Tumour Angiogenesis ,Invasion and Metastasis

Question 1

1.What are the three main characteristics of malignant tumours?

Answer 1

Growth: ( unlimited growth as long as adequate blood supply)

Invasivness: Migration of- tumour cells —> surrounding stroma–> Distant Organs ( via vascular or lymphatic channels)

Metastasis: Spread of tumour from primary tumour ->Secondary tumours

Question 2

2.What is the sequential process of metastasis?

7 steps

Answer 2

1. One clonal cell -> GROWTH
2. New BLOOD VESSELS surround tumour ( o2 and nutrients)
3. Cells LOOSE CHARACTERISTICS. (less epithelial and change to become more motile)
4. INVADE the blood vessels surrounding tumours
5. AGGREGATION of circulating cells will lodge at distant sites
6. MOVE OUT of capillary
7. Aggregate of cells –> Proliferate –> Metastasise –> Cycle Repeats

Question 3

3. Fill in the blank:

“Process of cancer metastasis consists of sequential, *** and selective steps with some *** elements.

Answer 3

Interlinked

Stochastic

Question 4

4. What is the outcome of each stage of metastasis influenced by?

Answer 4

interaction of metastatic cellular subpopulations with homeostatic factors

Question 5

5. Each step of metastatic cascade is potentially rate limiting, what does this mean?

Answer 5

That if a step is not completed effectively, it will have consequences on further steps

Question 6

6. What are the 5 key steps in cancer progression?

Answer 6

1. Extensive mutagenic and epigenetic changes followed by clonal selection
2. To overcome hypoxia –> Angiogenesis
3. EMT ( epithelial –> mesenchymal transition)= intravasation and extravasation
4. Micrometastases –> Expand –> Colonisation of target organs
5. Release of metastatic cells that have ability to colonise

Question 7

7. What is the difference between Angiogenesis and Vasculogensis?

Answer 7

Angiogenesis = The formation of new blood vessels from pre-existing vessels whereas vasculogenesis is the formation of new blood vessels from new progenitors

Question 8

8.What are the the three types of Angiogenesis?Give examples of each

Answer 8

1. Developmental/Vasculogenesis (Organ Growth)
2. Normal Angiogenesis (Wound repair,Placenta during pregnancy , cycling ovary)
3. Pathological Angiogenesis (Tumour angiogenesis, Ocular and inflammatory disorders)

Question 9

9. How does tumour angiogenesis occur?

Answer 9

• > Tumour divides loads before it gets to a capillary
• > Outgrows existing nutrients
• > Tumour becomes hypoxic
• > This is a stimulus for tumour to secrete angiogenic factors (act on nearby capillaries)
• Nearby capillaries starts to have tip formation in the vessel - they’re own proliferation is upgregulated so new blood vessels form around the tumour
• > Cells shed off - escape through local blood supply - develop into micro-metastases

Question 10

10. What the max size a tumour will grow to without their own blood size due to hypoxia?

Answer 10

2mm

Question 11

11. What is Angiogenesis promoted by?

Answer 11

Hypoxia

Question 12

12.What is Hypoxia?

Answer 12

Low oxygen tension

<1% O2

Question 13

13. Fill in the blank:

“ Hypoxia increases with increasing distance **’

Answer 13

Capillaries

Question 14

14. What does hypoxia activate?

Answer 14

Transcription of genes involved in:

• angiogenesis
• tumour cell migration
• metastasis

Question 15

15.Some tumour cell produce angiogenic factors (stimulate directional growth of endothelial cells)
List 4:

Answer 15

-Vascular Endothelial Growth Factor (VEGF)

Fibroblast Growth Factor-2 (FGF-2)

Transforming Growth Factor-β (TGF- β)

Hepatocyte growth factor/scatter factor (HGF/SF)

Question 16

16. The following questions refer to angiogenic factors:
    - What are they secreted by?
    - How are they stored?
    - How are they released from storage?

Answer 16

• Secreted by tumour cells
• Stored bound to components of the extracellular matrix
• May be released by enzymes called matrix metalloproteinases

Question 17

17. Briefly explain the process of Vascular Endothelial growth factor (VEGF) signalling?

Answer 17

Cancer becomes hypoxic –> VEGF (GF for blood vessels) secretion out of tumour –> VEGF binds to VEGF receptor in endothelial cells–>Switches on downstream signalling–>Pathways are upgregulated in tumour cels –>Growth of endothelial cells–>Activate PKB/AKT pathway–> Gene transcription switched on–>Vessels become leaky/permeable = allows cells to move between tumour and endothelial cell.

Question 18

18.What are three consequences of tumour cell Motility and Invasion?

Answer 18

1. Increased mechanical pressure ( because of cell prolif)
2. Increased Motility (EMT)
3. Increased production of degradative enzymes (by tumour and stromal cells)

Question 19

19. During the EMT , we have gene down regulation. What does this cause the LOSS of?

Answer 19

• Epithelial Shape
• Cell Polarity
• Cytokeratin intermediate filament expression
• Epithelial Adherence junction protein E-Cadherin

Question 20

20. During EMT, we have gene up regulation. What do we GAIN from this?

Answer 20

• Fibroblast shape and motility
• Invasivness
• Vimentin intermediate filament expression
• Mesenchymal gene expression
• Protease Secretion(MMP-2, MMP-9)

Question 21

21. Give three examples of mesenchymal genes that would be expressed during EMT

Answer 21

• Fibronectin
• PDGF receptor
• avbeta6 integrin

Question 22

22. The following questions are about E-Cadherins:
    - What type of adhesion molecules are they?
    - What do they bind to in cells?
    - What are they dependant on?
    - Do they inhibitor or promote invasivness?

Answer 22

• Homotypic Adhesion molecules (adhesion to cells with same cadherin)
• Bind to beta-catenin in cells
• Calcium dependant?
• Inhibit invasivness

Question 23

23. How do E-Cadherins inhibit invasiveness?

Answer 23

Okay so in a normal cell , there are tight junctions due to the adhesion molecules, when they proliferate they remain as a monolayer of normal cells (with tight junctions between) and so contact inhibition-they arent touching``````

Question 24

24. When there is a loss of E-Cadherin or a mutation in E-cadherin what would happen to cell-cell adhesion?

Answer 24

So when there is a loss of E-cadherin, there is disrupted cell-cell adhesion, rather than having a monolayer of normal cells,the cells grow on top of each other and so there is contact
Therefore contact inhibition is LOST

Question 25

25. What are integrins? - heterotypic or homotypic? - what do they bind to? Via what 3 things? - What does this allow for?

Answer 25

They are cell-matrix heterotypic adhesion molecules , they bind to the extracellular matrix (via collagen, fibronectin and laminin) to allow cell migration

Question 26

26.Are integrins heterodimers or homodimers?Give their subunits

Answer 26

Heterodimers with alpha and beta sub units

Question 27

27. In what way does the stromal cell contribute to tumour progression?

Answer 27

The stromal cell releases factors ( eg macrophages, fibroblasts and mast cells) these factors induce : - Angiogenic factors - Growth Factors - Cytokines - Proteases

Question 28

28. Give a specific example of how the stromal cell can contribute to tumour progression?

Answer 28

The stromal cell releases uPA (Urokinase-type plasminogen activator), this is activated by tumour cells -This increases plasmin production and cell movement -The plasmin production-->Activated matrix metalloproteinases (MMPs) > MMPs allow invasion by degrading extracellular matrix (ECM) --> releases matrix-bound angiogenic factors

Question 29

19. List the appropriate site of tumour metastasis for the following cancers: - Breast Cancer - Colorectal Cancer - Pancreatic Cancer

Answer 29

Breast Cancer= Brain, lungs, liver Colorectal Cancer= Lungs Prostatic Cancer = Arm(bone) Pancreatic Cancer = Lungs

Question 30

30. List the steps involved in Cancer Metastasis?

Answer 30

1. Primary tumour formation 2. Localised Invasion 3. intravasation ( tumour cell INTO blood vessel) 4. Transport through circulation 5. Arrest in microvessels of various organs 6. Extravasation (Tumour OUT of blood vessel , into target tissue) 7. Formation Micrometastasis 8. Formation of Macrometastasis

Question 31

31. In the process of cancer dissemination, which steps are successful, which are inefficient. USE figures

Answer 31

Tumour cells can extravasate successfully (>80%) but the last two steps are very inefficient (<0.02% of cells actually form micrometastases).

Question 32

32. What are the names of two hypothesis to determine the pattern of tumour spread?

Answer 32

1. Mechanical Hypothesis | 2. Seed and soil Hypothesis

Question 33

33. What is the mechanical hypothesis to what determines the patterns of how tumours spread?

Answer 33

Basically it depends on anatomical considerations so whats near the tumour eg blood and lymphatic vessels, it will then get entrapped by capillary beds

Question 34

34. What is the size of a carcinoma cell in comparison to a capillary?

Answer 34

Carcinoma Cell = 20-30um Capillary = 8um

Question 35

What is the seed and soil hypothesis for what determines the pattern of tumours spread?

Answer 35

* Specific adhesions between tumour cells and endothelial cells in the target organ create a favourable environment in the target organ for colonisation. * Genetic alterations acquired during progression allow tumour cells to metastasize.

Question 36

36. In 1971 Judah Folkman came up with the angiogenesis hypothesis. What is this?

Answer 36

Tumour growth dependent on new blood vessel growth | “If a tumor could be held indefinitely in the vascularised dormant state….it is possible that metastases will not arise”

Question 37

37. There has been a paradigm shift (big change) in cancer therapy. How?

Answer 37

Now both the tumour and microvascular compartment are valid therapeutic targets

Question 38

38. What cancer is highly angiogenic

Answer 38

Kidney cancer/renal cell carcinoma

Question 39

39. How can highly angiogenic tumours be targeted?

Answer 39

Highly angiogenic tumours can be targeted by blocking blood vessels of the tumour causing regression to an extent.

Question 40

40. What is Avastin? | What cancers can it treat?

Answer 40

First specific anti-angiogenesis drug in 2013 was the second biggest selling oncology product Approved for colorectal, lung, kidney and ovarian cancers and eye diseases

Question 41

41. What is the mechanism of action of Avastin/Bevacizumb?

Answer 41

oAvastin is a monoclonal antibody that binds to VEGF to prevent VEGF binding to receptors on endothelial cells oThis prevents intracellular phosphorylation of receptor so no dimerisation and therefore no downstream signalling.