Angiogenesis 1 Flashcards
What specific molecule does Idelalisib target?
1 mark
PI3Kδ
Why is idelalib suitable for patient with follicular lymphoma?
2 marks
- p110 delta isoform particularly expressed in lymphocytes and in the cancer has frequent mutations so want to target this isoform.
- Delta used for specialised signalling in specialised cells
Would NVP-BKM120 theoretically work on this patient?
(from Q2)
2 marks
Yes – a pan class 1a pi3k inhibitor and hits all the isoforms alpha, beta and delta. So it would theoretically
Why not give the patient (Q3) NVP-BKM120?
1 mark
Too broad at targeting and would have too many off-target effects. Specifically affects glucose metabolism as impact AKT signalling
Outline the different structures in the basic histology of a blood vessel.
3 marks
- Endothelial cell:
- Basic bv cell (forms endothelium)
- Basement membrane:
- surrounds endothelium
- Pericytes:
- Perivascular cells i.e. related to vascular smooth muscle
- Share basement membrane with endothelium
- Abundant and tightly attached
- Structural support
What is necrosis?
1 mark
Cell death by accident or trauma. Beyond ~100-200um of a blood vessel cells hypoxic and die of necrosis
Red Image: around capillaries oxygenated area and bright read areas are hypoxic
Blue image: granular staining indicates cells dying of necrosis
What causes necrosis?
1 mark
Hypoxia
What is angiogenesis?
1 mark
Formation of new blood vessels by ‘sprouting’ from new ones
Give some charactersitics of tumour blood vessels.
5 marks
- Irregularly shapes
- Pericytes loosely attached
- Fail to stabilise properly
- Dilated
- Lack organisation and leaky
What happens in the avascular phase of a tumour?
1 mark
Dormant lesion and no angiogenesis
What happens in the vascular phase of a tumour?
1 mark
Activation of angiogenesis, allowing for tumour growth and spread
Give a basic overview of the processes involved in angiogenesis.
5 marks
- Response to angiogenic stimulus, pericytes come off blood vessel destablizing it
- BV dilates new vessels sprout and grow towards angiogenic stimulus
- Mature will recruit pericytes back - not enough so not v tightly attatched
- Vasculature v dynamic & instable
- Process continues as areas become hypoxic
List a few examples of activators and inhibitors of angiogenesis.
6 marks
- ACTIVATORS:
- Matrix metalloproteinases (MMPs) - breakdown ECM so cells can pass basement membrane surrounding endothelium and have to sprout and grow
- Nitric oxide - involved in vasodilation
- VEGF - antiVEGF therapy with a humanized monoclonal antibody is an approved method to treat colon cancer and some types of nonsmall-cell lung cancers and metastatic breast cancer. best in combination with traditional chemotherapy or radiotherapy. ( Pelengaris et al 2013)
- INHIBITORS:
- Angiostatin
- Endostatin
- Thrombospondin 1 &2
What is HIF?
4 marks
- Hypoxia-inducible factor
- Made of one HIF-1a and one HIF-1b subunit
- Both^^ mRNA constittutively expressed
- Regulated at HIF-1alpha protein level
What does HIF do?
2 marks
- Drives transctiption of pro-oncogene genes target is VEGF as increases distribution of oxygen
- HIF1alpha levels regulated by oxygen levles - normoxic = 20% O2 so HIF1a levels down and by VHL tumour suppresor protein
What happens in a normoxic environment?
2 marks
- O2 levels activate prolyl 4 hydorxylase this modiefies specific prolines on HIF1 alpha
- VHL protein binds to hydroxylated proline promoting ubiquitynylation and degradation of HIF1a protein
What happens to HIF1alpha in a hypoxic environment?
1 mark
- Prolyl hydroxylase is not activated and HIF1alpha is present to form complete transcription factor
What does VHL do to HIF1 alpha in a normoxic environment?
1 mark
- VHL recruits range of proteins to site so alpha subunit is polyubiquitinated and then targeted for degradation by proteosomal pathway
- No alpha subunit present no degradation
What is a therapeutic way to target HID1alpha?
1 mark
Enhance HIF1alpha protein degradation and so prevent HIF binding to gene promoter and inhibiting HIF1alpha production
How does the expression of the HIF-1a isoforms change over time?
3 marks
- 3 isforms - HIF - 1,2,3alpha
- HIF1a involved in acute response to hypoxia and increases and falls after 12 hrs
- Hypoxia sustained get expression of 2 and 3 - switch between isoforms regulated by microRNAs
- need to target all 3
Repeat 3x the next slide on oncogenes and their mechanism of pro-angiogenic activity
Bcl-2
VEGF upregulation
Fos
VEGF upregulation
Jun
VEGF upregulation, thrombospondin downregulation
Wnt
Increased VEGF
p53
VEGF upregulation, thrombospondin downregulation
VHL
Increased VEGF
Rb
Decreased thrombospondin
Ras
VEGF upregulation, thrombospondin downregulation
What is VEGF and what does it do?
3 marks
- Ligand essential for tumour development
- Produced throughout tumour life cycle
- Isoform A can generate abnormal blood vessels
What does the VEGF family bind to respectively and what do they regulate?
3 marks
- VEGF A can bind to receptor VEGFR1 and VEGFR2
- VEGF C & D can bind to recptors VEGFR2 & VEGFR3
- Family regulates lymph angiogenesis as tissue sprouts and grows in the same way
Which is the most important VEGF isoform for tumourogenesis and angiogenesis?
1 mark
VEGF A
In what forms does the VEGF A isoform exist?
3 marks
- Different spliced variants that can bind to VEGFR1/2 and be cleaved by plasmid
- Differ in C-terminal where they bind heparin in ECM
- Heparin binding site determines if bind to ECM and how strong
Which variant of VEGF A do tumours produce the most and why?
3 marks
- VEGF variant 165:
- Can be free and bound to ECM
- Provide short and long range guidance for new molecules - can compensate for other two variants
What are the other 2 variants of VEGF A and why aren’t they produced as much as VEGF165?
6 marks
- VEGF121:
- Doesn’t bind heparin sulfate and freely diffusible
- Provide long range guidance for developing blood vessels
- VEGF189:
- Strongly bind heparan sulphate and ECM
- Provide short range guidance for developing blood vessels
VEGF165 - good mix of the two
How does a distinct release of bound VEGF to ECM occur in a tumour to start angiogenesis?
4 marks
- Pre-malignant cells don’t see increase in VEGF or VEGFR
- (7-12wk model) - cells switch on angiogenesis are malignant and growing
- Islet cells w/ excess proliferation send signal to bone marrow, which sends signal to macrophages then to islets
- Immunce cells release MMPs to cleave ECM bound VEGF and fragment will go to bind to VEGFR - isn’t increased in islets and trigger angiogenesis
What is the placental growth factor?
3 marks
- Normally confined to placenta but can be overexpressed in tumours
- Binds to VEGFR-1
- Can potentiate VEGF-A activity (by binding to VEGFR-1), s_timulates detachment of pericytes and activate pro-angiogenic genes_
What are VEGFRs?
1 mark
- Receptor tyrosine kinases that possess split kinase in intracellular domain
What is a split kinase?
1 mark
Additional kinase baove main kinase that doesn’t make them operate in any different way
What is VEGFR-1?
2 marks
- TRK weakly activated by VEGF-A but binds to it with strong affinity
- Postulated to be a decoy receptor as receptor 1 binds to VEGF
What is VEGFR-2?
2 marks
TRK strongly activated by VEGF-A weakly binds ligands
Overexpressed in tumour cells
Does PLGF bind to VEGFR-1 or VEGFR-2?
2 marks
- VEGFR-1
- If lots in tumour will bind to it leaving less receptor available to bind to VEGF-A
What are neuropilins?
2 marks
- Apart of VEGF R family
- Very short cytoplasmic tails and act as co-receptors for VEGF so VEGF a will bind neuropilin and will present ligand in way to VEGFR2
How is tumourigenic angiogenesis promoted by VEGF-A through VEGFR-2?
6 marks
- Signalling via VEGFA through VEGFR2 (165 variant)
- VEGFA dimeric ligand - get transphoshporylation of tyrosines on receptors
- Signalling promotes production of nitric oxide for dilation of BV
- RAS/MAP/Kinase promote endothelial cell proliferation
- For migration signal pormotes migration (from CDC42)
- Signalling via AKT will enhance cell survival by inhibiting apoptosis
