1st March - Mechanisms of Tumour metastasis and angiogenesis Flashcards
Outline the architecture of a tissue
Epithelium Stem Cells Basement membrane Mesenchyme -Nerve -Blood vessels -Collagen -Fibroblasts -Muscle
Outline the metastatic cascade
- Clonal expansion, growth, differentiation and angiogenesis
- Metastatic subclone
- Adhesion to and invasion of the basement membrane
- Passage through ECM
- Intravasation
- Interaction with host lymphoid cells
- Tumour cell embolas
- Adhesion to the basement membrane
- Extravasation
- Metastatic deposit
- Angiogenesis
- Growth
What is intravasation?
Entering the blood vessel
What is extravasation?
Exiting the blood vessel
What is metastasis?
The escape of cancer cells from a primary site and their re-establishment at a distant site
What are the key molecular events that are required for metastasis to occur?
Changes in cell adhesion
Production of proteolytic enzymes
Change in the balance of positive and negative regulators of angiogenesis
What mediates homophilic cell:cell interactions?
E-cadherin
What mediates cell-substrate interaction?
Integrins
What mediates heterophilic cell-cell interactions?
Immunoglobulin super family and/or selectins
What are the proteolytic enzymes secreted by a transformed cell?
MMPs
uPA/uPAR system
What is the first process that must be undergone for a cell to escape its neighbours?
Epithelial to mesenchymal transition in which the polarised epithelial cell phenotype switches to a motile fibroblastoid or mesenchymal phenotype
What is a marker of whether the epithelial to mesenchymal transition has been undertaken?
Vimentin
Outline the cell-matrix interactions that must be lost during EMT
Focal contacts
Hemidesmosomes
What are focal contacts?
Integrins provide the link between ECM and actin cytoskeleton
What are hemidesmosomes?
Focal contacts can also link to intermediate filaments
Outline the cell-cell adhesions that must be lost during EMT
Adhesion belt
Tight junctions
Desmosome
Gap Junction
What is the adhesion belt?
Cytoplasm linked to the actin cytoskeleton using cadherins
What is a desmosome?
Cytoplasm linked to IFs through cadherins
What are the classic cadherins?
E-cadherin
N-cadherin
P-cadherin
VE-cadherin
What are the desmosomal cadherins?
Democollis
Demogleins
What is e-cadherin?
Epithelial cadherin
What are the junctional structures that normally connect epithelial cells through e-cadherin?
Tight junctions
Adherens junctions
Desmosomes
How does e-cadherin interact with the cytoskeleton?
Through alpha, beta and gamma catenins and p12 OCAS
Outline the structure of e-cadherin
Each module contains 5 cell adhesion domains The molecules dimerize, and form a lattice, a bit like a zipper
How does calcium affect the structure of e-cadherin?
In the absence of calcium the extracellular domain is floppy with calcium it is rigid and more able to form a dimer
What are the two roles of beta catenin?
Forming cell junctions with e-cadherin
TF role as part of the Wnt signalling pathway
How was the role of e-cadherin in metastasis established?
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
How was the causal role of e-cadherin in the adenoma to carcinoma transition established?
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
What indicated that e-cadherin loss of function was required for cancer?
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
What is the function of N-cadherin?
It promotes cell motility
What is the association of P and N cadherin with E cadherin?
Seems that a decrease in E-cadherin and an increase in P and N cadherin leads to EMT
