Approximately 5 to 10 percent of all cases of breast cancer are hereditary and associated with inherited gene mutations. Hereditary breast cancers tend to develop early in a woman’s life and are more likely to affect both breasts. Researchers have identified a correlation between variations in specific genes and the increased risk for developing breast cancer.
BRAC1 and BRAC2
Everyone has the BRAC1 (Breast Cancer Gene 1) and BRAC2 (Breast Cancer Gene2). These two genes function to repair cell damage and maintain the normal growth of breast cells. Women with certain mutations of these genes as well as men with BRAC1 mutations have an increased risk for developing breast cancer. Researchers are learning that additional mutations in areas of chromosomes called SNPs (single nucleotide polymorphisms) may predispose women with and without BRAC1 mutations to developing breast cancer.
CDHI
Other gene mutations, though rare and of lesser risk than BRAC1 and BRAC2 variations, have been identified. The CDHI gene makes a protein that helps cells bind together to form tissue. Research has shown that women with a CDHI mutation have an increased risk for developing invasive lobular breast cancer. Invasive lobular breast cancer begins in the milk producing glands or lobules of the breast. The cancerous cells then spread to other parts of the body.
CHEK2
The CHEK2 gene produces a protein which stops tumor growth. A prospective study of 9,231 Danish women revealed that a mutation of the CHEK2 gene is associated with a three-fold risk of breast cancer in women in the general population. Leader researcher, M. Weischer, and colleagues reviewed the 34 year observation records of the initial test group and conducted a case-controlled study of 5,766 participants.
PTEN
The PTEN gene produces a protein, which regulates cell growth and acts as a tumor suppressor. Mutations in the PTEN gene increase the risk for developing breast cancer as part of a rare hereditary cancer syndrome called Cowden syndrome.
ATM
The ATM gene produces a protein, which controls the rate at which cells grow and divide. It also assists cells in recognizing and repairing damaged DNA. Researchers have found that individuals who have a mutation in one copy of the ATM gene in each cell have an increased risk for developing breast cancer. The risk escalates for people who have at least one family member with ataxia-telangiectasis, which is a disorder resulting from mutations in both copies of the ATM gene in each cell.
TP53
The TP53 gene plays a role in the synthesis of a protein called tumor p53, which acts as a tumor suppressor. Mutations of the TP53 gene greatly increases the risk for developing breast cancer associated with a rare inherited cancer called Li-Fraumeni syndrome.
STK11
The STK11 gene is instrumental in the making of an enzyme called serine/threonine kinase 11, which is a tumor suppressor. Mutations in this gene lead to a rare inherited cancer disorder called Peutz-Jeghers syndrome. Variations in the STK11 increase the risk of developing breast cancer, but account for only a small fraction of all cases.
Sources:
Genetic Conditions: Breast Cancer: Genetics Home Reference, Sept. 6, 2011
http://ghr.nlm.nih.gov/condition/breast-cancer
Genetics: BreastCancer.org., Sept. 7, 2011
http://www.breastcancer.org/risk/factors/genetics.jsp
Google Books: Focus on Breast Cancer by Andrew P. Yao, 2004, Sept. 7, 2011
http://books.google.com/books?id=8iDY6lEfeGoC&pg=PA51&lpg=PA51&dq=cdhi+genes&source=bl&ots=driQwhFHap&sig=PHkv-rsKtJwduYePyw
Increased Risk of Breast Cancer Associated with CHEK2*1100delC: Journal of Clinical Oncology,
January 1, 2007, volume, M. Weischer, et al. Sept. 7, 2011
http://www.ncbi.nlm.nih.gov/pubmed/16880452?dopt=AbstractPlus
Genes: PTEN: Genetics Home Reference, Sept. 7, 2011
http://ghr.nlm.nih.gov/gene/PTEN
Genes: ATM: Genetics Home Reference, Sept. 7, 2011
http://ghr.nlm.nih.gov/gene/ATM
Genes: TP53: Genetics Home Reference, Sept. 7, 2011
http://ghr.nlm.nih.gov/gene/TP53
Genes: STK11: Genetics Home Reference, Sept 7, 2011
http://ghr.nlm.nih.gov/gene/STK11
Reviewed September 7, 2011
by Michele Blacksberg R.N.
Edited by Malu Banuelos