Tumour angiogenesis

Question 1

What is angiogenesis? What is it for normally?

Answer 1

New endothelial cells from pre-existing ones that will form new vessels. Development and growth, wound healing, reproductive system and muscle growth after exercise.

Question 2

What are capillaries made of and what is their functions?

Answer 2

Pericytes, basement membrane, and single endothelial layer

Question 3

What is the consequences of angiogenesis in disease?

Answer 3

Excessive: Tumour metastasis and growth
Arthiritis
Vascular malformation
Insufficient:
Coronary artery disease
myocardial infraction

Question 4

What activates angiogenic switch?

Answer 4

Hypoxia, nutrient depletion and oncogenes. Through growth factors mostly and cytokines that bind to receptors on cell surface and mediate processes such as prolferation, migration, differnetiation

Question 5

List some pro and anti angiogenic factors

Answer 5

Pro: FGF, HGH, VEGF, ang2, ang1, EGF, IL8, MMP
Anti: Thrombostin, endostatin, platelet factor 4, fibronectin

Question 6

List the steps in sprouting angiognesis

Answer 6

1. Production and release of angiogenic factors
2. Activation by binding to endothelial cells:
   There will be degradation of ECM and remodelling
   Loosening of cell cell adhesion
   Tip cell selection Proliferation and migration of tip cells
   Proliferation of stalk cells
   Form a vascular lumen and capillaries
   Stabilize junction
   Recruit pericyte and vessel maturation

Question 7

What is the functions of VEGF?

Answer 7

1. Permeabilize the vessels
2. Migrate, proliferate, survival of endothelila cells
3. Trigger matrix degrading protease
4. Promoter of endothelial cells to a 3D vessel

Question 8

What are the members of VEGF family? and which ones are involved in cancer?

Answer 8

VEGFA, VEGFB, C, D, placental growth factor. A,B associated with cancer

Question 9

What is the difference/similarities in gene structure between these VEGF’S?

Answer 9

VEGF A has 8 exons and the rest have 7, VEGF A has heparin domain that is positively charged. They all have different proteins with different functions, they are all on different chromosomes. But have homologous VEGF domain

Question 10

How is VEGF family so diverse with so many isoforms?

Answer 10

They undergo alternative splicing, proteolysis to produce active forms

Question 11

Explain how hypoxia regulates VEGF expression

Answer 11

Normoxia HIF is destabilized via hydroxylation and ubiquitylated and degraded. But in hypoxia there will be stabilizationn because VHL will be degraded and it’ll translocate to the nucleus and dimerize with HIFB and transcribe VEGF genes and angiogenesis will ensue

Question 12

VEGF expression by tumour cells will bind to receptors on endothelial cells what are those receptors?

Answer 12

Heparan sulfate proteoglycan
soluble VEGFR
Tyrosine kinase receptors
Neuropilin co-receptor

Question 13

VEGF TKR how does it work when it binds to VEGF?

Answer 13

Receptor dimerize, receptor activated and phosphorylated in the intracellular domain and then activates downstream targets

Question 14

How does soluble VEGFR work?

Answer 14

It is the ectodomain of VEGFR, it traps the VEGF and prevents it from activating the intracellular domain in transmembrane receptors

Question 15

How does neuropilin co-receptor work?

Answer 15

It binds to VEGF A forms a VEGF ddependent complex and this will change the pathways that are activates, it enhances the signalling by activating different pathways depending if the complex is formed or not

Question 16

How does heparan sulphate proglycan co-receptor work?

Answer 16

They have no catalytic function binds to long isoforms of VEGF

Question 17

How do we account for the many different effects of VEGF signalling cascade

Answer 17

Proteins bind to the SH2 domain and depending on what TYR gets hosphorylated different processes will be modulated.
TYR1175 survival and proliferation
TYR 951 metastasis and vascular permeability

Question 18

What’s degradation of ECM by? What cell do they come from? What is it controlled by?

Answer 18

It’s by zinc dependent enzymes,endothelial cells or tumour or stromal.
TIMP

Question 19

What is the main protein involved in the loosening of cell to cell junctions? And what is the effect

Answer 19

VE cadherin, it increases permeability by VEGFR dissociating from VE cadherin when VEGF binds

Question 20

How do cells sprout and what determines if the cells are tip or stalk?

Answer 20

They grow toward the chemotatic gradient of VEGF, the cells that have notch activation are stalk cells while the notch inactivation are the tip cells

Question 21

How is lumen formed?

Answer 21

The vacuoles will join

Question 22

What is anastomosis?

Answer 22

Joining of many capillaries

Question 23

Outline the steps in vessel maturation

Answer 23

VEGF recruits myeloid cells that support maturation
The endothelial cells will stabilize their junction
Tip cells produce PDGF-BB that will recruit the pericyte
Pericyte will adhere to endothelial cells and further proliferation can’t occur
The vessels are mature

Question 24

Non sprouting angiogenesis, what are two ways?

Answer 24

Vasculogenesis-endothelial progenitor cells recruited to tumour and they differentiate to mature tumour endothelial cells
Or cancer stem cells can differentiate into them
Vasculogenesis mimicry- The tumour cells will differentiate into them

Question 25

What other ways can tumours vascularize?

Answer 25

Through vessel co-option where the tumours grow alongside of capillares.
Or intussusceptive microvascular growth- where the vessel lumens part and the vessels enlarge

Question 26

What are the functional and structural abnormalities found in tumour vascularization?

Answer 26

Erratic blood flow, low oxygen level, increased IF pressure, more leakage, disorganized, less pericyte coverage, enlarged diameter, destabilization junctions, disorganized

Question 27

What are the anti-cancer strategies when targetting angiogenesis and what is their mechanism and consequences?

Answer 27

Vascular disruption-Shuts down selectively established tumor vessels
Intermitent dosage
hemorrhage necrosis
Induces necrosis of tumour cells
Anti-angiogenesis- Stops new vessels from forming
Continuos dosage

Question 28

Give examples of drugs used when targetting angiogenesis

Answer 28

Bevasizumab- antibody against VEGF A neutralizing
VEGF trap- soluble VEGF
Iressa- blocks EGFR and productionof VEGF, BFGF
Sunitinib-small molecules of VEGFR signalling inhibitors

Question 29

Examples of angiogenesis inhibitor stimulation

Answer 29

Tamoxifen- induces endostatin

Question 30

How is renal cell cancer treated?

Answer 30

VHL is often degraded in this type of cancer leading to enhanced activation of VEGF, using anti-angiogenic strategy has good progression free disease and overall survival

Question 31

What are the problems with using anti-angiogenic treatment?

Answer 31

Tumour response is temporary usually because of the microenvironment reccurence is very common in many different ways such as pro-angiogenic inflammatory response, recruiting pericyte, increased invasiveness.
Toxicity- such as hypertension
Treatment resistance

Question 32

What are possible ways to mitigate these problems? And how does this optimize treatment

Answer 32

Using combination therapy, when using chem- or radiotherapy along with administering the anti angiogenic drug not only the endothelial cells will be targetted but also cancer cells. Also when using this AA drug it will normalize the vessels which will make them less resistance to other types of therapy.

Question 33

What is “window of opportunity”?

Answer 33

It is referring to the timing of the dosage of anti-angiogenic drug, it can’t be for too long or there will be excessive pruning and enhanced angiogenesis and this will make it more resistant to chemo or radio-therapy and it can’t be too little or it won’t be effective in sensitizing the tumour, so it’s referring to optimal dosage that improves delivery.

Question 34

What’s the difference between predictive and prognostic biomarkers?

Answer 34

Predictive is looking at the response of the patient after treatment that correlates wtih clinical response.
Prognostic is seeing the overall outcome of the diease based on that biomarker

Question 35

Are there any angiogenesis biomarkers and what are potential ones?

Answer 35

No, but VEGF isomers are potential ones.

Question 36

What are some examples of vascular distruption drugs?

Answer 36

Tubulin binding agents(CA4P) and integrin antagonist

Question 37

What are the problems with CPA4 or VDA? And what are ways to optimize treatment?

Answer 37

The tumour rim is resistant. VDA induces hypoxia, vessel loss and collapse, permeability macrophage recruitment. Combination treatments are optimal because target different cell populations and makes vessels more sensitive to VDA after other treatment, even using inhibitors with macrophage recruitment makes it more effective.