The Genetics of Cancer

Examples of tumor suppressor genes include BRCA1, BRCA2, and p53 or TP53. Germline mutations in BRCA1 or BRCA2 genes increase a woman's risk of developing ... SkiptoContent Español Search Menu YouarehereHome>NavigatingCancerCare>CancerBasics>Genetics>TheGeneticsofCancer RequestPermissions TheGeneticsofCancer ApprovedbytheCancer.NetEditorialBoard,03/2018 GenesareintheDNAofeachcellinyourbody.Theycontrolhowthecellfunctions,including: Howquicklyitgrows Howoftenitdivides Howlongitlives Researchersestimatethateachcellcontains30,000differentgenes.Withineachcell,genesarelocatedonchromosomes.   Aboutchromosomes Chromosomesarethethread-likestructuresincellsthatcontaingenes.Thereare46chromosomes,arrangedin2setsof23. Youinheritonesetfromyourmotherandonefromyourfather.Onechromosomeineachsetdetermineswhetheryouarefemaleormale.Theother22chromosomepairsdetermineotherphysicalcharacteristics.Thesechromosomepairsarecalledautosomes. Howgeneswork Genescontrolhowyourcellsworkbymakingproteins.Theproteinshavespecificfunctionsandactasmessengersforthecell. Eachgenemusthavethecorrectinstructionsformakingitsprotein.Thisallowstheproteintoperformthecorrectfunctionforthecell. Allcancersbeginwhenoneormoregenesinacellmutate.Amutationisachange.Itcreatesanabnormalprotein.Oritmaypreventaprotein’sformation. Anabnormalproteinprovidesdifferentinformationthananormalprotein.Thiscancausecellstomultiplyuncontrollablyandbecomecancerous. Aboutgeneticmutations Thereare2basictypesofgeneticmutations: Acquiredmutations.Thesearethemostcommoncauseofcancer.Theyoccurfromdamagetogenesinaparticularcellduringaperson’slife.Forexample,thiscouldbeabreastcelloracoloncell,whichthengoesontodividemanytimesandformatumor.Atumorisanabnormalmass.Cancerthatoccursbecauseofacquiredmutationsiscalledsporadiccancer.Acquiredmutationsarenotfoundineverycellinthebodyandtheyarenotpassedfromparenttochild. Factorsthatcausethesemutationsinclude: Tobacco Ultraviolet(UV)radiation Viruses Age Germlinemutations.Thesearelesscommon.Agermlinemutationoccursinaspermcelloreggcell.Itpassesdirectlyfromaparenttoachildatthetimeofconception.Astheembryogrowsintoababy,themutationfromtheinitialspermoreggcelliscopiedintoeverycellwithinthebody.Becausethemutationaffectsreproductivecells,itcanpassfromgenerationtogeneration. Cancercausedbygermlinemutationsiscalledinheritedcancer.Itaccountsforabout5%to20%ofallcancers. Mutationsandcancer Mutationshappenoften.Amutationmaybebeneficial,harmful,orneutral.Thisdependswhereinthegenethechangeoccurs.Typically,thebodycorrectsmostmutations.   Asinglemutationwilllikelynotcausecancer.Usually,canceroccursfrommultiplemutationsoveralifetime.Thatiswhycanceroccursmoreofteninolderpeople.Theyhavehadmoreopportunitiesformutationstobuildup. Typesofgeneslinkedtocancer Manyofthegenesthatcontributetocancerdevelopmentfallintobroadcategories: Tumorsuppressorgenes.Theseareprotectivegenes.Normally,theylimitcellgrowthby: Monitoringhowquicklycellsdivideintonewcells RepairingmismatchedDNA Controllingwhenacelldies Whenatumorsuppressorgenemutates,cellsgrowuncontrollably.Andtheymayeventuallyformatumor. ExamplesoftumorsuppressorgenesincludeBRCA1,BRCA2,andp53orTP53. GermlinemutationsinBRCA1orBRCA2genesincreaseawoman’sriskofdevelopinghereditarybreastorovariancancersandaman’sriskofdevelopinghereditaryprostateorbreastcancers.Theyalsoincreasetheriskofpancreaticcancerandmelanomainwomenandmen. Themostcommonlymutatedgeneinpeoplewithcancerisp53orTP53.Morethan50%ofcancersinvolveamissingordamagedp53gene.Mostp53genemutationsareacquired.Germlinep53mutationsarerare,butpatientswhocarrythemareatahigherriskofdevelopingmanydifferenttypesofcancer. Oncogenes.Theseturnahealthycellintoacancerouscell.Mutationsinthesegenesarenotknowntobeinherited. Twocommononcogenesare: HER2,aspecializedproteinthatcontrolscancergrowthandspread.Itisfoundinsomecancercells.Forexample,breastandovariancancercells. TheRASfamilyofgenes,whichmakesproteinsinvolvedincellcommunicationpathways,cellgrowth,andcelldeath. DNArepairgenes.ThesefixmistakesmadewhenDNAiscopied.Manyofthemfunctionastumorsuppressorgenes.BRCA1,BRCA2,andp53areallDNArepairgenes. IfapersonhasanerrorinaDNArepairgene,mistakesremainuncorrected.Then,themistakesbecomemutations.Thesemutationsmayeventuallyleadtocancer,particularlymutationsintumorsuppressorgenesoroncogenes. MutationsinDNArepairgenesmaybeinheritedoracquired.Lynchsyndromeisanexampleoftheinheritedkind.BRCA1,BRCA2,andp53mutationsandtheirassociatedsyndromesarealsoinherited. Challengesinunderstandingcancergenetics Researchershavelearnedalotabouthowcancergeneswork.Butmanycancersarenotlinkedwithaspecificgene.Cancerlikelyinvolvesmultiplegenemutations.Moreover,someevidencesuggeststhatgenesinteractwiththeirenvironment.Thisfurthercomplicatesourunderstandingoftherolegenesplayincancer. Researcherscontinuetostudyhowgeneticchangesaffectcancerdevelopment.Thisknowledgehasledtoimprovementsincancercare,includingearlydetection,riskreduction,theuseoftargetedtherapy,andsurvival. Furtherstudyingcancergeneticsmayhelpdoctorsfindbetterwaysto: Predictaperson’sriskofcancer Diagnosecancer Treatcancer RelatedResources GeneticTestingforCancerRisk UnderstandingCancerRisk HereditaryCancer-RelatedSyndromes WhatIsPersonalizedCancerMedicine? HowGenomicTestingBroughtMeaSenseofControlDuringMetastaticBreastCancer MoreInformation NationalCancerInstitute(NCI):TheGeneticsofCancer NCI:HowGeneticChangesLeadtoCancer(infographic) Español f t k e P Moreinthissection Timely.Trusted.Compassionate. Comprehensiveinformationforpeoplewithcancer,families,andcaregivers,fromtheAmericanSocietyofClinicalOncology(ASCO),thevoiceoftheworld'soncologyprofessionals. FindaCancerDoctor