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Biología del cáncer

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MIN CIN Aneuploidía➔ Pérdida de p53, pRB, BRCA,

HNPCC

Mecanismos oncogénicos

Células cáncer

Proliferación desregulada

Pérdida de TSG (pRB, p53) Incremento oncogenes (Ras, Myc)

Inhabilidad para diferenciarse

Paro antes de diferenciación terminal Persisten funciones de células madres

Pérdida de la apoptosis

↓ p53 ↑ bcl2

Inestabilidad genómica

Pérdida de la senescencia replicativa

25-50 divisiones (pRB, p53, p16INK4) TELomerasa

Incremento angiogénesis

↑ VEGF, FGF, IL-8 ↓ TSG: endostatina,

trombospondinaInvasión

↓ gap junctions, cadherens ↑ MMP → Epithelial to mesenchymal

Evasión sistema inmune

↓ MHC I & II T-Cell tolerance / ↓ Dendrítica

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Growth factors

Nutrients & O2

Hormones

Cell-Cell inter.

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Inducción de p53 por daño de DNA y retenes oncogénicos

mdm2

p53

ATM/ATR

chk1 / chk2

mdm2 mdm2P19ARF

myc, E2F, EIA

Inducción P19ARF

p53 p53

p53 p53

Activación transcripcional de los genes respondedores a p53

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Extracellular Domain

Transmembrane Domain

Intracellular Domain

EGF Pathway

EGFR: transmembrane protein

Tyrosine Kinase Domain

Adapted from:Ciardiello F, et al. N Engl J Med. 2008;358:1160-1174. www.clinicaloptions.com

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HER/erbB family

Salomon DS, et al. Crit Rev Oncol Hematol 1995;19:183–232Woodburn JR. Pharmacol Ther 1999;82:241–50

HER1EGFRerbB1

HER2erbB2neu

EGFTGF-α

AmphiregulinBetacellulin

HB-EGFEpiregulin Heregulins

NRG2NRG3

HeregulinsBetacellulin

Cysteine-rich

domains

Tyrosine-kinase

domains

HER3erbB3 HER4

erbB4

Ligands:

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Y920Y891Y845

EGF

Stepwise EGFR ligand binding and tyrosine phosphorylation

1

Y1146Phosphotyrosine

EGF

TM

N

C

EGFR

TM

L1L2

CR2

CR1

N

C

monomers tethered, inactive

TM

N

C

TM

N

C

EGFRCR1

L2

CR2

L1

2 predimer extended, symmetric, inactive

EGF

TMTM

EGFRCR1

L2

CR2

L1

N

C

3 dimer extended, asymmetric

EGF

TM

EGFRCR1

L2

CR2

L1

N

C

4 dimer extended, asymmetric, active

EGF

5 dimer extended, asymmetric switched

EGFCR1

L2

CR2

L1

TM

N

C

TM

CNY845

Y920Y891

Y992 Y1045

Y1068

Y1086

Y1173Y1148 Y1148

Y1086

Y1173

Y1068Y1045Y992

EGFCR1

L2

CR2

L1

TM

N

C

TM

C

N

Y1148

Y1086

Y1173

Y1068Y1045Y992

Y845Y920Y891

Y1148Y1086

Y1173

Y1068

Y1045 Y992

Y891Y920Y845

6 dimer extended, asymmetric active

activated kinase

activating kinase

kinaseinactive

tethered,inactive

extended,active

kinaseinactive

receptor kinase

donor kinase activating kinase

activated kinase

receptor kinase

donor kinase

EGF

CN

EGF EGF

EGFR

TM

C

N

EGFR

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p27

E2F 1-3

KSR

Growth Factor signaling modulesCR1GF

L1

L2CR2

CR1

Y845 Kinase

Y1173

Y1086

Y891

Y992

Y1148

Y1045

Y920

Y1068

L1

L2CR2

Y845

Kin

ase

Y1173

Y1086

Y891

Y992

Y1148

Y1045

Y920

Y1068

GFCR1

PI3KPDK

aPKC

AP-1AP-1STAT 3P

STAT 3P

PP

Grb2SOS

Ras

SHC

Src STAT 3P

STAT 3P

STAT 3P

p70S6KP

P

SRFElk Ets

P

TCFCRE NFkBCRE

PP

NFkB

P P

MEK1/2ERK1/2S217 S221

T202

Raf1S338

Y34114-3-3

GSK-3

-Catenin

S9

Glycogensyntahse

CRMP-2

WNK-1P

P

P

P

APCP

MAP1BP

PKBT308 S473

BadPCas 9P

XIAPP

P

PFK-2

ATP-citratelyase

PKCP

PKCP

PKCP

PLC1

p90Rsk

MEKK2JNK1/2

MKK7MKK4

PP

Grb2

SOS

Rac/Rho

PP

DAG

IP3

PKC

RKIPS153 I-1

P

PP1

MARCKS

Ca Ca

Ca Ca

Ca

Ca

Ca

Ca

CaCaM

CamKIICaM MLCKCaM P

DAPKCaM P

P

FascinP

P

S129

Bcl-2G1

S

G2M

mTORP Raptor

GL FKBP12

4EBP1P

S6

p70S6KP

P

AAAAA60S

40S

PTEN

P

P

CotP

FOXO1

Foxa2

P

P

P

C-MycE2F 1-3

ATM

Cyclin D1

CDK4/6

pRb

HDM2P

p53 P

GRK5CaM

FOXO1

P P

P

P

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YOUR LOGOProliferationApoptosis Resistance Transcription

TGFα Interleukin-8 bFGF VEGF

MetastasisAngiogenesis

Shc

PI3K

RafMEKK-1

MEKMKK-7

JNK ERK

Ras

mTOR

Grb2

AKT

Sos-1

EGF Pathway

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Angiogenesis is the process of new blood vessel formation from existing vasculature

Sturk, Dumont. In: Basic Science of Oncology 2005

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Angiogenesis is essential to tumor development

An independent blood supply is required for a tumor to grow beyond 2mm in diameter1,2

Larger tumors rely on their vasculature for survival and further growth1,2

1. Ferrara, Henzel. Biochem Biophys Res Commun 1989; 2. Folkman. NEJM 1971

Small avascular tumorTumor

Blood vessels

Large, highlyvascularized tumor

Growthfactors

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Angiogenesis is involved throughout tumor formation, growth and metastasis

Stages at which angiogenesis plays a role in tumor progression

Premalignant

stage

Malignant

tumor

Tumorgrowt

h

Vascular

invasion

Dormantmicrometastasi

s

Overtmetastasi

s(Avascula

rtumor)

(Angiogenic

switch)

(Vascularized

tumor)

(Tumor cellintravasation

)

(Seeding indistant organs)

(Secondaryangiogenesis

)

Adapted from Poon, et al. JCO 2001

Tumour growth depends on angiogenesis

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Also known as vascular permeability factor (VPF)

aka: VEGF-A; related molecules are VEGF-B, C, and D

Central mediator of angiogenesis

Mitogen for endothelial cells

45KDa heparin binding homodimeric glycoprotein

Regulates angiogenesis

Promotes survival of immature vasculature

Binds to membrane receptor tyrosine kinases

Four molecular species arising from the same gene- VEGF121, VEGF165*, VEGF189, VEGF206

*Predominant molecular species

VEGF is at the center of the angiogenic pathway

1. Ferrara, et al. Biochem Biophys Res Comm 19892. Leung, et al. Science 1989; 3. Keck, et al. Science 1989

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The VEGF family of isotypes and receptors

Angiogenesis Lymphangiogenesis

VEGF-A, -B, PlGF

VEGFR-1 VEGFR-2

VEGF-A, -C, -D

VEGFR-3

VEGF-C, D

Disulfide bonds

Adapted from Hicklin, Ellis. JCO 2005

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Tumor vasculature is abnormal

Konerding et al. Blood Perfusion and Microenvironment of Human Tumors 2002

Normal colon Nearby colorectal cancer

Tumor vasculature is dilated, highly chaotic, and tortuous, with a lack of hierarchical vessel arrangement

VEGF INDEPENDENT.

VEGF DEPENDENT.

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Telomeres

Ends of linear chromosomes

Centromere

TelomereTelomere

Repetitive DNA sequence(TTAGGG in vertebrates)

Specialized proteins

Form a 'capped' end structure

Telomeres 'cap' chromosome ends

TELOMERE STRUCTURE

5’ 3’

5'

3'

Telomerict loop

Telomericproteins:

TRF1TRF2TIN2RAP1

TANKS 1,2POT1

etc

NUCLEARMATRIX

Why are telomeres important?

Telomeres allow cells to distinguish chromosomesends from broken DNA

Stop cell cycle!Repair or die!! Homologous recombination

(error free, but need nearby homologue)

Non-homologous end joining(any time, but error-prone)

Why are telomeres important?Prevent chromosome fusions by NHEJ (non-homologous end joining)

NHEJ

Mitosis

FUSIONBRIDGE

BREAKAGE

Fusion-bridge-breakage cycles

Genomic instability

Cell death OR neoplastic transformation

Telomere also provide a means for "counting" cell division

Pro

lifer

ativ

e ca

paci

ty

Number of cell divisions

FiniteReplicativeLife Span"Mortal"

InfiniteReplicativeLife Span"Immortal"

How do cells "know" how many divisions they have completed??

The End Replication Problem:Telomeres shorten with each S phase

OriDNA replication is bidirectionalPolymerases move 5' to 3'Requires a labile primer

3'5'

3'5'

5'

5' 3'3' 5'

Each round of DNAreplication leaves

50-200 bp DNA unreplicatedat the 3' end

Telo

mer

e Le

ngth

(hu

man

s)

Number of Doublings

20

10

Cellular (Replicative) Senescence

Normal Somatic Cells

(Telomerase Negative)

Telomere also provide a means for "counting" cell division: telomeres shorten with each cycle

Telomeres shorten from 10-15 kb(germ line) to 3-5 kb after 50-60 doublings

(average lengths of TRFs)

Cellular senescence is triggered whencells acquire one or a few critically short telomeres.

How do replicatively immortal cells

avoid complete loss of telomeres

(how do they solve the end-replication problem)?

TELOMERASE:Key to replicative immortality

Enzyme (reverse transcriptase) with RNA and protein components

Adds telomeric repeat DNA directly to 3' overhang (uses its own RNA as a template)

Vertebrate repeat DNA on 3' end:TTAGGG

Telomerase RNA template:AAUCCC

TELOMERASE:Key to replicative immortality

+ TELOMERASE

Overcomes telomere shortening and the end-replication problem

Expressed by germ cells, early embryonic cells

Not expressed by most somatic cells (human)

May be expressed by some stem cells, but highly controlled

Expressed by 80-90% of cancer cellsRemaining still need to overcome the end replication problem;

do so by recombinational mechanisms -- ALT (alternative lengthening of telomeres) mechanisms

Telo

mer

e Le

ngth

(hu

man

s)

Number of Doublings

20

10

Cellular (Replicative) Senescence

Normal Somatic Cells

(Telomerase Negative)

Germ Cells (Telomerase Positive)

+ Telomerase

Telomere Length and Cell Division Potential

HOWEVER,

CELLS THAT EXPRESS TELOMERASE

STILL UNDERGO SENESCENCE

(E.G., IN RESPONSE TO DNA DAMAGE, ONCOGENES, ETC.)

Inducers of cellular senescenceCell proliferation(short telomeres)

DNA damage OncogenesStrong mitogens/

stress

Potential Cancer Causing Events

Telomerase:Biomedical uses

Expand cells for replacement therapies(burns, joint replacements, etc)

Telomerase inhibitors to selectively kill cancer cells

The telomere hypothesis of aging

Telomeres shorten with each cell division and therefore with age

TRUE

Short telomeres cause cell senescence andsenescent cells may contribute to aging

TRUE

HYPOTHESIS:Telomere shortening causes aging and

telomerase will prevent agingTRUE OR FALSE?

The telomere hypothesis of aging

Telomere length is not related to life span(mice vs human; M musculus vs M spretus)

Telomeres contribute to aging ONLY if senescent cells contribute to aging

Telomerase protects against replicativesenescence but not senescence induce by

other causes

SUMMARY

Telomeres are essential for chromosome stability

Telomere shortening occurs owing to the biochemistry ofDNA replication

Short telomeres cause replicative senescence (other senescence causes are telomere-independent)

Telomerase prevents telomere shortening andreplicative senescence

The telomere hypothesis of aging depends on the cellular senescence hypothesis of aging