An oncogene is a mutated gene that has the potential to cause cancer. Before an oncogene becomes mutated, it is called a proto-oncogene, and it plays a role in regulating normal cell division. Cancer can arise when a proto-oncogene is mutated, changing it into an oncogene and causing the cell to divide and multiply uncontrollably. Some oncogenes work like an accelerator pedal in a car, pushing a cell to divide again and again. Others work like a faulty brake in a car parked on a hill, also causing the cell to divide unchecked. Tumor suppressor genes are normal genes that slow down cell division or tell cells to die at the right time (a process known as apoptosis or programmed cell death). When tumor suppressor genes don't work properly, cells can grow out of control, which can lead to cancer.

1. Oncogenes and Tumor
suppresser gene
By, vaishnavi kaduba janjal
Pharm d 3rd year
Government college of pharmacy aurangabad

2. Oncogenes
Concept:
An oncogene is a gene that when mutated or expressed at
abnormally-high levels contributes to converting a normal cell
into a cancer cell.
1. In normal cells, proto-oncogenes code for the proteins that send a
signal to the nucleus to stimulate cell division.
2. These signaling proteins or molecules act in a series of steps called
signal transduction cascade.
3. Oncogenes are altered versions of the proto-oncogenes that code
for these signaling molecules.
4. The oncogenes activate the signaling cascade continuously,
resulting in an increased production of factors that stimulate
growth.

3. Proto-oncogenes
1. A gene involved in normal cell growth.
2. Mutations (changes) in a proto-oncogene may
cause it to become an oncogene, which can cause
the growth of cancer cells.
3. Proto-oncogene is responsible for the
transmission factor, growth factors, receptors
,protein formation.
4. Proto-oncogenes → oncogenes
Gene in normal cell point mutation new mutated gene

4. Functions of proto-oncogenes
Proto-oncogenes have been identified at all levels of the various signal
transduction cascades that control cell growth, proliferation and
differentiation:
1. extracellular proteins function as growth factors,
2. membrane proteins as cell surface receptors
3. cellular proteins that relay signals
4. proteins in nucleus, which activate the transcription and promote the
cell cycle
This signaling process involves a series of steps that:
• begin from the extracellular environment to cell membrane;
• involve a host of intermediaries in the cytoplasm;
• end in the nucleus with the activation of transcription factors
that help to move the cell through its growth cycle.

6. Tumor suppressor gene
1. A tumor suppressor gene acts, in a normal cell, to restrain the rate of
cell division. Tumor suppressor genes cause cells to become
cancerous when they are mutated to become inactive.
2. Tumor suppressor gene is also called as a Anti-oncogenes or recessive
oncogene
3. Tumor suppressor genes often function to restrain inappropriate cell
growth and division, as well as to stimulate cell death to keep our
cells in proper balance.
4. In addition, some of these genes are involved in DNA repair
processes, which help prevent the accumulation of mutations in
cancer-related genes
5. T.s.g. have two qualities a) gatekeeper
b) caretaker

7. P53 gene
• p53, also known as TP53 or tumor protein is a gene that codes for a protein that
regulates the cell cycle and hence functions as a tumor suppression.
• It is very important for cells in multicellular organisms to suppress cancer.
• P53 has been described as "the guardian of the genome", referring to its role in
conserving stability by preventing genome mutation
• The human p53 gene is located on the seventeenth chromosome
• It plays an important role in cell cycle control and apoptosis. Defective p53
could allow abnormal cells to proliferate, resulting in cancer.
• In normal cells, the p53 protein level is low. DNA damage and other stress
signals may trigger the increase of p53 proteins, which have three major
functions: growth arrest, DNA repair and apoptosis (cell death)
• Some important examples are listed below.
• Growth arrest: p21, Gadd45, and 14-3-3s.
• DNA repair: p53R2.
• Apoptosis: Bax, Apaf-1, PUMA and NoxA.

12. Thank you 💜