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Chapter 20
Cell biology 2014 (updated 18/2, 4/7 -13 & 1/1 -14)
Lecture 12:
1205-1265
Cancer: latin word for crayfish
Will develop cancer
Will die of cancer
Cell Biology interactive  media  ”video” or ”interactive”
1
Basic tumor nomenclature
Benign 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
Different views on cancer biology
Old fasion view
Autonomous
cancer cells
3
A heterotypic cell biology view
Immune cells
Non-autonomous
heterogeneous
cancer cells
Other cells
Endothelial cells
In vitro propagated cell lines can only rarely be established from
tumor biopsies  tumor cells depends on their specific surrounding
Tumor progression
4
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
Definitions: oncogenes and tumor suppressors
An oncogene is a gene that when mutated, or
overexpressed, contributes to converting a normal cell into
a tumor cell (constitutive activity dominant phenotype)
Ras
point mutation
Bcl-2
overexpression
A tumor suppressor-gene is a gene whose loss, or
inactivation, contributes to converting a normal cell into
a tumor cell (recessive phenotype)
CKI
p53
Rb
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 makes
cancer development statistically improbable
Tumors acquire the capability to rapidly accumulate
genetic changes by e.g., the following mechanisms:
1. Microsatellite INstability (MIN): Point mutations
Common causes: defective DNA mismatch repair genes
2. Chromosomal INstability (CIN): Aneuploidy
Common causes: aberrant centrosome numbers
defective spindle regulatory proteins
defective checkpoint control
3. Chromosome breaks and translocations
Common causes: eroded telomeres
DNA breaks
6
Common cause of gene loss and amplification
DNA
strand
break
DNA
End
duplication fusion
Chromosome separation,
novel breaks
Gene loss
DNA break
Telomere
Gene amplification
7
The six hallmarks of cancer – A cell biology perspective
1. Self-sufficiency in proliferative signals
2. Insensitivity to anti-growth signals
3. Evading cell death (apoptosis)
4. Limitless replicative potential
5. Sustained angiogenesis
6. Metastasis capability
Make new
blood vessel!
8
Adopted from Hanahan & Weinberg, Cell 2000
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
Only one protein per pathway needs to be changed!
For example, a single protein in a mitogenic signaling pathway:
myc
G1
myc
G1
Even if two tumors would belong to the same diagnostic group,
they still have a unique combination of genetic alterations
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The retinoblastoma pathway
1. Self-sufficiency in proliferative signals
Mitogenic signaling (growth promoting signals)
Cdk
G1
Rb
E2F
Production of DNA
replisome components
Production of
S cyclin
Cdk
S
Initiation of
replication
P
Cdc6
P
ORC
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1. Cell type specific mitogenic pathways
Cells from different tissues express distinct sets of
growth factor receptors and signaling proteins
Cell type B
Cell type C
Cell type A
Major mitogen
signaling pathway: RTK
Alterations
in tumors:
Wnt
Hedgehog
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RTK signaling Wnt signaling Hedgehog signaling
12
1. Aberrant proliferative signals in tumors
Wnt
XGF
RTK
Ras
Hedgehog
Frizzled
Patched
Dishevelled
Smoothened
Raf
GSK-3b
Erk
b-catenin
myc
G1
myc
Fused
Axin
SuFu
G1
Gli
Gli
myc
G1
2. Insensitivity to anti-growth signals
The retinoblastoma pathway
Mitogen signaling
p15
p21
Cdk
G1
TGF-b
p16
HPV E7 viral
Rb
E2F
Cdk
P
Cdc6
P
ORC
S
13
3. Evading cell death (apoptosis)
Survival factor signaling
BH3
only
p53
Ligand
Death
receptor
Adaptor
Bcl-2
Bax
Cyt. C
Caspase 9
Caspase 8
Caspase 3
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Apoptosis
3. Survival factor signaling
PI-3 K
or
GPCR
or
RTK
P
3
P
P
PTEN
3 P
P
PKB/Akt
G1
+
elF4E
Bad
15
Cell growth
Apoptosis
4. Limitless replicative potential
Telomeres: stretches of repetitive DNA at the chromosome ends
that can form a protective loop structure
5´
3´
5´
3´
Complementarity due to the
repetitive sequence
5´ -GGGTTAGGGTTAGGGTTA G G
3´ -CCCAATCC
Chromosome lacking
telomeres will trigger
a p53 dependent cell
cycle block
G
AUCCCAAU
T
T
A
Telomerase, usually
not expressed in
somatic cells
To maintain telomere length tumor cells can re-start expression
of telomerase. An alternative mechanism employs enzymes
16
that are involved in DNA recombination
Make new
blood vessel!
5. Sustained angiogenesis
Blood
vessel
< 100 mm
Diffusion of O2
and nutrients
Endothelial cell
Too long
I am suffocating!
Let’s express VEGF
Anim. 23.7-angiogenesis
VEGF: Vascular endothelial
growth factor
17
5. Vascular Endothelial Growth Factor - VEGF
Ras
1. Constitutively
produced
in all tissues
4. Ras dependent signaling
can increase expression
levels of HIF-1
VEGF
HIF-1
VEGF gene
2. Constitutively
degraded via
pVHL, unless…
3. …hypoxia
(low O2)
pVHL
HIF-1
HIF-1: Hypoxia induced factor
pVHL: von Hippel–Lindau syndrome (hereditary cancer) is
caused by a germline mutation in the VHL gene
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Proteosome
5. Angiogenic factors affecting endothelial cells
Activators
VEGF
Inhibitors
Thrombospondin-1
p53
p53
Loss of p53
loss of
angiogenisis inhibition
Tumor with active p53
No angiogenesis
Tumor without active p53
Angiogenesis
19
5. Summary: regulation of angiogenesis
Ras
pVHL
Avastin
HIF-1
VEGF
p53
Thrombospondin-1
Angiogenesis
20
6. Metastasis capability
Metastasis, the ability of cancer cells to migrate, results from
multiple mutation events
1.
Basal
lamina
40-120 nm
2.
3.
4.
1. Loss of cell-cell adhesion
2. Loss of hemidesmosomes
3. Proteolytic degradation of the ECM
4. Migration through the ECM
21
6. Example of loss of cell-cell adhesion
Loss of E-cadherin is an important step in generating daughter
tumors (metastasis) in carcinomas
Malignant tumor
Benign tumor
Tumor
progression
Loss of E-cadherin
decreased cell adhesion
Migration, resettlement
and further proliferation
22
Metastasis
6. Penetration of basal lamina
Collagen IV fibril
1.
2.
3.
Laminin
Reprogramming / de-differentiation of cells:
1. Loss of hemidesmosomes/laminin receptor (integrin)
2. Expression of collagenase
3. Cytoskeletal changes
 Epithelial–mesenchymal transition (EMT)
23
Cell secretes proteases to clear
a path through the ECM
Blood vessel
6. Making it through the connective tissue
24
6. Sites of metastasis – blood flow
25
• Blood flow pattern determine the metastasis pattern in most
case (~70%)
Capillary of
the lung
Tumor cell entering
the blood system
Lung metastasis
Stomach or intestinal
tumor cell entering
the blood system
Capillary of
the liver
Liver metastasis
6. Sites of metastasis – microenvironment
• ”Seed-soil” pattern determine the metastasis pattern in other
cases (~30%)
Capillary of
the lung
Prostate tumor
cell entering
the blood system
Adjacent bone cells
produce specific
factors needed for
tumor cell growth
Capillary of
a bone
No lung metastasis
due to nonfavorable ”climate”
X X
26
Tumor progression: Familial adenomatous polyposis
Alberts et al. Fig. 20-46
2.
3.
X
X
X
X
X
5.
X
X XX X
1.
X
X
4.
6.
1. Self-sufficiency in
proliferative signals
2. Insensitivity to
Anti-growth signals
3. Evading cell death
4. Limitless replicative potential
5. Sustained angiogenesis
27
6. Metastasis capability
Step I. Starting point of familial adenomatous polyposis
By chance loss of the intact APC allele!
APC
APC
Wnt
GSK-3b
Axin
b-catenin
MMP7
G1
Chromosomal instability
Self-sufficiency in
proliferative signals
Metastasis
capability
Note dual action of APC: Hallmarks 1 & 6
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Step II. Progression of colon carcinoma
Loss of SMAD4
Oncogenic mutation in RAS
TGF - b
XGF
Smad 4
Ras
p15
G1
VEGF
Insensitivity to
anti-growth signals
Self-sufficiency in
proliferative signals
Sustained
angiogenesis
Hallmarks 1, 2 & 5
29
Step III. Progression of colon carcinoma
DNA damage
Loss of p53
Aberrant/incomplete
proliferation signals
p21
p53
Bax
Insensitivity to
anti-growth signals
PUMA
Bcl-2
Evading cell death
Hallmarks 2, 3 & 5
Thrombospondin-1
Sustained
angiogenesis
30
Step IV. Progression of colon carcinoma
Expression of telomerase
Loss of E-CADHERIN
AUCCCAAU
Limitless replicative
potential
Metastasis
capability
The End
Hallmarks 4 & 6
31
Fulfilling the hallmarks of cancer in colon cancer
1. Self-sufficiency in proliferative signals
2. Insensitivity to anti-growth signals
3. Evading cell death (apoptosis)
4. Limitless replicative potential
5. Sustained angiogenesis
6. Metastasis capability
Ras
APC
APC
Smad 4
Ras
p53
p53
AUCCCAAU
Telomerase
p53
E cadherin
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
33
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
35
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).
36
Decision tree: breast cancer treatment at NUS
T: clinical/mammographic evaluation
N: regional lymph nodes
M: distant metastases
Non-specific
Mix of cytostatic drugs, e.g., FEC
(5-FU, epirubicin, cyklofosfamid)
or SBG 2000-1 mix
Irradiation therapy
Specific
TAM: Tamoxifen (anti-estrogen)
A temporary cure!
(3-60 (?) years)
37
Future goals of (molecular) diagnostics
•
•
•
•
Early detection
Accurate prognosis
Good prediction (of therapy response)
Reveal molecular therapy targets
38