Lecture 20: Metastasis - Epithelial organisation and regulation

Question 1

What can prevent metastasis into new tissue sites?

Answer 1

1. Tissue archeticture: connective tissue, basement membrane, junctions
2. Blood vessel structure: basement membrane,

Question 2

How do cells migrate and invade?

Answer 2

Epithelial to mesenchymal transition (EMT)

Question 3

What are the classifications of EMT?

Answer 3

Type 1: embryonic development
Type 2: Wound healing and tissue regeneration in adult tissues
Type 3: cancer

Question 4

What are the features of EMT cells

Answer 4

Spindle-shaped
Anterior-posterior polarisation
Weak cell:cell adhesion
Atered cell:ECM adhesion

=

Strong potential for migration
Invasive - production of enzyme which degrade ECM (proteases)

Question 5

How is EMT induced?

Answer 5

Multiple signals required for initiation and maintaining EMT

Req signals from epithelial (cancer) and stromal cells

Hepatocyte GF (ligand) - Met (receptor) pathway
^^^ HGF SIGNALLING
1. produced by a variety of stromal cells
2. Receptor Met found on epithelial cells
3. HGF capable of produced many of EMT associated changes

Question 6

How is EMT coordinated?

Answer 6

Small number of transcription factors that work in combinations, often inducing the expression of each other

TF e.gs.,
Snail
Slug
Twist
etc

Question 7

What is the evidence for Twist’s role in metastasis

Answer 7

Promotes metastasis but not primary tumour growth

Spontaneous metastasis assay:
1. injected highly metastatic breast cancer cells to mammary fat pad
2. siRNA was used to KO Twist expression
3. Reduction in metastasis but no change in tumour growth

Question 8

What is the role of E-cadherin in signalling pathways?

Answer 8

Oncogenic signalling pathways for: migration, invasion, proliferation

EMT state = loss of E-cadherin

Wnt pathway
1. Regulates cell migration and proliferation
2. Associated with several cancers: GI, breast, melanoma

Other pathways
1. EGFR
2. c-Met
3. PI3K/AKT
4. Rho GTPase
5. Ras
6. Rac
7. MAPK
8. HIPPO

Question 9

What is the importance of the E to N-cadherin switch?

Answer 9

N-cadherin increases cancer cell affinity to surrounding stromal cells normally displaying N-cadherin

melanoma cells: N-chaderin
1. bind to fibroblasts and endothelial cells
2. Facilitates invasion into dermal stroma

Loss of E-cadherin leads to more invasive and malignant phenotype

Evidence: In vitro
1. antibodies against E-cadherin can block adhesion of normal epithelial cells to each other, leading to invasion of collegen gels

In vivo
1. staining for E-cadherin
2. Strong in central tumour
3. Disappears in cells at invasive edge

Question 10

What is the evidence for intergrin roles in cancer?

Answer 10

Blockade of integrin adhesino with RGD-containing peptides can block metastasis

Experimental metastasis assay:
1. injected B16-F10 melanoma cells + GRGDS peptide which competes for adhesion to integrin
2. reduced lung tumour metastasis with increasing dose of peptide