Tumour suppressors

Question 1

What do tumour suppressor genes regulate?

Answer 1

Cell cycle, DNA repair and apoptosis

Question 2

What happens when tumour suppressor genes are inactivated?

Answer 2

Cancer arises
Allows unchecked cell division
Abnormal replication
If both copies of TSG are inactivated or mutated it removes a natural ‘brake’ on the cell cycle => indirectly drives cancer
P53 normally stops abnormal cells - when mutated p53 cannot do its job and damaged cells divide unchecked

Question 3

What is the function of TSGs?

Answer 3

Help maintain cells in G0 phase or control progression through checkpoints (G1,G2, M)
Inhibit cell growth, promote DNA repair and trigger cell death

Question 4

What functions to mutations in TSG gain?

Answer 4

Promote cell survival
Support angiogenesis (blood vessel growth)
Encourage metastasis
Known as a ‘mutant p53 gain of function’ - acts like a oncogene

Question 5

Where do germ cell cancers originate from?

Answer 5

Sperm/ egg-producing cells
Common types - yolk-sac, teratomas, embryonal carcinomas

Question 6

What is retinoblastoma?

Answer 6

Caused by RB1 loss often inherited
Tumours in retinal cells due to loss of pRb regulation

Question 7

What is the most commonly mutated gene in cancer (>50%)?

Answer 7

p53