Download Background

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