplaysa particularlycrucialroleinthediseaseprogressionbyallowing complexinteractionsbetweenmalignantplasmacellsandimmune cellpopulations.

ThisstudyintegrateddiversescRNA-seqdatasetsspanning MGUS,SMM,andMM,andanalyzedthemusingPython, performingstepsincludingpreprocessing,normalization, dimensionalityreduction,clustering,andcell-annotation,toretain onlythebiologicallymeaningfulcellularfeatures.This computationalworkflowprovidedafoundationforbuildinga transformer-basedscGPTmodelthatcanunderstandcellular heterogeneityacrossdiseaseprogression.Moreover,themodelis currentlybeingtrainedtogeneratepatient-levelembeddingsfrom thesingle-celldataofCAR-Tcelltherapyrespondersand non-responders,enablingtheexplorationofresponse-associated immunecellstates.Themodelmaythenbeusedasaclinicaltool foranalyzingnewpatients’bonemarrowandpredictinghowlikely theyaretorespondtoCAR-Tcelltherapy.Aslargerdatasets becomeavailable,thismodelcoulddeepenbiologicalinsightsinto mechanismsoftreatmentresistance,andcontributetothe developmentofmorepersonalizedtherapeuticstrategiesforMM.

Inaddition,theinclusionofpatientsacrossawideage rangecouldallowfortheinvestigationofimmuneagingasa potentialcontributortoCAR-Ttherapyefficacy.Futureworkon themodelpromisesevengreaterimpactbyextendingits applicationtootherbloodcancers,includingleukemia,where similarinteractionsbetweenmalignantcellsandtheimmune microenvironmentinfluencediseaseprogressionandtreatment response.

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