Angiogenesis

Question 1

Tumour cells growth until conditions are hypoxic and then secrete factors that accelerate (a)?

Answer 1

Angiogenesis

Question 2

What secrets Erythropoietin?

Answer 2

Kidneys (and rare cancer types)

Question 3

What is the affect of erythropoietin?

Answer 3

Increased blood count

Question 4

What is the TF for erythropoietin?

Answer 4

HIF

Question 5

What subunits make up HIF?

Answer 5

Heterodimer - HIF1A or HIF2A or HIF3A and HIF1B

Question 6

What is the HIF binding site?

Answer 6

CGTG - hormone response site (HRE)

Question 7

What is lactacystin?

Answer 7

A protease inhibitor, to show that HIF is degraded normoxia is no longer degraded

Question 8

What is E3?

Answer 8

Ubiquitin ligase

Question 9

What E2?

Answer 9

Ubiquitin conjugating enzyme

Question 10

What E1?

Answer 10

Ubiquitin activating enzyme

Question 11

What is Von Hippel Lindau Syndrome?

Answer 11

Mutated form of VHL so can not degrade so is cancer prone. Tumours are well vascularised

Question 12

What is the primary structure of the VHL transcript?

Answer 12

Two functional domains alpha and beta. Mutation is always in beta domain - the part that binds HIF.
When alpha domain is removed VHL can still bind HIF it is just unable to regulate its levels.

Question 13

What does the CTD of VHL have homology to?

Answer 13

Skp2 - a part of a ubiquitin ligase

Question 14

Which protein does the alpha domain of VHL recruit?

Answer 14

3 ubiquitin ligase protein - Cullin2, Elo C and Elo B - tag HIFA for the degradation by the proteasome

Question 15

Is VHL inhibited in hypoxic cells?

Answer 15

Yes

Question 16

What is prolyl-4-hydroylase?

Answer 16

Oxygen sensing enzyme that modifies proline residues by adding hydroxyl groups (dependent on a-kg, intermediate of TCA)

Question 17

What is the affect of prolyl-4-hydrolase on HIFA?

Answer 17

Hydroxylates p405 and p564 and inactivates it

Question 18

What is HIF a TF for?

Answer 18

Erythropoietin, VEGF, glycolytic enzymes - (relevant as hypoxic cells rely more on glycolysis than aerobic respiration

Question 19

What is the weight of vascular epithelial growth factor?

Answer 19

22.5kDa

Question 20

What is VEGF?

Answer 20

Secreted factor which causes increased vascularisation and permeability

Question 21

What are the specific roles of:

a) VEGF1
b) VEG2
c) VEG3

Answer 21

a) increased permeability
b) increased vascularisation
c) increased lympangiogenesis

Question 22

What is the intracellular domain of VEGFR?

Answer 22

Tyrosine kinase - trans-autophosphorylation as in EGFR

Question 23

Where are VEGFR’s found?

Answer 23

Epithelial cells of blood vessels - activates MAP kinase PI3K pathway resulting in proliferation ad formation of new capillaries

Question 24

Under what conditions does HIF bind p53?

Answer 24

Very high levels of HIF

Question 25

Why are high levels of HIF required for binding of p53?

Answer 25

HIF has low affinity for p53

Question 26

At what site of p53 does HIF bind?

Answer 26

N terminal - MDM2 binding site

Question 27

What is the affect of HIF binding p53?

Answer 27

Stabilisation of p53 and initiation of arrest and apoptotic genes and reduction in HIF signalling

Question 28

What is avastin?

Answer 28

Anti-VEGF monoclonal antibody - prevents extracellular functions of HIF

Question 29

Why is avastin not a miraculous treatment?

Answer 29

Only extends life by 2-5 months when used with other chemotherapies - doesn’t cause regression of vascularisation. Also made vessels leakier.
Also puts selective pressure on cells because of hypoxia

Question 30

What is endostatin?

Answer 30

Similar function to Avastin (small so has to be conjugated to Fc domain to increase lifespan)

Question 31

What is biphasic endostatin?

Answer 31

Too little and no affect

Too much increase in tumour growth

Question 32

What is the mechanism endostatin?

Answer 32

It is not known