Chapter 2 - Anti-angiogenic Therapeutics Flashcards Preview

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Flashcards in Chapter 2 - Anti-angiogenic Therapeutics Deck (81):
1

Where is angiogenesis NORMALLY seen

During development and organ growth

In adults:
Reproduction and wound healing
Endothelial turnover is low

2

What is disease-associated angiogenesis called?

Neovascularisation

3

What was symbolic for angiogenesis discovery in 1983?

Singer et al partially purified a protein that induced vascular leakage, vascular permeability factor (VPF)

4

What year and by whom was VPF purified?

1983
Singer et al

5

What year was VEGF purified?

1989

6

What was symbolic for angiogenesis discovery in 1989?

Vascular endothelial growth factor (VEGF) was purified and cloned

7

What is VEGF?

A secreted polypeptide, which binds to cell surface receptors

8

How does VEGF interact with endothelial cells?

Mitogen (causes cell division), chemoattractant (causes cell movement), survival factor

9

Explain the effects of a VEGF knockout in embryogenesis

Loss of one copy of the VEGF gene causes aberrant blood vessel and death in embryogenesis

Can be shown in VEGF +/- knockout mice

10

How does VEGF receptor gene disruption affect embryos

Lethal

Can been seen by VEGF morpholino injections into zebra fish showing a reduction in vasculature.

11

What synonyms for VEGF-R1 and VEGF-R2

1:
Flt-1

2:
Flk-1

12

Where can neovascularisation be seen?

Tumors

13

VEGF-A signalling via VEGFR2 for migration survival

VEGF-A ---> VEGFR2 ---> Y1214 ---> Rac ---> migration survival

14

VEGF-A signalling via VEGFR2 for survival

VEGF-A ---> VEGFR2 ---> PI3K ---> Akt ---> Bad ---> Survival

15

VEGF-A signalling via VEGFR2 for gene expression and DNA synthesis

VEGF-A ---> VEGFR2 ---> 1175Y ---> PLC- gamma ---> KCC ---> Raf-1 ---> MEK1/2 ---> ERK1/2 ---> gene expression and DNA synthesis

16

Describe the function of semaphorins in angiogenesis

Act at NRP1 and NRP2 in sensory neurones

Aids sensory axon all guidance
Causes growth cone collapse

17

Describe the function of VEGFs in angiogenesis at endothelial cells

Act at:
NRP1 vascular maturation, branching, cardiac development
NRP2 lymphangiogenesis
VEGFR3, VEGFR4

18

Mechanisms of blood vessel formation

1. Sprouting angiogenesis
2. Vasculogenesis
3. Intussusception
4. Vessel co-option
5. Vascular mimicry
6. Tumour cell --> EC differentiation

19

What is angiogenesis?

A highly regulated process by which blood vessels are formed

20

List the steps of angiogenic sprouting.

1. VEGF activation of tip cells via VEGFR2
- Suppression of tip cell phenotype in neighbouring cells via D114/notch
2. Tip cell guidance along VEGF gradient
3. Stalk elongation
4. Lumen formation
5. Pericyte recruitment by endothelial derived PDGF-BB

21

5 types of pathophysiological angiogenesis in adults

1. cancer
2. ocular neovascularising disease e.g. wet AMD
3. Psoriasis
4. Cardiovascular disease
5. Diabetes

22

Give the stepwise mechanism to the formation of a metastasised tumour from a somatic cell

somatic mutation --> small avascular tumour --> tumour secretion of angiogenic factors --> rapid tumour growth and metastasis

23

where do new vessels form in neovascularisation?

from pre-existing vascularisation

24

why is tumour angiogenesis important for cancerous tissue

required for tumour growth and metastasis

25

give a stepwise mechanism for the production of tumourogenic vessels

1. tumour secretes angiogenic factors
2. proteolytic destruction of extracellular maxtric (ECM)
3. endothelial proliferation and migration
4. appearance of new tumour vascularisation
5. intravasation

26

give three pro-angiogenic factors

VEGF
FGF
PDGF

27

Give three anti-angiogenic factors

angiostatin
endostatin
thrombospondin

28

what are the rates of endothelial cell proliferation in normal and tumour vessels?

3-13 / day
47-2000 / day

29

describe the physical features of tumour vessels

distorted and disorganised architecture
sluggish bloodflow
shunts
deadends

30

what is intravasation

leakiness of tumour vessels

31

what characteristic of tumour vessels does intravasation lead to?

high interstitial pressure and regions of hypoxia

32

what problems does cancer cause for conventional therapies

tumour vessel abnormalities reduce the delivery and response of the therapy

33

how does the physical structure of normal blood vessels allow them to function properly

hierarchially organised, with vessels that are sufficiently close to ensure adequate nutrient and oxygen supply to all cells.

34

how does the physical structure of tumour blood vessels prevent them from proper functionality

chaotic, dilated, turtous, far apart, with a sluggish bloodflow

35

Importance of tumour hypoxia

1. solid tumours contain regions of v. low [O2] (hypoxia)
2. hypoxia induces a metabolic switch from oxidative to glycolytic metabolism
3. hypoxia induces the production of VEGF and other angiogenic cytokines
4. hypoxic tumour cells are more resistant to radio- and chemotherapy
5. hypoxia selects for a more malignant phenotype, increases mutation rates and increases expression of genes associated with angiogenesis and invasion
6. hypoxia is associated with a more metastatic phenotype, making it a more prognostic determinant of cancer progression and therapeutic response.

36

how can solid tumours be targeted?

hypoxia-selected therapies are being developed targeting hypoxia-inducible factor 1 (HIF1) transcription factor.

37

what role does HIF1 have in cancer?

1. Master regulator of the hypoxic response
2. under hypoxia, it escapes degradation, enabling hetero-dimerisation with HIF-1b and subsequent binding to hypoxic response elements within the promotor region of target genes e.g. VEGF, PDGF
3. Positive regulation of tumour survival, progression, metastasis
4. clinical studies demonstrates that HIF1 is associated with increased patient mortality

38

what tumour vessel abnormalities are targetable?

1. rapidly dividing
2. accessibility
3. 1 capillary supports many tumour cells
4. no drug-resistance, more genetically normal
5. applicable to many solid tumours

39

what three advanced treatments can be used against tumour vessels?

1. vascular disrupting agents
2. small molecule inhibitors
3. antibodies

40

how does combretastatin work?

tubulin binding agent/ colchicine binding site
targets established tumour vessels
selectively inhibits tumour bloodflow
destroys all but tumor rim, which continues to grow

41

give an example of a combretastatin prodrug

zybrestat: CA-4-P, combretastatin prodrug

42

give an example of a colchicine prodrug

ZD6126: colchicine analogue prodrug

43

what therapy can act intracellular?

small molecules... antibodies can only act extracellular and on secreted bodies.

44

what therapy is orally available?

small molecules... antibodies are intravenous

45

what therapy can cross BBB

small molecules, when designed to.. Antibodies cannot

46

what are the sizes of small molecules and antiobodies

~800 Da for small molecules
~50-150 kDa for antibodies

47

which is more stable, antibody or small molecule

antibody

48

which is more specific, small molecule or antibody

antibody

49

do antibodies cause immonogenecity?

yes, small molecules do not.

50

how can solid tumours be targeted?

hypoxia-selected therapies are being developed targeting hypoxia-inducible factor 1 (HIF1) transcription factor.

51

what role does HIF1 have in cancer?

1. Master regulator of the hypoxic response
2. under hypoxia, it escapes degradation, enabling hetero-dimerisation with HIF-1b and subsequent binding to hypoxic response elements within the promotor region of target genes e.g. VEGF, PDGF
3. Positive regulation of tumour survival, progression, metastasis
4. clinical studies demonstrates that HIF1 is associated with increased patient mortality

52

what tumour vessel abnormalities are targetable?

1. rapidly dividing
2. accessibility
3. 1 capillary supports many tumour cells
4. no drug-resistance, more genetically normal
5. applicable to many solid tumours

53

what three advanced treatments can be used against tumour vessels?

1. vascular disrupting agents
2. small molecule inhibitors
3. antibodies

54

how does combretastatin work?

tubulin binding agent/ colchicine binding site
targets established tumour vessels
selectively inhibits tumour bloodflow
destroys all but tumor rim, which continues to grow

55

give an example of a combretastatin prodrug

zybrestat: CA-4-P, combretastatin prodrug

56

mechanisms of resistance to antiangiogenic therapy

1. role of multiple angiogenic factors at different stages of tumour progression
2. different factors required for capillary formation, stabilisation, pericyte recruitment.
3. mature, pericyte covered vessels more resistant to anti-VEGF drugs, and to pruning
4. endothelial multidrug resistance
5. EPCs recuited independently of VEGF
6. angiogenesis inhibitors do not prevent metastatic spread via lymphatics

57

what therapy can act intracellular?

small molecules... antibodies can only act extracellular and on secreted bodies.

58

what therapy is orally available?

small molecules... antibodies are intravenous

59

what therapy can cross BBB

small molecules, when designed to.. Antibodies cannot

60

what are the sizes of small molecules and antiobodies

~800 Da for small molecules
~50-150 kDa for antibodies

61

which is more stable, antibody or small molecule

antibody

62

which is more specific, small molecule or antibody

antibody

63

do antibodies cause immonogenecity?

yes, small molecules do not.

64

give an example of a small molecule tyrosine kinase inhibitor

Gleevec (imatinib mesylate)

used for CML and gastrointestinal stromal tumours

blocks cell division and growth by preventing activation of growth factor receptor PDGFR

65

give an inhibitor of vascular endothelial growth factor receptor (VEGFR)

ZD6474 for NSCLC

blocks angiogenesis

66

give an anti-angiogenesis antibody

avastin

-blocks growth factor function and signalling
- recently withdrawn for us in breast cancer due to sever cardiovascular toxicity

67

problems associated with avastin?

1. expensive
2. adverse side effects: hypertension, stroke, myocardial infarction, haemorrhage
3. drug resistance
4. dose selection: too high a dose my prune vasculature too much, thus reducing efficacy of chemotherapeutic drugs

68

what is the impact of altering VEGF levels and activity on the adult human vasculature?

1. increases blood flow and reduces blood pressure in animal models of peripheral and cardiac ischaemic disease
2. stimulates endothelial production of NO and prostacyclin
required for maintenance of microvasculature in tissues and organs e.g. kidney
3. VEGF gene and protein treatments in clinical trials for ischaemic heart disease are safe, but hypotension is an effect of VEGF protein administration

69

what evidence is there for resistance to anti-angiogenic therapy?

1. in cancer trials bevacizumab/avastin increases period of progrression-free survival but has generally had little impact on overall survival
2. antiangiogenic treatments in mouse models of cancer have been shown to increase metastatic tumour growth (Ebos et al 2009)

70

mechanisms of resistance to antiangiogenic therapy

1. role of multiple angiogenic factors at different stages of tumour progression
2. different factors required for capillary formation, stabilisation, pericyte recruitment.
3. mature, pericyte covered vessels more resistant to anti-VEGF drugs, and to pruning
4. endothelial multidrug resistance
5. EPCs recuited independently of VEGF
6. angiogenesis inhibitors do not prevent metastatic spread via lymphatics

71

give 2 anti-VEGF therapies for eye disease

lucentis (Fab fragment of Bevacizumab)
Macugen

both approved for wet age-related macular degeneration (wet AMD)

72

what is the main use of anti-VEGF therapies for eye disease

reduce oedema

73

what is diabetes

group of metabolic disorders that share the common feature of hyperglycemia

74

what types of diabetes are there?

type 1:
absolute deficiency of insulin caused by beta cell destruction

type 2:
combination of peripheral resistance to insulin action and inadequate secretory response

75

what does diabetes often lead to

end stage renal disease
adult onset blindness
non-traumatic lower extremity amputation

76

describe pre-proliferative diabetic retinopathy

increased vascular permeability
venous dilation
micro-aneurysms
intraretinal hemorrhage
fluid leakage
retinal ischaemia

77

describe proliferative diabetic retinopathy

neovascularisation
vitreous haemorrhage
fibrous proliferation

78

what is the treatment for diabetic retinopathy

primary prevention:
strict glycemic control
blood pressure control

secondary prevention:
annual eye exams

tertiary prevention:
laser therapy to seal leaking blood vessels
vitrectomy

79

what is a more recent treatment for diabetic retinopathy

anti-VEGF antibody treatment for amcular oedema and proliferative retinopathy

80

what is up-regulated in the initial phase of diabetic nephropathy?

VEGF-A

81

What may explain the decline of VEGF-A in the later phase of diabetic nephropathy?

disruption to podocyted and tubular cells in chronic kidney damage