tumor biology

Lecture 12:

Cancer: latin word for crayfish

Will develop cancer Will die of cancer

Optional!Chapter 201205-1265

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Cell Biology interactive media ”video” or ”interactive”

Cell biology 2014 (updated 18/2, 4/7 -13 & 1/1 -14)

Basic tumor nomenclatureBenign tumor Malignant tumor = cancer

Metastasis forming cell(primary killer)

Carcinoma: derived from epithelial cells (90% of all cancers)

Sarcoma: derived from connective or muscle tissue

Leukemia: derived from hematopoietic cells (BM and blood)

Lymphoma: derived from lymphocytes (lymph nods) 2

Autonomouscancer cells

Old fasion view

Endothelial cells

A heterotypic cell biology viewImmune cells

Other cells

Non-autonomousheterogeneouscancer cells

Different views on cancer biology

In vitro propagated cell lines can only rarely be established from tumor biopsies tumor cells depends on their specific surrounding

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Tumor progression

A malignant tumor does not arise from a single genetic change;many changes are required to produce a life threatening cancer

Tumor progression is defined as the acquisition of permanent changes in characteristics of selected subpopulations of the tumor

Progenitors of the same clone, but still a heterogeneous tumor

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Definitions: oncogenes and tumor suppressors

Ras

p53Rb

An oncogene is a gene that when mutated, or overexpressed, contributes to converting a normal cell intoa tumor cell (constitutive activity dominant phenotype)

A tumor suppressor-gene is a gene whose loss, or inactivation, contributes to converting a normal cell into a tumor cell (recessive phenotype)

Bcl-2

CKI

point mutation overexpression

Inactivating point mutations or loss of the entire gene(germ line mutation in one allele and/or acquired somatic mutations) 5

The normal stability of the genome makescancer development statistically improbable

1. Microsatellite INstability (MIN): Point mutationsCommon causes: defective DNA mismatch repair genes

2. Chromosomal INstability (CIN): AneuploidyCommon causes: aberrant centrosome numbers

defective spindle regulatory proteinsdefective checkpoint control

3. Chromosome breaks and translocations Common causes: eroded telomeres

DNA breaks

Tumors acquire the capability to rapidly accumulate genetic changes by e.g., the following mechanisms:

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Common cause of gene loss and amplification

DNA strand break

DNA duplication

End fusion

Chromosome separation, novel breaks

Gene loss

Gene amplificationTelomereDNA break

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1. Self-sufficiency in proliferative signals

3. Evading cell death (apoptosis)

2. Insensitivity to anti-growth signals

4. Limitless replicative potential

5. Sustained angiogenesis

6. Metastasis capability

Make new blood vessel!

Adopted from Hanahan & Weinberg, Cell 2000

The six hallmarks of cancer – A cell biology perspective

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Tumor progression - molecular mechanisms• To be able to turn into a malignant tumor, each of the six hallmarks has to be fulfilled • This is done by changing the level/activity of various proteins

G1 G1

Only one protein per pathway needs to be changed!

For example, a single protein in a mitogenic signaling pathway:

Even if two tumors would belong to the same diagnostic group, they still have a unique combination of genetic alterations 9

myc myc

Cdk G1

Cdk S

Rb

DNAreplisome

ORCCdc6P

P DNAreplisome

Mcm

Mitogenic signaling (growth promoting signals)

E2F

Production of DNA replisome components

Production ofS cyclin

Initiation of replication

1. Self-sufficiency in proliferative signals Th

e re

tinob

last

oma

path

way

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1. Cell type specific mitogenic pathways

Cell type A Cell type B Cell type C

RTK Wnt Hedgehog

Cells from different tissues express distinct sets of growth factor receptors and signaling proteins

Alterationsin tumors: RTK signaling Wnt signaling Hedgehog signaling

Major mitogensignaling pathway:

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G1

myc

Ras

Raf

Erk

XGF Wnt

Dishevelled

b-catenin

G1 myc

Frizzled

G1 myc

RTK

Gli

Fused

Patched

Smoothened

Gli

SuFu

Hedgehog

GSK-3b AxinAPC

1. Aberrant proliferative signals in tumors 12

The

retin

obla

stom

a pa

thw

ay

Cdk G1

Cdk S

Rb

DNAreplisome ORC

Cdc6PP

p15Mitogen signaling

E2F

HPV E7

p21p16


TGF-b

viral

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Survival factor signaling

Caspase 9 Caspase 3

Apoptosis

BH3only

Caspase 8

Adaptor

Deathreceptor

Ligand

BaxBcl-2


p53

Cyt. C

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PI-3 K

3. Survival factor signaling

P3 3

PTENP

PP

P

PKB/Akt

Bad

Apoptosis

elF4E

Cell growth

GPCR or RTK

or

+

G1

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Telomerase, usuallynot expressed insomatic cells

-GGGTTAGGGTTAGGGTTA

-CCCAATCC

5´

AUCCCAAU

G GG T T A

3´

3´5´

Complementarity due to therepetitive sequence

3´5´

Chromosome lackingtelomeres will trigger a p53 dependent cellcycle block

Telomeres: stretches of repetitive DNA at the chromosome ends that can form a protective loop structure


To maintain telomere length tumor cells can re-start expression of telomerase. An alternative mechanism employs enzymesthat are involved in DNA recombination 16


Blood vessel

Endothelial cell< 100 mm

Too longDiffusion of O2 and nutrients

I am suffocating!Let’s express VEGF

Make new blood vessel!

VEGF: Vascular endothelialgrowth factor

17Anim. 23.7-angiogenesis

5. Vascular Endothelial Growth Factor - VEGF

VEGF gene

VEGFHIF-1

HIF-1Ub

UbUb

pVHL

Constitutively produced

in all tissues

…hypoxia (low O2)

Constitutively degraded via

pVHL, unless…

Proteosome

Ras

1.

2.

3.

4. Ras dependent signaling can increase expressionlevels of HIF-1

HIF-1: Hypoxia induced factorpVHL: von Hippel–Lindau syndrome (hereditary cancer) is caused by a germline mutation in the VHL gene

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5. Angiogenic factors affecting endothelial cellsActivators Inhibitors

VEGF Thrombospondin-1

Loss of p53 loss of angiogenisis inhibition

p53p53

Tumor with active p53

No angiogenesis

Tumor without active p53

Angiogenesis 19

5. Summary: regulation of angiogenesis

Thrombo-spondin-1VEGF

HIF-1 p53pVHL

Angiogenesis

Ras

Avastinä

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1.

2.3.

1.

2.3.

Loss of cell-cell adhesion

Loss of hemidesmosomes

Proteolytic degradation of the ECM

Metastasis, the ability of cancer cells to migrate, results frommultiple mutation events

4.

4. Migration through the ECM

40-120 nmBasal lamina


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Loss of E-cadherin is an important step in generating daughter tumors (metastasis) in carcinomas

6. Example of loss of cell-cell adhesion

Benign tumor Malignant tumor

Loss of E-cadherin decreased cell adhesion

Metastasis

Migration, resettlement and further proliferation

Tumor progression

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6. Penetration of basal lamina

Collagen IV fibril

Laminin

1.

2.

3.

1. 2. 3.

Loss of hemidesmosomes/laminin receptor (integrin)

Expression of collagenase

Cytoskeletal changes Epithelial–mesenchymal transition (EMT) 23

Reprogramming / de-differentiation of cells:

6. Making it through the connective tissue

Cell secretes proteases to clear a path through the ECM

Blo

od v

esse

l

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6. Sites of metastasis – blood flow

Tumor cell entering the blood system

Capillary of the lung

Lung metastasis

Capillary of the liver

Liver metastasis

Stomach or intestinal tumor cell entering the blood system

• Blood flow pattern determine the metastasis pattern in most case (~70%)

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6. Sites of metastasis – microenvironment

Capillary of the lung

No lung metastasisdue to non-

favorable ”climate”

• ”Seed-soil” pattern determine the metastasis pattern in other cases (~30%)

X X

Prostate tumor cell entering the blood system

Capillary of a bone

Adjacent bone cells produce specific factors needed fortumor cell growth

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Tumor progression: Familial adenomatous polyposis

X XX X

X X

X X

1.

2. 3.

4. 6.

5.X X

X X

1.

2.

3.

4.

6.5.

Self-sufficiency in proliferative signals Insensitivity to Anti-growth signalsEvading cell death Sustained angiogenesis

Metastasis capability

Limitless replicative potential

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Alberts et al. Fig. 20-46

Note dual action of APC: Hallmarks 1 & 6

By chance loss of the intact APC allele!

G1

Wnt

b-catenin

Self-sufficiency inproliferative signals

Chromosomal instability Metastasis capability

MMP7

AP

C

Step I. Starting point of familial adenomatous polyposis

APC

GSK-3b AxinAPC

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VEGF

Ras

Oncogenic mutation in RAS

G1

XGF

Self-sufficiency inproliferative signals

Sustained angiogenesis

p15

Smad 4

Insensitivity toanti-growth signals

Loss of SMAD4

TGF b-

Step II. Progression of colon carcinoma

Hallmarks 1, 2 & 5 29

p53

p21

Insensitivity toanti-growth signals

Loss of p53

Sustained angiogenesis

PUMA BaxThrombo-spondin-1

Aberrant/incomplete proliferation signals

DNA damage

Evading cell death

Bcl-2

Step III. Progression of colon carcinoma

Hallmarks 2, 3 & 5 30

AUCCCAAU

Limitless replicativepotential

Expression of telomerase Loss of E-CADHERIN

Metastasis capability

The End

Step IV. Progression of colon carcinoma

Hallmarks 4 & 6 31

Fulfilling the hallmarks of cancer in colon cancer

1. Self-sufficiency in proliferative signals






AUCCCAAU Telomerase

p53

p53

p53Smad 4

Ras

Ras

E cadherin

APC

APC

Fulfilling hallmarks 1 – 6 within a life time depends on genomic instability 32

Breast cancer in Sweden

• 6,623 new cases in 2002 (early onset)• Incidence/year ~115 per 100,000

Mortality/year ~ 35 per 100,000

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The TNM system for clinical staging

Tumor/ Node/ Metastasis:• T, clinical/mammographic

evaluation of tumor (0-4).• N, clinical evaluation of regional

lymph nodes (0-3).• M, distant metastases (0, 1).

• Stage 0: Tis N0 M0

Stage I: T1 N0 M0

Stage 2: T1-3 N1 M0

Stage 3: T1-4 N1-3 M0

Stage 4: T1-4 N1-3 M1 (is: in situ well encapsulated)

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Stage and prognosis

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Routine prognostic and predictive factors

• TNM (Tumor/Node/Metastasis)• Histologic type and grade (as judge by the

appearance under the microscope)• Molecular markers: Ki-67, estrogen and

progesteron receptors, and ERBB2 (EGF receptor).

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Decision tree: breast cancer treatment at NUST: clinical/mammographic evaluationN: regional lymph nodesM: distant metastases

Non-specificMix of cytostatic drugs, e.g., FEC (5-FU, epirubicin, cyklofosfamid)or SBG 2000-1 mixIrradiation therapy

SpecificTAM: Tamoxifen (anti-estrogen)A temporary cure!(3-60 (?) years)

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Future goals of (molecular) diagnostics

• Early detection• Accurate prognosis• Good prediction (of therapy response)• Reveal molecular therapy targets

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tumor biology

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