Genes Linked to Breast Cancer
Three genes have been linked to the occurrence of breast cancer. These three genes, called p53, BRCA-1 and BRCA-2, act as tumor suppressors. This means that their normal function is to control the cell division and make sure the cell does not start to divide uncontrollably by turning into a tumor cell. Mutations, or disorder of the normal sequence, in these genes leads to increased incidence of breast cancer. However, these mutations only account for about 10% of all breast cancer cases.
The Relevance of Family History of Breast and Ovarian Cancer
Mutations in the genes associated with breast cancer could either be inherited, passed on from either parent, or sporadic, occurring during the life of an individual. The mutation in BRCA-1 gene accounts for a very small percentage of breast cancer. However, women from the families with the history of breast cancer who inherit a mutated allele of BRCA-1 gene from either parent have an approximately 85 to 90 percent lifetime chance of developing breast cancer, as well as about a 33 percent chance of developing ovarian cancer. Nevertheless, not all mutations of BRCA-1 gene lead to the development of cancer. The chance of developing a sporadic mutation in BRCA-1 gene during one’s life, which may lead to breast cancer, is extremely low.
P53 mutations are present in approximately 40 percent of human breast cancers as an acquired defect. Other genes, aside from the tumor suppressors mentioned above could be involved in the sporadic case of breast cancer. One example is erbB2.
Genetic Screening For Breast Cancer
Since mutations in the BRCA-1 suppressor gene rarely occur sporadically, only women with family history of breast or ovarian cancer should be screened for mutations in these genes. Genetic tests are commercially available and are being applied in the community. However, BRCA1 screening is not sufficiently well understood yet, and is not recommended for the use outside of the research arena.
Breast cancer is one of the few types of cancers where screening by a mammogram improves survival. Annual screening after age 50 reduces the chances of dying from breast cancer by 25 to 30 percent. Though a subject of some controversy due to risks of radiation, annual mammogram is recommended for women over 40.