Oncogenes are genes that have the potential to cause cancer. They were originally normal proto-oncogenes that became activated through mutations or increased expression. The first confirmed oncogene, SRC, was discovered in 1970 in a chicken retrovirus. Proto-oncogenes stimulate cell division, inhibit differentiation, and prevent apoptosis. They can become oncogenes through point mutations, gene amplification, or chromosomal translocations. When activated, oncogenes result in uncontrolled cell growth and proliferation signals, leading to cancer. Maintaining a healthy lifestyle may help lower the risk of cancer-causing mutations in proto-oncogenes.

1. Oncogene
By:
Hemant Santosh Bothe
School of Life Sciences, SRTMU Nanded
M.Sc. Biotechnology Sem I

2. Introduction:
• An oncogene is a gene that has the potential to cause
cancer.
• In certain circumstances oncogene can transform a cell
into a tumor cell.
• A proto-oncogene is a normal gene that can become an
oncogene due to mutations or increased expression.
Proto-oncogene  “Mutation”  Oncogene
• The resultant protein encoded by an oncogene is
termed Oncoprotein.

3. History
• The first confirmed oncogene was discovered in
1970 and was termed SRC (pronounced “sarc” as
it is short sarcoma).
• SRC was first discovered as an oncogene in a
chicken retrovirus.
• Experiments performed by Dr. G. Steve Martin
of the University of California, Berleley
demonstrated that SRC was indeed the gene of
the virus that acted as an oncogene upon
infection.

4. Functions of Proto-Oncogene
Proto-oncogenes are a group of normal genes in a
cell. They contain the necessary information for
our body to make the proteins responsible for:
• Stimulating cell division
• Inhibiting cell differentiation
• Preventing apoptosis(cell death)
These processes are essential for cell growth and
development and for maintaining healthy tissues
and organs in body.

5. Activation
The proto-oncogene can become an oncogene by
a relatively small modification of its original
function. There are three basic methods of
activation:
• A mutation within a proto-oncogene, or within a
regulatory region( for example the promoter
region) can cause a change in the protein
structure.
• An increase in the amount of a certain protein
• A chromosomal Translocation

6. Examples of proto-oncogenes
Over 40 different proto-oncogenes have been
discovered in the human body. Example include:
Ras- The first proto-oncogene to be shown to turn
into an oncogene is called Ras.
HER2- Another well-known proto-oncogene
is HER2. This gene makes protein receptors that
are involved in the growth and division of cells in
the breast.

7. Myc- The Myc gene is associated with a type of cancer
called Burkitt’s lymphoma. It occurs when a
chromosomal translocation moves a gene enhancer
sequence near the Myc proto-oncogene.
Cyclin D – Cyclin D is another proto-oncogene. Its
normal job is to make a protein called Rb tumor
suppressor protein inactive.

8. Mechanisms of Oncogene
Activation
There are at least three different types of gain of
function mutations that can cause a proto-oncogene to
become an oncogene:
Point mutation: This mutation alters, inserts, or deletes
only one or a few nucleotides in a gene sequence, in
effect activating the proto-oncogene.
Gene amplification: This mutation leads to extra copies
of the gene.
Chromosomal translocation: This is when the gene is
relocated to a new chromosomal site that leads to
higher expression.

9. Result of Oncogenes
Activation
Over
production
of growth
factors
Flooding
of the cell
with
replicatio
n signals
Uncontrol
led
stimulati
on in the
intermedi
ary
pathways
Cell
growth by
elevated
levels of
transcript
ion
factors
Cancer

10. How can we takeway?
We can’t completely prevent a mutation from
happening in a proto-oncogene, but our lifestyle may
have an impact. We may be able to lower our risk of
cancer-causing mutation by:
• Maintaining a healthy weight
• Vaccinating against viruses that can lead to cancer,
such as hepatitis B and human papillomavirus (HPV)
• Eating a well-balanced diet packed with fruits and
vegetables
• Exercising regularly

11. • Avoiding tobacco products
• Limiting intake of alcohol
• Using sun protection when go outdoors
Even with the healthy lifestyle, changes can still
happen in a proto-oncogene. This is why
researchers are currently looking into oncogenes
as a major target for anticancer drugs.