Transcript Environmental Carcinogenesis

a M.I.N.Y. MOUSE Production:
Munasha, Ivan, Noor, Yuna
Also featuring: Stephen M. and Julie R.
What broad category of genes is involved with
carcinogenesis? How would you describe the
function of these genes in normal cells and in
cancer cells?
The broad category of genes involved with
carcinogenesis includes oncogenes and
tumor suppressing genes (along with subcategorical genes such angiogenic genes and
metastasis genes).
The function of these genes in normal cells and
in cancer cells depends on the specific genes,
and their function in normal cells differs
completely from their function in cancer cells.

A normal gene cell transforms into a cancer cell
once genes that regulate cell growth and
differentiation are altered.
 These genetic changes may include the gain or loss of
entire chromosomes, or the mutation of a DNA
nucleotide.
▪ It takes, however, a series of mutations on only a certain
number of genes for a normal cell to become cancerous.
 During the development of a malignant tumor, DNA
damage occurs as an accumulation of mutations in as
many as six or more genes.

Two types of genes are affected by these
genetic changes: oncogenes and tumor
suppressing genes (these genes also play
important roles in tumor development).

In normal cells:
 A proto-oncogene codes for proteins that
stimulate cell division.

In cancer cells:
 When a mutation occurs in a proto-oncogene, it
can become a carcinogenic oncogene that causes
these proteins to be overactive, resulting in the
formation of large numbers of cells.


Proto-oncogenes: They promote cell growth
and mitosis in a variety of ways; many can
produce hormones between cells that
encourage mitosis.
Oncogenes: They are analogous to an
accelerator on a car in that they cause the rate of
cell division to increase. Oncogenes may be
altered genes (mutations of proto-oncogenes) or
normal genes expressed at inappropriately high
levels. When oncogenes are present, the
phenotype of cancer cell development will be
expressed.
Proliferation:
Rapid reproduction of a cell

In normal cells:
 Tumor suppressor genes code for proteins that
inhibit cell division.

In cancer cells:
 When a mutation occurs in a tumor suppressor
gene, the inhibitory proteins may not function
properly, and inappropriate growth of cells (which
can be caused by the oncogene, for example)
remains unchecked.

Tumor suppressor genes can prevent cells
with damaged DNA from multiplying until
the damaged DNA is repaired.
 If the damage cannot be repaired, the gene would
allow for apoptosis (cell suicide) to remove the
threat it poses in the organism.

These genes are often disabled by cancerpromoting genetic changes, which would
then lead to the growth of cancer cells.


Angiogenic genes control the creation of blood vessels.
Although they are vital towards growth, development,
and wound healing, they actually help tumors to transition
from a dormant state to a malignant one.
 This lead to the use of angiogenesis inhibitors (some are a
normal part of the body's control, some are administered as
drugs).

The tumors increase in size because angiogenic genes
provide a constant supply of blood to the tumor, meaning
less water, oxygen and vitamins will be reaching the
healthy tissues. This higher nutrient supplies means that
cancer cells are less likely to die, thus maintaining the
tumor’s size.

Since metastasis is the spread of a disease
from one organ or part to another nonadjacent organ or part, metastasis genes
control where such cells go. These genes are
the ones that would allow cancer cells to
spread to other parts of the body.

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http://envirocancer.cornell.edu/Factsheet/Ge
netics/fs6.TSgenes.cfm
http://www.enotes.com/carcinogenesisreference/carcinogenesis-172934
http://www.cancer.org/Cancer/CancerCauses/
OtherCarcinogens/GeneralInformationabout
Carcinogens/known-and-probable-humancarcinogens