Cell growth + division lecture 9

Question 1

Oncogenes

Answer 1

Genes that contribute in a dominant manner to transformation of a cell
- Can be virally encoded or modified cellular genes

Question 2

Proto-oncogene

Answer 2

• Normal cellular counterpart of an oncogene

- Mutation of protoco-oncogene → oncogene

Question 3

Tumour formation multistep

Answer 3

• Loss of tumour suppressor + activation of oncogene

1. Loss of growth factor dependence
2. Intensity to anti-growth signals
3. Evasion of apoptosis
4. Genomic instability
5. Metabolic shift
6. Immortality
7. Sustained angiogenesis
8. Metastasis

Question 4

Ongene activation

Answer 4

• Point mutation
• Amplification
• Chromosomal inversion

Question 5

Identification of oncogenes

Answer 5

1. Tumour forming retroviruses
   - Class 1 cause rapid formation of tumours after infection
   - Multifunctional tumours
   - Oncogenes encode constitutively active versions of proteins
   - Virus picked up cellular genes
   - e.g. capture of src by ALV
   - Class II = slower onset
   - Monoclonal tumours
   - Virus integrates beside cellular gene
   - myc 2 hotspots for insertion?
2. Isolation from tumour derived DNA
   - Mutations in endogenous cellular genes
   - Take DNA + introduce in growth-factor dependent cells, take GF away + see what grow
   - A160 grow on top of one another
3. Chromosomal translocation
   - E.g. Abl + Myc
   - Can lead to removal of miRNA regulatory sequences e.g. translocations lead to loss of miRNA bs
4. Identification of genome amplification region
   - e.g. erb2 brest cancer
   - Use southern blotting to look at level

Question 6

Levels of oncogene action

Answer 6

1. Growth factors
   - E.g. sis
2. Growth factor receptor
   - Leads to constitutive activation
   - Activates ds signalling pathway, pass restriction point
   - Mutation or overexpression (↑ chance of dimer)
3. Signalling pathway protein
   - May only activate 1 branch
   - e.g. V-src lacks inhibitory phosphate
   - e.g. mutations that lock Ras in active state, residue 12 ↑ commonly mutated
   e. g. PI3K, mutations along protein, more likely to happen
4. TF
   - cycle progression needs new gene expression
   - identify IE genes (add serum to quiescent cells, use RNAseq to see change in expression)
   - Some IE genes are oncogenes which are themselves TF e.g. fos/jun