1st March - Mechanisms of Tumour metastasis and angiogenesis

Question 1

Outline the architecture of a tissue

Answer 1

Epithelium
Stem Cells
Basement membrane
Mesenchyme
-Nerve
-Blood vessels
-Collagen
-Fibroblasts
-Muscle

Question 2

Outline the metastatic cascade

Answer 2

1. Clonal expansion, growth, differentiation and angiogenesis
2. Metastatic subclone
3. Adhesion to and invasion of the basement membrane
4. Passage through ECM
5. Intravasation
6. Interaction with host lymphoid cells
7. Tumour cell embolas
8. Adhesion to the basement membrane
9. Extravasation
10. Metastatic deposit
11. Angiogenesis
12. Growth

Question 3

What is intravasation?

Answer 3

Entering the blood vessel

Question 4

What is extravasation?

Answer 4

Exiting the blood vessel

Question 5

What is metastasis?

Answer 5

The escape of cancer cells from a primary site and their re-establishment at a distant site

Question 6

What are the key molecular events that are required for metastasis to occur?

Answer 6

Changes in cell adhesion
Production of proteolytic enzymes
Change in the balance of positive and negative regulators of angiogenesis

Question 7

What mediates homophilic cell:cell interactions?

Answer 7

E-cadherin

Question 8

What mediates cell-substrate interaction?

Answer 8

Integrins

Question 9

What mediates heterophilic cell-cell interactions?

Answer 9

Immunoglobulin super family and/or selectins

Question 10

What are the proteolytic enzymes secreted by a transformed cell?

Answer 10

MMPs

uPA/uPAR system

Question 11

What is the first process that must be undergone for a cell to escape its neighbours?

Answer 11

Epithelial to mesenchymal transition in which the polarised epithelial cell phenotype switches to a motile fibroblastoid or mesenchymal phenotype

Question 12

What is a marker of whether the epithelial to mesenchymal transition has been undertaken?

Answer 12

Vimentin

Question 13

Outline the cell-matrix interactions that must be lost during EMT

Answer 13

Focal contacts

Hemidesmosomes

Question 14

What are focal contacts?

Answer 14

Integrins provide the link between ECM and actin cytoskeleton

Question 15

What are hemidesmosomes?

Answer 15

Focal contacts can also link to intermediate filaments

Question 16

Outline the cell-cell adhesions that must be lost during EMT

Answer 16

Adhesion belt
Tight junctions
Desmosome
Gap Junction

Question 17

What is the adhesion belt?

Answer 17

Cytoplasm linked to the actin cytoskeleton using cadherins

Question 18

What is a desmosome?

Answer 18

Cytoplasm linked to IFs through cadherins

Question 19

What are the classic cadherins?

Answer 19

E-cadherin
N-cadherin
P-cadherin
VE-cadherin

Question 20

What are the desmosomal cadherins?

Answer 20

Democollis

Demogleins

Question 21

What is e-cadherin?

Answer 21

Epithelial cadherin

Question 22

What are the junctional structures that normally connect epithelial cells through e-cadherin?

Answer 22

Tight junctions
Adherens junctions
Desmosomes

Question 23

How does e-cadherin interact with the cytoskeleton?

Answer 23

Through alpha, beta and gamma catenins and p12 OCAS

Question 24

Outline the structure of e-cadherin

Answer 24

Each module contains 5 cell adhesion domains
The molecules dimerize, and form a lattice, a bit like a zipper

Question 25

How does calcium affect the structure of e-cadherin?

Answer 25

In the absence of calcium the extracellular domain is floppy with calcium it is rigid and more able to form a dimer

Question 26

What are the two roles of beta catenin?

Answer 26

Forming cell junctions with e-cadherin

TF role as part of the Wnt signalling pathway

Question 27

How was the role of e-cadherin in metastasis established?

Answer 27

Differentiated kidney epithelial cells became fibroblastic and invasive when treated with mAb to E-cadherin.
Loss of e-cadherin expression in breast cancer correlates with markers of metastasis
Exogenous expression of E-cadherin in MDA MB2331 breast carcinoma cells result in reduced bone marrow metastasis
Immunochemical studies - reduced E-cadherin expression in malignant disease

–> E-cadherin is involved in metastasis

Question 28

How was the causal role of e-cadherin in the adenoma to carcinoma transition established?

Answer 28

Mouse model of pancreatic beta cell carcinogenesis (perl 1998)
-RIP-Tag mice express SV40 T-antigen in beta cells under control of the rat insulin promoter
-Mice develop tumours in a multi-stage pathway: Islet cell hyperplasia –> angiogenesis –> solid beta cell tumour
-Nomral cells and adenoma expressed E-cadherin
-Carcinoma did not express E-cadherin
RIP-Tag mice x E-cadherin maintained mice –> E+ cad - tumour progression blocked at benign adenoma
-RIP-Tag mice x E-cadherin KO –> D/N Cad - Early invasion and metastasis

Question 29

What indicated that e-cadherin loss of function was required for cancer?

Answer 29

Germline mutation in familial gastric cancers
Change in expression of proteins in the adhesion complex w/ E-cadherin abrogates adhesion function
RTKs phosphorylate Beta catenin –> dissociation from the cadherin complex

Question 30

What is the function of N-cadherin?

Answer 30

It promotes cell motility

Question 31

What is the association of P and N cadherin with E cadherin?

Answer 31

Seems that a decrease in E-cadherin and an increase in P and N cadherin leads to EMT