mRNAsarethemoleculartemplatesforthesynthesisofproteins.Ineukaryoticorganisms,theprimarygenetranscripts,pre-mRNAs,aretypicallynotfunctionalforproteinsynthesisuntilinternalsequences(introns)areremovedandtheremainingfragments(exons)aresplicedtogethertogeneratematuremRNAs(Fig.1).Indeed,pre-mRNAsplicingisessentialfortheexpres-sionof>95%ofhumangenes1,2.TheprocesscanalsoberegulatedtogeneratealternativelysplicedmRNAs(Fig.2)thatencodedistinctproteinvariants,whichisamecha-nismoftenusedtomaintaincellularhomeostasisandtoregulatecelldifferentiationanddevelopment1,2.Thesplicingprocessanditsregulationarehighlyrelevantforunderstandingeveryhallmarkofcancer(Fig.2,SupplementaryTable1),tothepointthatsplic-ingalterationsconstituteanothercancerhallmark3–8.Forexample,analysesof>8,000tumoursacross32can-certypesrevealedthousandsofsplicingvariantsnotpresentinnon-malignanttissues,whicharelikelytogeneratecancer-specificmarkersandneoantigens9,10thatcouldpotentiallybeusedasmRNAvaccines11.Asanotherexample,thegenerationofsplicingvar-iantsisfrequentlyresponsiblefortheacquisitionofresistancetoandrogenreceptor-targetedtherapiesinprostatecancerandforresistancetovemurafenibinmelanoma12–14.Inaddition,resultsindicatethatcancercellsimposespecialdemandsonthesplicingmachin-erysuchthattheybecomeparticularlyvulnerabletosplicingperturbations,afeaturethatisbeginningtobeexploitedpharmacologically15–18.InthisReview,weoutlineindetailthesplicingprocessanditsalterationsincancerbeforehighlightingopportunitiesforthedevelopmentofinnovativetherapeuticapproachesinclinicaloncology.ThesplicingmachineryandcancerTheremovalofintronsinvolvesachemicalmechanismbywhichspecificphosphodiesterbondsinthepolynu-cleotidechainsofRNAareexcised,andnewonesareformed.Thisprocessoccursintwoconsecutivestepsandinvolvestheformationofanunusual2′–5′phos-phodiesterbondbetweenthe5′nucleotideoftheintronandakeyinternaladenosineresidue(thebranchsite)located15–30nucleotidesupstreamofthe3′endoftheintron(Fig.1).Thischemicalmechanismisidentical...
