Oncogenes and Tumour Suppressor Genes

Question 1

viral oncogenes (v-onc)

Answer 1

copy of normal cell genes (c-onc) incorporated into viral particles - identification

Question 2

discover cell oncogenes by

Answer 2

analysis transduced cell gene seq in acute transforming retroviruses (neu)
identification of preferred integration sites of retroviruses (wnt1 mice)
characterisation of chromosomal translocations (BCR-ABL)
characterisation of amplified DNA sequence (NYMC)
direct gene transfer experiments to assay for biological activity of cell transforming genes (NRAS)
whole genome sequencing

Question 3

oncogene detection by DNA transfection

Answer 3

NIH 3T3 cells used as recipient - immortal not cancerous
oncogenes cause - foci formation (loss contact inhibition)
growth in semi-solid medium (loss anchorage dependence)
morphological abnormalities
reduced serum requirement
increased saturation dependency

Question 4

Oncogenes control growth by

Answer 4

secreted growth factors/ligands (SIS)
cell surface receptors (ERBB)
Intracellular signal transduction (RAS, ABL)
DNA-binding nuclear proteins/transcription factors (MYC/JUN)
cell regulatory proteins (MDM2, CDK) MDM2 act on G1S - divide quicker

Question 5

Mechanism of oncogene activation

Answer 5

Point mutation
Amplification
Translocation/ rearrangement

Question 6

Point mutation oncogene

Answer 6

hyperactive version - qualitative
HRAS - bladder, lung, colon, melanoma
KIT - GI, stromal

Question 7

amplification oncogene

Answer 7

quantitative - multiple copies on chromosome
ERBB2 - breast, ovarian, gastric, colon
NYMC - neuroblastoma (child)

Question 8

translocation/rearrangement oncogene

Answer 8

IGH-MYC - burkitts lymphoma - low expression gene put in high expression region
BCR-ABL - chronic myelogenous leukaemia - new protein

Question 9

Oncogene point mutation RAS family

Answer 9

signal transduction - G-protein

HRAS, KRAS, NRAS

Question 10

HRAS

Answer 10

murine Harvey sarcoma virus

Question 11

KRAS

Answer 11

Murine Keirsten sarcoma virus

Question 12

NRAS

Answer 12

neurblastoma

Question 13

1) Oncogenic RAS - ligand bind receptor

Answer 13

GTP bind RAS - signal transmission

Question 14

2) RAS GTPase actvity

Answer 14

GTP–>GDP = inactive

Question 15

3) Mutations at amino acid residues (12, 13, 61) (GTP binding)

Answer 15

Reduced GTPase activity

Question 16

4) Reduced GTP activity

Answer 16

GTP degraded slower + excessive signalling

Question 17

MAPK/ RAS-RAF-MEK-ERK Pathway (cause)

Answer 17

oncogenes ERBB, PDGFR, RAS, RAF

Question 18

MAPK leads to cancer by

Answer 18

overexpression gene in nucleus –> pro-proliferation

—> metastasis

Question 19

Oncogene activation by amplification

Answer 19

ERBB2
MYC
MDM2

Question 20

Oncogene amplification ERBB2

Answer 20

Breast , ovarian carcinoma - tyrosine kinase receptor (cell signalling)

Question 21

Oncogene amplification MYC

Answer 21

breast carcinoma - transcription factor pro-proliferative/apoptotic genes

Question 22

Oncogene amplification MDM2

Answer 22

sarcomas - negative regulator of p53 pathway

Question 23

Amplified regions exist as

Answer 23

Homogenously staining regions (HSRs)
Double minutes (DMs)

Question 24

Homogenously Staining regions

Answer 24

insertions within normal chromosomes (continuous, in tandem)

Question 25

Double Minutes

Answer 25

small paired chromatin bodies separate from chromosomes, spliced out

Question 26

Amplicon

Answer 26

unit of amplified genetic material

Question 27

MYCN detection

Answer 27

2 probes one for centromere of chromosome 2 and one for MYCN (2p), amplified 10-500 fold 25% neuroblastoma

Question 28

Oncogene activation translocation (novel chimeric gene)

Answer 28

escapes normal regulation, abnormal and transforming - common in leukaemias and lymphomas, identify by cloning

Question 29

Philadelphia chromosome (CML)

Answer 29

9;22 translocation 
9 breakpoint in intron of ABL oncogene
joins 5' region ABL to 3' region BCR on 22
tyrosine kinase related to ABL
always switched on

Question 30

Tyrosine kinase inhibitor for translocation

Answer 30

competitive inhibitor to ATP, which phosphorylates tyrosine kinase
specific - less toxic

Question 31

Oncogene activation - translocation to active region

Answer 31

Burkitts lymphoma - EBV/mosquito etiology

MYC activation - overexpression

Question 32

MYC translocations

Answer 32

t(8;14) (q24-q32)
t(8;22) (q24-q11)
t(2;8) (p12-q24)
MYC placed close to IGH locus - expressed high in lymphoid
H - 14q32
K - 2p12
L- 22q11

Question 33

Burkitts lymphoma

Answer 33

place oncogene in actively transcribed chromatin in antibody producing B cells

Question 34

Burkitts lymphoma - not MYC exon 1

Answer 34

removal of control sequence - overexpression MYC

Question 35

Burkitts lymphoma translocation cause

Answer 35

error in V-D-J gene rearranegment