MCB$2410$$Gene,cs$Chapter$23$

Cancer'10/29/14$

Transcrip,onal$network$governing$the$angiogenic$switch$in$human$pancrea,c$cancer$

PNAS$2007$104:$12890H12895.$

Cancer'

A$group$of$disorders$characterized$by:$

cell'prolifera-on.$

•  Cells$do$not$respond$to$normal$controls$of$cell$division.$

•  Cells$divide$rapidly$and$constantly$=$tumor$growth.$

•  Crowds$normal$cells$and$robs$nutrients.$

•  Advanced$tumors$shed$cells$that$travel$to$other$parts$of$

the$body$=$metastasis.$

Cancer'Tumor$forma,on$

•  One$or$more$cell$cycle$signals$disrupted.$

=$abnormally$high$rate$of$prolifera,on$(cell$division).$

•  Gradually$lose$normal$shape$and$form$a$dis,nct$mass$

=$Tumor.$$

Benign'tumor$–$cells$remain$localized.$

'Malignant'tumor$–$cells$invade$other$,ssue.'

Cancer'

•  Occurs$in$many$,ssue$types.$

•  public$health$issue.$

•  A$model$to$study$cell$cycle$

control.$

Cancer'A$gene,c$disease$

Early$observa,ons$that$cancer$was$gene,c:$

1.  Many$mutagens$also$cause$cancer.$

2.  Many$cancers$have$recurring$chromosomal$

abnormali,es.$

3.  Some$specific$$cancers$run$in$families.$

(i.e.$re-noblastoma)$$$

Many$cancers$have$chromosomal$abnormali,es.$

Spectral$Karyotyping$Fluorescence$in"situ$hybridiza,on$(SKY'FISH)$

(normal$human$karyotype)$

Many$cancers$have$chromosomal$abnormali,es.$

Normal$human$

karyotype$

Karyotype$of$HCC38$cells.$

(derived$from$breast$cancer)$

•  Hypertriploid.$

•  37$structural$

abnormali,es$involving$

all$chromosomes$except$

6$and$16.$

•  Etc…$

h\p://www.path.cam.ac.uk/~pawefish/BreastCellLineDescrip,ons/HCC38.html$

Many$cancers$have$recurring$chromosomal$abnormali,es.$

Nature$421,$440H444(23$January$2003)$

BurkiA’s'lymphoma''has$a$recurring$reciprocal"transloca.on"between$the$qHarms$of$

chromosomes$8$&$14.$

(Also$see$figure$23.11)$

Knudson’s'mul-step'model'of'cancer.$(1971)$H$Explains$re,noblastoma$

Cancer'is'mul-step.$If$one$or$more$required$muta,ons$are$

inherited,$less$muta,ons$would$be$required$to$produce$cancer.$

Unilateral$

Sporadic$

Bilateral$

Familial$

Clonal'evolu-on'of$a$tumor.'

Indicates$an$

iden,cal$cell.$1st$muta,on$cell$

predisposed$to$

proliferate$faster.$

2nd$muta,on$causes$

cell$to$divide$rapidly.$

3rd$muta,on$cell$

undergoes$structural$

changes.$

4th$muta,on$causes$

cell$to$divide$

uncontrollably$and$

invade$other$,ssue.$

Most$tumors$arise$from$

soma,c$muta,ons$that$

accumulate$in$a$person’s$

life$span.$

The$rate$of$clonal$evolu,on$depends$on$the$frequency$with$which$new$muta,ons$arise.$

Many$cancers$are$influenced$by$environmental$factors.$$

Hong$Kong$

Salt$Lake$City,$Utah$

Types'of'cancer'causing'genes:'Oncogenes$=$Mutated$dominantHac,ng$s#mulatory$genes$that$cause$cancer.$

(protoGoncogene'=$oncogene$prior$to$muta,on)$$

Types'of'cancer'causing'genes:'

Tumor'suppressor'genes'=$Mutated$recessiveHac,ng$

inhibitory$genes$that$cause$cancer.$

Loss'of'heterozygosity'People$heterozygous$for$a$tumorHsuppressor$gene$are$predisposed$to$cancer.$

Loss'of'heterozygosity'oien$leads$to$cancer$in$a$person$heterozygous$for$a$tumorHsuppressor$gene.$

Cell'Cycle'

Cell'Cycle'

Kinase$–$an$enzyme$that$adds$a$phosphate$to$a$protein$

'CyclinGdependent'kinases$(CDKs)$–$kinases$that$control$key$events$of$the$cell$cycle.$

'•  CDKs'are$func,onal$only$when$associated$with$a$

cyclin$(another$protein).$

•  Each$cyclin$appears$at$specific$points$in$the$cell$cycle.$

•  When$bound$to$a$CDK,$which$cyclin$is$present$will$

determine$which$protein$the$CDKs$phosphorylate.$

The$re-noblastoma'protein'helps$control$the$progression$through$

G1/S'checkpoint.$

RB$binds$E2F$and$keeps$it$inac,ve.$

Increasing$conc.$Of$cyclinGDGCDK'and$cyclinGEGCDK'phophorylate$RB.$

Once$phosphorylated,$RB$is$inac,ve$and$releases$E2F.$

E2F$binds$DNA$and$s,mulates$

transcrip,on$of$DNA'replica-on'genes.$

(RB$=$tumor$suppressor)$

Cell$cycle$progression$is$also$regulated$by$

external'factors.$•  Hormones$and$growth$factors$are$unable$to$pass$through$the$cell$

membrane.$

•  Typically$bind$to$cell$surface$receptors$that$transmit$the$message$

into$the$cell.$

='Signal'transduc-on'pathway.'

Example:$Ras'signal'transduc-on'pathway'

•  Inac-ve'Ras$binds$guanosine$diphosphate$(GDP).$

•  Ac-ve'Ras$binds$guanosine$triphosphate$(GTP).'

Example:$Ras'signal'transduc-on'pathway.'

Binding$of$growth$factor$

causes$conforma,on$change$

and$phosphoryla,on.$

Adaptor$molecules$bind$to$

receptor$and$link$to$Ras.$

Ras$binds$GTP$and$is$

ac,vated.$

Example:$Ras'signal'transduc-on'pathway.'

Ac,vated$Ras$ac,vates$Raf.$

Ac,vated$Raf$ac,vates$MEK.$

Ac,vated$MEK$ac,vates$MAP'kinase.$

Ac,vated$MAP'kinase'moves$

to$nucleus$and$ac,vates$

transcrip,on$factors$that$

s,mulate$transcrip,on$of$

cell$cycle$genes.$

Cascade'of'reac-ons'

Types'of'cancer'causing'genes:'

Oncogenes$=$Mutated$dominantHac,ng$s#mulatory$genes$that$cause$cancer.$

(protoGoncogene'=$oncogene$prior$to$muta,on)$$

Tumor'suppressor'genes'=$Mutated$recessiveHac,ng$inhibitory$genes$that$cause$cancer.$

DNA'repair'genes'=$muta,ons$in$DNAHrepair$genes$can$

increase$the$likelihood$of$acquiring$muta,ons$in$these$

genes.$

Two$processes$that$control$rate$of$muta,ons$arising$in$cell:$

$1)$The$rate$that$muta,ons$arise$in$replica,on$and$aier.$

$2)$The$efficiency$with$which$errors$are$corrected.$

miRNAs'and'Cancer'A$source$of$cancer….$

A$poten,al$therapy$for$cancer…$

Cancer'Genome'Project'

Goal$is$to$completely$

sequence$the$genome$of$

500$tumors$in$50$different$

types$of$cancer.$$

Currently:$

71$genomes$complete$or$in$process.$

18$countries.$

Genome'mapping'using$Gene-c'Markers'

•  We$can$use$linkage"analysis"to$iden,fy$disease$loci.$

•  We$iden,fy$gene-c'markers$that$are$linked$to$(inherited$with)$disease.$

•  Gene-c'Marker'=$Any$gene$or$DNA'sequence'that$can$be$used$to$iden,fy$a$loca,on$in$the$genome.$

Single'Nucleo-de'Polymorphism'='SNP'Chromosomes$are$iden,cal$

for$most$of$their$lengths.$

SNPs$are$varia-ons$at$a$single"base.$

Each$set$of$SNPs$

='a'Haplotype'

Restric-on'enzymes$$(restric,on$endonuclease)$

$

•  Isolated$from$bacteria$(viral$defense).$

•  Cut$dsDNA$in$a$sequence4specific4way.$

•  usually$recogni-on'site$is$4$to$8bp$long.$

•  Most$recogni,on$sequences$are$palindromic.$$

Restric,on$enzymes$

make$two$kinds$of$cuts:$

1)'StaggeredG'or'“s-ckyG”'ends'

$

&$$

2)'Blunt'ends'

(palindromic)'

Gel'electrophoresis'

Used$to$separate$

nucleic$acids$based$

on$their$size.$

•  Nucleic$acids$are$‘loaded’$into$a$gel$

matrix$that$is$in$a$

salt$buffer.$

•  An$electrical$charge$is$passed$through$

the$gel.$

•  Nucleic$acids$will$travel$to$the$

posi-ve$pole.$

Wells$for$sample$loading.$

Gel'electrophoresis'

•  Something$is$added$to$DNA$

or$gel$that$allows$

visualiza,on$(e.g.$EtBr,$

radioac,ve$label).$

•  Sample$is$run$alongside$a$

known$size'standard'or$‘ladder’.$

•  Smaller$fragments$‘run’$

faster$than$larger$

fragments.$

(Wells)$

DNA'''''

Moves'''''

This'''''

Direc-on''

“Run to

red”

Big'

Small'

Restric-on'Fragment'Length'Polymorphism'(RFLP)'

Varia-on$in$Restric,on$enzyme$

recogni-on'sequences'results$in$heritable$differences$in$‘cut$

pa\erns’$between$individuals.$

Ancestral$Sequence$had$2$HaeIII$sites.$

Muta,on$(ie.$SNP)$results$in$some$people$having$

2$sites$and$some$people$having$one$site.$

When$treated$with$HaeIII,$each$varia,on$produces$a$different$‘banding’$pa\ern$when$evaluated$with$

Gel$electrophoresis.$

Restric-on'Fragment'Length'Polymorphism'(RFLP)'

RFLP’s'can'be'used'to'detect'linkage.'