20.3 Tumor Suppressor Genes

Question 1

act oppositely to oncogenes; inhibit cell proliferation and tumor development

Answer 1

tumor suppressor genes

Question 2

the first tumor suppressor gene identified, ()

Answer 2

Rb

Question 3

inherited mutation in Rb + a second somatic mutation resulted in the loss of the normal Rb allele → ()

Answer 3

development of retinoblastoma

Question 4

Rb serves as a () → loss of Rb gene leads to tumor development

Answer 4

negative regulator

Question 5

() was the second tumor suppressor protein identified

Answer 5

p53

Question 6

loss of p53 interferes with ()

Answer 6

induction of apoptosis

Question 7

summarize the normal function of p53

Answer 7

acts in response to DNA damage → induction of p53 activates transcription of proapoptotic and cell cycle inhibitory genes

Question 8

p53 activates the CKI (1), as well as the proapoptotic Bcl-2 family members (2)

Answer 8

1. p21
2. PUMA and Noxa

Question 9

loss of p53 interferes with induction of apoptosis, caused by the oncogene protein ()

Answer 9

MDM2

Question 10

() tumor suppressor gene encodes a lipid phosphatase the dephosphorylates PIP3

Answer 10

PTEN

Question 11

summarize the function of PTEN as a tumor suppressor gene involved in signal transduction

Answer 11

PTEN inhibits PI3K and Akt → leads to inhibition of cell survival and cell proliferation; acts oppositely to PI3K

Question 12

tumor suppressor gene () encodes for p16, which is a CKI that works to inhibit Cdk4,6/cycD complexes

Answer 12

INK4

Question 13

summarize the function INK4 as a tumor suppressor gene involved in cell cycle progression

Answer 13

• INK4 encodes for p16, which in turn inhibits Cdk4,6/cycD complexes
• inhibition of Cdk4,6/cycD complexes leads to decreased inhibition of Rb
• mutational inactivation of Rb removes a key negative regulator of the cell cycle

Question 14

function to maintain the integrity of the genome

Answer 14

stability genes

Question 15

examples of stability genes

Answer 15

1. BRCA1
2. BRCA2
3. ATM gene

Question 16

how do stability genes act as tumor suppressor genes

Answer 16

they prevent high mutation frequency in oncogenes or tumor suppressor genes

Question 17

genes coding for microRNAs (miRNAs) can act as tumor suppressor genes because ()

Answer 17

miRNAs serve as major regulators of gene expression in eukaryotes

Question 18

in general, miRNA expression in tumors is ()

Answer 18

low

Question 19

let-7 miRNA acts as a tumor suppressor by ()

Answer 19

silencing the expression of the oncogenes rasK and c-myc

Question 20

() acts as a tumor suppressor by silencing the expression of the oncogenes rasK and c-myc

Answer 20

let-7 miRNA

Question 21

large number of different mutations in tumor affect a small number of complementary pathways that regulate:

Answer 21

1. cell fate
2. cell survival
3. genome maintenance

Question 22

mutations in the ff pathways affect cell survival

Answer 22

1. cell cycle/apoptosis
2. RAS
3. PI 3-kinase
4. STAT
5. MAPK
6. TGF-beta

Question 23

mutations in the ff pathways affect cell fate

Answer 23

1. Notch
2. Hedgehog
3. APC
4. chromatin modification
5. transcriptional regulation