Single-CellTranscriptomicAnalysisofTumorHeterogeneityHannaMendesLevitin1,JinzhouYuan1,andPeterA.Sims1,2,31DepartmentofSystemsBiology,ColumbiaUniversityMedicalCenter,NewYork,NY10032USA2DepartmentofBiochemistry&MolecularBiophysics,ColumbiaUniversityMedicalCenter,NewYork,NY10032USA3SulzbergerColumbiaGenomeCenter,ColumbiaUniversityMedicalCenter,NewYork,NY10032USAAbstractIntratumoralheterogeneityisamongthegreatestchallengesinprecisioncancertherapy.However,developmentsinhigh-throughputsingle-cellRNA-sequencingmaynowprovidethestatisticalpowertodissectthediversecellularpopulationsoftumors.Inthefuture,thesetechnologiesmightinformselectionoftargetedcombinationtherapiesandenrollmentcriteriaforclinicaltrials.Precisioncancertherapiesexploitpatient-andtumor-specificmolecularfeaturestoattacktransformedcellsormanipulatethetumormicroenvironment.However,thediversityofmalignantandmicroenvironmentalpopulationswithinasingletumorcancomplicatethisapproach.WhilecollaborativemolecularprofilingeffortslikeTheCancerGenomeAtlasihaveenhancedourunderstandingofintertumoralheterogeneityacrosspatients,effortstodissectintratumoralheterogeneityareatamuchearlierstage.Nonetheless,thisinformationislikelycrucialtotherationalapplicationoftargetedtherapies.Thetargetofagivendrugmayonlybepresentinasubsetofcells,andevenifthetargetiswidelyexpressed,itsroleindrivingamalignantphenotypemaybelimitedtoaspecificsubpopulation.Foragiventumortype,therecouldbenumerouspotentialtherapiesorcombinationswhichcouldtarget,eitherbydesignorthroughaside-effect,boththemalignantcellsandthetumormicroenvironment.Whilethesecomplexitiesarewidelyappreciated,thetoolstoassessthemcomprehensivelyarejustnowbecomingavailable.ThedevelopmentofdeepsequencingledtorapidadvancesingeneexpressionprofilingbyRNAsequencing(RNA-Seq).Initssimplestform,RNA-SeqinvolvesconversionofmRNAintoalibraryofamplifiedcDNAfragments,whicharethensequencedandquantifiedtoobtainanexpressionprofile.SoonaftertheintroductionofRNA-Seq,high-sensitivityprotocolsforprofilingindi...
