This document summarizes tumor suppressor genes. It begins by defining tumors and genes. Tumor suppressor genes code for proteins that act as brakes on cell division. When mutated, they can no longer slow cell growth, allowing cancer to develop. There are three main types of tumor suppressor gene functions: slowing cell division, repairing DNA damage, and inducing cell death. Famous tumor suppressor genes include RB, p53, BRCA1, and BRCA2. Mutations in these genes are associated with increased cancer risks. Understanding tumor suppressor genes helps explain why cancer therapies don't always provide a cure.

1. TUMOR SUPPRESSOR
GENES
PRESENTED BY
POOJA.P
MSC BIOCHEMISTRY 1ST SEM
GUIDED BY
DR. MAHADESH PRASAD
BIOCHEMISTRY DEPARTMENT
POOJA BHAGAVAT MEMORIAL MAHAJANA PG CENTER

2. INTRODUCTION
Tumor
development of abnormal cells that divide uncontrollably and
have the ability to infiltrate and destroy normal body tissue
Supressor
something that prevents the development or expression
Gene
The gene is considered the basic unit of inheritance and contain
the information needed to specify physical and biological
traits.Most genes code for specific proteins, or segments of
proteins, which have differing functions within the body.

3. Tumor suppressor genes are the genes that make proteins that
act like brakes within the cell.
when they turned on they actually prevent the cell from dividing
.
However, if a tumor suppressor gene is lost or mutated in a very
specific way so that it losses its activity, the cell can then start to
divide uncontrollably,and this contributes to the development of
cancer. They are also called as antioncogenes

5. TYPES OF FUNCTION
Mainly of three types
Telling cell to slow down and stop dividing
Repairing damage to cellular DNA that results from
dividing and could lead to cancer
Causing damaged cells to start a process called
programmed cell death ,or apoptosis.

6. Analogy to driving:tumor suppresor gene are the brake
accelerator is oncogenes
Each cell [car] has an accelerator and brakes. In normal cars, both are
working fine. Multiple processes make sure they stay in balance so the
car both moves along steadily, but doesn't crash.
Cancer begins with a series of mutations in genes. Genes function as a
blueprint for making proteins with different functions.
Cancer can be related to problems with either the accelerator or the
brakes, but often, damage to both oncogenes and tumor suppressor
genes occurs before cancer develops. In other words, the accelerator
has to be stuck to the floor AND the brakes have to malfunction. The fact
that cancer often requires a number of different mutations is, in part,
why cancer is more common in older people.

7. Two Basic Roles of Tumor Suppressor
Genes
Gatekeepers and Caretakers
tumor suppressor genes may function as the "brakes" of the
car in three primary ways bY inhibiting cell growth, fixing
broken DNA, or causing a cell to die. These types of tumor
suppressor genes can be thought of as "gatekeeper" genes.
Yet some tumor suppressor genes function in more of a
caretaker role. These genes create proteins that oversee and
regulate many of the functions of other genes to maintain the
stability of DNA.

8. EXAMPLES
Tumor suppressor genes were first identified among children with
retinoblastoma[RB suppresor gene] . In retinoblastoma, in contrast
to many tumor suppressor genes, the tumor gene that is inherited
is dominant—and therefore allow cancers to develop in young
children. If one parent carries the mutated gene, then 50 percent
of their children will inherit the gene and be at risk for
retinoblastoma.

9. RETINOBLASTOMA

10. p53 gene : The guardian of Genome
The p53 gene creates protein p53 which regulates gene repair
in cells.
Mutations in this gene are implicated in around 50 percent of
cancers.
Inherited mutations in the p53 gene are much less common
than acquired mutations and result in the hereditary condition
known as Li Fraumeni syndrome.
The p53 codes for proteins that tell cells to die if they are
damaged beyond repair, a process referred to as apoptosis.

12. • BRCA1/BRCA2 genes: These genes are responsible for around
5 percent to 10 percent of breast cancers, but both BRCA1
gene mutations and BRCA2 gene mutations are associated
with an increased risk of other cancers as well. (BRCA2 is also
linked to an increased lung cancer risk in women.)
• APC gene: These genes are associated with an increased risk of
colon cancer in people with familial adenomatous polyposis.
Rb, APC, and p53 function as gatekeepers. In contrast,
BRCA1/BRCA2 genes function more as caretakers and regulate
the activity of other proteins involved in cell growth and repair.

13. SIGNIFICANCE
Understanding tumor suppressor genes may
also help explain a bit why therapies,
such as chemotherapy, don't completely
cure cancer. Some cancer treatments work
to stimulate cells to commit suicide.
Since some tumor suppressor genes trigger
the process of apoptosis (cell death),
when they aren't working properly, the
cancer cells may not be able to go through
the process of apoptosis as other cells

14. Reference
Molecular and cell biology of cancer
by Rita Fior and Rita Zilhao
Molecular biology of cancer
Lauren pecorino 4th edition
Article –why Tumor suppressor genes are important in cancer
by Lyne Eldridge , MD.