Chapter 4

Cellular Oncogenes

- 4.2 ~ 4.6 -

Many retroviruses carrying oncogenes have been found in chickens and mice

However, attempts undertaken during the 1970s to isolate viruses from most types of human tumors were unsuccessful.

Even reverse transcriptase-containing virus particles are difficult to find in human tumor samples.

Figure 4.2 (part 1 of 2) The Biology of Cancer (© Garland Science 2007)

Sidebar 4.2

(NIH3T3 cells)

4.2 Transfection of DNA provides a strategy for detecting nonviral oncogenes

transformed by 3-methycholanthrene

Figure 4.2 (part 2 of 2) The Biology of Cancer (© Garland Science 2007)

(NIH3T3 cells)

DNA from tumor cells

The DNA from chemical-transformed tumor cells was able to convert non-tumorigenic NIH3T3 fibroblasts into tumorigenic cells.

Figure 4.3 The Biology of Cancer (© Garland Science 2007)

Transfection of DNA from T24 human bladder carcinoma cell line into NIH3T3 cells

DNA from human cancers also cause focus formation

cells in the focus surrounding untransformed monolayer cells

focus formation

4.3 Oncogenes discovered in human tumor cell lines are related to those carried by transforming retroviruses

Southern blotting (DNA) Northern blotting (RNA)

Figure 4.4 (part 2) The Biology of Cancer (© Garland Science 2007)

nitrocellulose paper

( 32P-DNA)

Figure 4.4 (part 3) The Biology of Cancer (© Garland Science 2007)

Figure 4.5 The Biology of Cancer (© Garland Science 2007)

______________________________11 (a ~ k) NIH3T3 cell lines transfected

with DNA extracted from a human bladder carcinoma cell line

untransfected NIH3T3

Homology between transfected oncogenesand retroviral oncogenes

probe used: H-ras oncogene present in Harvey rat sarcoma virus

Table 4.1 The Biology of Cancer (© Garland Science 2007)

TK : tyrosine kinase

Figure 4.6a The Biology of Cancer (© Garland Science 2007)

Amplification of the erbB2/HER2/neu oncogene in breast cancers

Kaplan-Meier plot

Figure 4.6c The Biology of Cancer (© Garland Science 2007)

erbB2/neu oncogene is amplified

erbB2/neu mRNA is overexpressed

increased level of erbB2/neu-encoded protein

erbB2/HER2/neu oncogene can be amplified or overexpressed in human breast carcinoma cells

Figure 4.8 The Biology of Cancer (© Garland Science 2007)

Cloning of transfected human oncogenes

Alu sequence - present in about 106

copies scattered throughout human genome

Figure 4.9 The Biology of Cancer (© Garland Science 2007)

Localization of the mutation responsible for oncogene activity

cloned DNA of a human

bladder carcinoma oncogene

Figure 4.10 The Biology of Cancer (© Garland Science 2007)

A point mutation is responsible for H-ras oncogene activation

4.4 Proto-oncogenes can be activated by genetic changes affecting either protein expression or structure

Figure 4.11a The Biology of Cancer (© Garland Science 2007)

homogeneous staining regions (HSR)

4.5 The myc oncogene can arise via at least three distinct mechanisms

The N-myc gene amplification is found in 30% of human childhood neuroblastoma.

Astrocytoma, retinoblastoma and small-cell lung carcinomas (neuroendocrinal traits) also often exhibit amplified N-myc genes.

* N-myc is a close relative of c-myc.

Kaplan-Meier plot of childhood neuroblastomaev

ent -

free

sur

viva

l

Table 4.3 The Biology of Cancer (© Garland Science 2007)

Activation of the myc protooncogenes 1. Gene amplification 10 ~ 30 copies or 100 ~ 150 copies

shown as homogeneously staining regions (HSR) or double minutes (DM)

2. Provirus integration - insertional mutagenesis

constitutive expression by insertion of retroviruses

3. Chromosomal translocation

Figure 3.23b The Biology of Cancer (© Garland Science 2007)

transcription of myc gene is controlled by viral promoters

excessive myc protein

Insertional mutagenesis

Figure 4.12 The Biology of Cancer (© Garland Science 2007)

Burkitt’s lymphoma in Africa

(Aedes simpsoni)

Malarial infection Epstein-Barr virus (EBV) genome in Burkitt’s lymphoma cells

Figure 4.13a The Biology of Cancer (© Garland Science 2007)

Chromosome translocations in Burkitt’s lymphoma

The expression of c-myc gene is placed under control of the trancription-controlling enhancer sequences of an immunoglobulin heavy chain (IgH) gene.

Figure 4.13b The Biology of Cancer (© Garland Science 2007)

Genetic map of the translocation event of c-myc gene

The c-myc gene is translocated into chromosome 8, under the control of the immunoglobulin heavy-chain (IgH) sequences present on human chromosome 14

Table 4.4 The Biology of Cancer (© Garland Science 2007)

Figure 4.14 The Biology of Cancer (© Garland Science 2007)

4.6 A diverse array of structural changes in proteins can also lead to oncogene activation

(GF)

Figure 2.23a The Biology of Cancer (© Garland Science 2007)

Philadelphia chromosome (Ph1)

The great majority (> 95 %) of chronic myelogenous leukemia (CML) has t(9; 22) (q34; q11) translocation

Figure 4.15a The Biology of Cancer (© Garland Science 2007)

Formation of the bcr-abl oncogene after t(9; 22) (q34; q11) translocation

(Abelson murine leukemia virus)

(breakpoint cluster region)

Figure 4.15b The Biology of Cancer (© Garland Science 2007)

Different breakpoints in bcr results in different types of human leukemia

acute lymphocytic leukemia

chronic myelogenousleukemia

chronic neutrophilic leukemia

↓a ↓b ↓c

↓

↓

Abl↑

a. b.c.

Bcr

Bcr-Abl fusion protein

Table 4.5 The Biology of Cancer (© Garland Science 2007)

Notations used for proto-oncogenes and oncogenes

gene protein

Non-human src, myc Src, Myc(chicken, mouse, etc.)

Human SRC, MYC SRC, MYC