Genetics of Breast Cancer

What role do genes play in breast cancer ?
-One or more genes in the cell are mutated
-Creating an abnormal protein or no protein at all
-Information provided by the abnormal protein is different from that of the normal protein
-Cells multiply uncontrollably.


Types of Genetic Mutation
Germline mutation
-Born with a genetic mutation in all their cells
-Acquire a genetic mutation in a single cell during one’s lifetime.

Somatic mutation
-An acquired mutation is passed to all cells that develop from that single cell
-Cause by environmental factors
Eg. Cigarette smoking


Gene Mutation
-Occur in *tumor suppressor genes
*Make proteins that prevent tumor formation by limiting cell growth

-Mutation in the tumor suppressor gene
A loss of the ability to restrict tumor growth
Cancer develops.


Genes related to Breast Cancer

1) BReast CAncer gene 1 (BRCA1)
>Tumor suppressor cell

>Provides instruction in repairing damaged DNA.
~Natural and medical radiation
~Environmental exposures

>Regulate activities of other genes
>Involve in embryonic development
>Regulate cell division


How are changes in the BRCA1 gene related to health conditions ???
>Mutation
~Abnormally short version of BRCA1 protein
~Prevent protein from being made
~Change protein building blocks (amino acids)

~Delete large segment of DNA from BRCA1
*Unable to help repair damaged DNA
*Unable to fix mutation

Defects accumulate , allow cells to grow and divide uncontrollably.
Form TUMOR


Where is the BRCA1 gene located?
chromosome 17: base pairs 38,449,839 to 38,530,993 (photo will be shown on friday)

2) BReast CAncer gene 2 (BRCA2)
>Tumor suppressor cell

>Provides instruction in repairing damaged DNA.
*Natural and medical radiation
*Environmental exposures

>Maintaining the stability of a cell’s genetic information
>Regulate cytokinesis


How are changes in the BRCA2 gene related to health conditions ???

>Mutation
~Insert or delete a small number of DNA building blocks (nucleotides)
~*Fanconi anemia type D1 (FA-D1)
*when two faulty copies of the BRCA2 gene are present in each cell
-reduce the amount of the BRCA2 protein to very low levels.

>increased risk of ovarian cancer, prostate cancer, pancreatic cancer, fallopian tube cancer, male breast cancer, and an aggressive form of skin cancer called melanoma.


Where is the BRCA2 gene located?
chromosome 13: base pairs 31,787,616 to 31,871,804


3) CDH1
4) PTEN
5) STK11
6) TP53



How does a woman know if breast cancer runs in the family?
Breast cancer may run in the family if
first-degree relatives (mothers, sisters, children) /
many close relatives (first-degree relatives, grandmothers, aunts, nieces, grandaughters, cousins)
have been diagnosed with breast cancer, especially before age 50.


What is a woman's risk if breast cancer runs in the family?
>woman's first-degree relative developed breast cancer
woman’s risk is double the average woman's risk

>two first-degree relatives developed breast cancer
woman’s risk is 5 times the average risk

>uncertain how much a woman's risk of breast cancer is increased when a man in the family has breast cancer.

Link :
http://ghr.nlm.nih.gov/condition=breastcancer
http://www.cancer.net/patient/Learning+About+Cancer/Genetics/The+Genetics+of+Breast+Cancer