Transcript Biology of Cancer - Tunghai University

Chapter 4
Cellular Oncogenes
- 4.2 ~ 4.6 -
Mar 22, 2007
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.
4.2 Transfection of DNA provides a strategy
for detecting nonviral oncogenes
(NIH3T3 cells)
transformed by
3-methycholanthrene
Sidebar 4.2
Figure 4.2 (part 1 of 2) The Biology of Cancer (© Garland Science 2007)
DNA from tumor cells
(NIH3T3 cells)
The DNA from chemical-transformed
tumor cells was able to convert
non-tumorigenic NIH3T3 fibroblasts
into tumorigenic cells.
Figure 4.2 (part 2 of 2) The Biology of Cancer (© Garland Science 2007)
DNA from human cancers also cause focus formation
focus formation
cells in the focus
surrounding untransformed
monolayer cells
Transfection of DNA from T24 human bladder
carcinoma cell line into NIH3T3 cells
Figure 4.3 The Biology of Cancer (© Garland Science 2007)
4.3 Oncogenes discovered in human tumor cell lines are
related to those carried by transforming retroviruses
Southern blotting (DNA)
Northern blotting (RNA)
nitrocellulose
paper
( 32P-DNA)
Figure 4.4 (part 2) The Biology of Cancer (© Garland Science 2007)
Figure 4.4 (part 3) The Biology of Cancer (© Garland Science 2007)
Homology between transfected oncogenes
and retroviral oncogenes
probe used: H-ras oncogene present in
Harvey rat sarcoma virus
______________________________
11 (a ~ k) NIH3T3 cell lines transfected
with DNA extracted from
a human bladder carcinoma cell line
Figure 4.5 The Biology of Cancer (© Garland Science 2007)
untransfected NIH3T3
TK : tyrosine kinase
Table 4.1 The Biology of Cancer (© Garland Science 2007)
Amplification of the erbB2/HER2/neu
oncogene in breast cancers
Kaplan-Meier plot
Figure 4.6a The Biology of Cancer (© Garland Science 2007)
erbB2/HER2/neu oncogene can be amplified or
overexpressed in human breast carcinoma cells
erbB2/neu oncogene is
amplified
erbB2/neu mRNA is
overexpressed
increased level of
erbB2/neu-encoded protein
Figure 4.6c The Biology of Cancer (© Garland Science 2007)
Cloning of transfected human oncogenes
Alu sequence present in about 106
copies scattered
throughout human
genome
Figure 4.8 The Biology of Cancer (© Garland Science 2007)
Localization of the mutation responsible
for oncogene activity
cloned DNA
of a human
bladder
carcinoma
oncogene
Figure 4.9 The Biology of Cancer (© Garland Science 2007)
A point mutation is responsible
for H-ras oncogene activation
Figure 4.10 The Biology of Cancer (© Garland Science 2007)
4.4 Proto-oncogenes can be activated by genetic changes
affecting either protein expression or structure
4.5 The myc oncogene can arise via at least three
distinct mechanisms
homogeneous staining
regions (HSR)
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.
Figure 4.11a The Biology of Cancer (© Garland Science 2007)
event - free survival
Kaplan-Meier plot of childhood neuroblastoma
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
Insertional mutagenesis
transcription of myc gene is
controlled by viral promoters
excessive myc protein
Figure 3.23b The Biology of Cancer (© Garland Science 2007)
Burkitt’s lymphoma in Africa
(Aedes simpsoni)
Malarial infection
Figure 4.12 The Biology of Cancer (© Garland Science 2007)
Epstein-Barr virus (EBV) genome
in Burkitt’s lymphoma cells
Chromosome translocations
in Burkitt’s lymphoma
The expression
of c-myc gene is
placed under
control of the
trancriptioncontrolling
enhancer
sequences of an
immunoglobulin
heavy chain
(IgH) gene.
Figure 4.13a 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
Figure 4.13b The Biology of Cancer (© Garland Science 2007)
Table 4.4 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 4.14 The Biology of Cancer (© Garland Science 2007)
The great majority (> 95 %) of chronic myelogenous
leukemia (CML) has t(9; 22) (q34; q11) translocation
Philadelphia chromosome (Ph1)
Figure 2.23a 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 4.15a The Biology of Cancer (© Garland Science 2007)
Different breakpoints in bcr results in
different types of human leukemia
↓
↓a
↓b ↓c
↓
a.
acute lymphocytic
leukemia
b.
c.
Bcr
↑
Abl
Bcr-Abl fusion protein
Figure 4.15b The Biology of Cancer (© Garland Science 2007)
chronic myelogenous
leukemia
chronic neutrophilic
leukemia
Table 4.5 The Biology of Cancer (© Garland Science 2007)
Notations used for proto-oncogenes and oncogenes
Non-human
(chicken, mouse, etc.)
Human
gene
protein
src, myc
Src, Myc
SRC, MYC
SRC, MYC