Tumor Suppressor Genes

Question 1

normal function of p53

Answer 1

regulates cell cycle progression from G1 to S phase (checks for DNA mutations –> if there are, causes repair or promotes apoptosis)

Question 2

how many copies of p53 must be knocked out for tumor formation

Answer 2

both (knudson’s 2 hit hypothesis)

Question 3

syndrome caused by inherited mutation of p53

Answer 3

Li-Fraumeni syndrome

Question 4

normal function of Rb

Answer 4

regulates progression from G1 to S phase (holds on to E2F –> releases to go from G1 to S)

Question 5

what normally phosphorylates Rb?

Answer 5

cyclin D/CDK4 complex

Question 6

what transcription factor gets released when Rb is phosphorylated?

Answer 6

E2F

Question 7

what happens where there is a mutation in Rb?

Answer 7

constitutively free E2F –> unregulated cell cycle progression to S phase

Question 8

cancer associated with sporadic mutation of Rb

Answer 8

unilateral retinoblastoma

Question 9

cancer associated with germline mutation of Rb

Answer 9

bilateral retinoblastoma, osteosarcoma

Question 10

how many copies of Rb must be knocked out for tumor formation

Answer 10

both (Knudson’s two hit hypothesis)

Question 11

normal function of bcl2

Answer 11

stabilizes mitochondrial membrane, prevent release of cytochrome c (which would cause apoptosis)

Question 12

cancer associated with overexpression of bcl2

Answer 12

follicular lymphoma

Question 13

mechanism of follicular lymphoma

Answer 13

t(14;18) - translocation between bcl2 and IgH –> overexpression of bcl2 –> failure of apoptosis of B-cells in follicle of lymphnodes

Question 14

enzyme that is usually upregulated in cancer to prevent senescence

Answer 14

telomerase

Question 15

angiogenic growth factors commonly produced by cancers to promote angiogenesis

Answer 15

FGF, VEGF

Question 16

common mechanism by which tumor cells avoid immune surveillance

Answer 16

downregulate MHC I