Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
What is Cancer? Background Information for Teachers f r o m C a n c e rEd Cancerhasbecomeacommonhouseholdtopicofconversation.Overhalfofallmenandathirdofall womenintheU.S.willdevelopcanceratsomepointintheirlifetime.AccordingtotheAmerican ChildhoodCancerOrganization,approximately15,800childrenbetweentheagesofbirthandnineteen willbediagnosedwithcancereachyearintheU.S.Thosethatdonotdevelopcancerthemselvesare verylikelytoknowsomeonethathasthisillness. Cancerisnotasingledisease,butratherasetofdiseasesthatstemfromuncontrolledcellgrowth. Normalcellsdivideintotwohealthy,equaldaughtercells.Cancercells,ontheotherhand,replicateinto abnormalcellsthatdonotrespondtonormalgrowthregulators.Byadulthood,mostcellsinthebody onlydividetoreplaceworn-outanddyingcellsortorepairinjuries.Cancercellshavenoregulation systemsinplaceandthereforereplicateuncontrollably. Cellsthatbecomecancercellsdosoasaresultofdamagetothecell’sgeneticmaterial,DNA (deoxyribonucleicacid).DamagetotheDNAcanresultinmutationsinthegenome.Amutationcanbe categorizedasaskiporadditionintheDNAsequenceora“misspelled”sectionofgenome,resultingin codingofthewrongproteinorlackofproteinproductionneededforpropercellfunctioning.DNAisthe backbonetoallcellactivityandregulation;withoutit,thecellhasnomaporinstructionstofollow. WhentheDNAinhealthycellsisdamaged,thecelleitherrepairsthedamageordies.Whenacelldies,it iscalledapoptosis.Apoptosisis“programmedcelldeath”wherethecellsrecognizecertainbodysignals (i.e.–genemutations,avirus,andotherinfections),whichtriggerthecelltostopdividinginorderto containthespreadofinfectionordisease.CancercellDNAisnotrepairednordoesthecelldieoff; therefore,thecellcancontinuetodivide,creatingmorecellswithdamagedDNA. MostcancersaretheresultofDNAdamageduetoenvironmentalfactors(i.e.smokingorradiation exposure),butinseveralcases,damagedDNAcanbehereditary,whichmeansthedamagedDNAcan bepassedthroughfamilialgenerations.ExamplesofhereditarygenesincludetheBRCAgenes,whichare foundinbreastcancercases,andTP53,whichoccursinmostbonecancers.Amajorityofcancer susceptibilitygenemutationsdon’tleadtochildhoodcancers,howeverfamilialadenomatous polyposis(FAP)doespresentearlyinlife.Withthisinmind,genetictestingofchildrenisnotcommon, butmaybeusefulinmakingfuturedecisionsasanadult. DamagetoDNAcanaffectothergenescalledoncogenesandtumorsuppressorgenes(i.e.p53),which arethebody’snaturalcheckpointsforhealthycellproduction.Ifoncogenesortumorsuppressorgenes detectanerrorinthegenome,in-cellsignalscaneithermarkthecellforrepairormarkthecellfor destruction(apoptosis).If,forsomereason,damagetoacellduetoexternalorinternalfactors(UV, radiation,chemicals,etc.)causesamutationintheDNA,cellproductionisnolongermonitored correctly.CellscanessentiallyskippastthecheckpointsneededtoensurecorrectDNAreplication, sufficientorganelleduplication,andhealthycellgrowth. Uncontrolledcellsmostoftenformtumors(asinmanycommonformsofthedisease)ortheycan remaininthebloodinaformofcancercalledleukemia.Cancercellsspread(metastasize)throughout thebodywhenpartofcancercellstravelintoaperson’sbloodorlymphaticsystemandcontinue abnormalgrowthinnewhealthytissues.Therearetwotypesoftumors:malignantandbenign.Benign tumorsarethosewhichhaveuncontrolledgrowthofabnormalcells,butarenotabletospreadtoother locationsinthebody.Benigntumorsarealmostalwayscurableandhavealowrateofrecurrence. Malignanttumors,ontheotherhand,havetheabilitytomoveintootherareasofthebody,affecting othertissuesandorgans.Bydefinition,canceronlyappliestomalignanttumors.Invasionofcancercells intohealthytissuescompromisesthetissues’specificfunctionsbyeffectivelystealingnutrientsand space(twokeycomponentsneededforhealthytissuegrowth). What is Cancer? a backgrounder from CancerEd Differentcancersgrowandrespondtotreatmentsatdifferentrates;therefore,treatmentisdependent onthetypeandlocationofthecancer.Nocaseislikeanother,andcanceraffectseachperson differently. Cancershaveanoverarchingnamingsystemdependingonwheretheuncontrolledgrowthbegan.For example,ifthecanceroriginatedinthebone,doctorswouldusetheprefixosteo-,whichisLatinfor “bone”.Cancersarealsonamedbasedonwhattypeofcelltheyaffect.Forexample,carcinomasare cancersthataffectinternalandexternalbodysurfaces(i.e.lung,breast,andcolon).Usingthis information,ifapatienthadcanceroriginatinginthesupportingtissue,bone,thedoctorwould diagnosethispatientwithanosteosarcoma.Seebelowforatableofothercommonnamesandprefixes. TypesofCancer PrefixesthatPointtoLocation • • • • Carcinomas–internalandexternalbody surfaces Sarcomas–supportingtissues(i.e.–bone, cartilage,fat,connectivetissue,and muscle) Lymphomas–immunesystemandlymph nodes Leukemias–bloodandbonemarrow • • • • • • • Osteo–bone Adeno–gland Hepato–liver Lympho–lymphocytes Melano-pigmentcells Myelo–bonemarrow Myo–muscle KeyConcepts: • • • • Cancerouscellgrowthisdifferentfromhealthycellgrowthbecauseofitsuncontrolledspeeds, abnormalcellmorphology(shape),andabilitytomigratetonewpartsofthebody. DNAdamagecanbecausedbyenvironmentalcausessuchasUVradiation,smoking,andother lifestylehabits;however,itcanalsostemfromhereditaryorigins,whichiswhysomefamilies havehigherinstancesofcancer. Metastasisisthescientific/clinicaltermforthemovementofcancerfromapointoforiginto othertissuesinthebody.Thisisnormallyanindicationofanadvancedstageofcancer. Oncogenesandtumorsuppressorgenesarethebody’snaturalcheckpointagainstabnormalor damagedcells.Cancercellslackthesegenes,allowingthemtogrowdespitemutationsand abnormalities. SpecialConsiderations: Manystudentsmaybeconcernedwiththefalsehoodthattheycan“catch”cancerfromfamilymembers orfriendswiththedisease.Thisisnotpossible,andshouldbemadeexplicitlycleartostudentsofall ages. Resources: NOTE:Thissectionlistsresourcesthatprovideadditionalbackgroundinformationforteachersaboutthistopic.Additional resourcesincludinginformationforchildren,classroommaterials,andprojectideascanbefoundintheResourcesfile. • • • • AmericanCancerSocietyhttp://www.cancer.org/cancer/cancerbasics/what-is-cancer NationalCancerInstitutehttp://www.cancer.gov/about-cancer/understanding/what-is-cancer AmericanChildhoodCancerOrganizationhttp://www.acco.org/diagnosis/ MedlinePlushttps://www.nlm.nih.gov/medlineplus/cancer.html