| |
|
|
|
|
|
|||
|
|
|
MedicineWorld.Org - Cancer - BRCA1 and BRCA2 : Breast cancer associated genes
|
|
Several genetic mutations in have been associated with increased risk of development of breast cancer. The most common of these genetic mutations are called BRCA1 and BRCA2. Identification of these two genes has markedly improved our understanding of breast cancer genetics. In women with mutation in these genes the risk of development of breast cancer is markedly increased. Apart from increased risk of breast cancer, BRCA1 and BRCA2 mutations are associated with increased risk of variety of other cancer including ovarian cancer. Since BRCA1 and BRCA2 mutations may be associated with increased risk of development of breast cancer at younger age, hence when a young woman develops breast cancer this possibility should be explored especially with other family members affected with breast or ovarian cancer. Both BRCA1 and BRCA2 are inherited as autosomal dominant mode and can be passed to offspring by either paternal or maternal lineage.
In the general population the incidence of BRCA1 mutation is between 1 in 500 and 1 in 800. The incidence of BRCA2 mutation is even lower. Individuals with Ashkenazi Jewish background has an increased incidence of BRCA1 and BRCA2 mutations. 1 in 40 of individuals with Ashkenazi Jewish background may be affected with BRCA1 or BRCA2 mutation. The most common mutation in BRCA1 is called 185delAG. BRCA1 associated breast cancer tend to be high-grade and hormone receptor negative, however it is not clear if the overall out come is different from breast cancer not associated with BRCA mutations. BRCA2 associated breast cancer tend to resemble the regular mutation unrelated breast cancer. |
BRCA1 In 1990 BRCA1 was localized to chromosome 17 and the gene was cloned in 1994. Mutations in BRCA1 gene are associated with 50 percent to 85 percent life-time risk of developing breast cancer as seen in various studies. Carriers of BRCA1 gene mutation often develop breast cancer at a younger age compared to the general population. The risk of developing ovarian cancer is also elevated in carriers of BRCA1 mutation, but not to the level of increase in breast cancer risk. If a family has relatives with early onset breast cancer and ovarian cancer, the possibility of BRCA mutation should always be considered. Men with BRCA1 mutation generally do not have an increase risk of development of breast cancer, and this is in contrast to BRCA2 mutation which causes increased risk of breast cancer development in the male carriers as well. BRCA1 carriers including men are at a higher risk of developing colon cancer and the male carriers are at increased risk of developing prostate cancer. BRCA2 BRCA2 gene is located on chromosome 13. The risk of development of breast cancer in women carrying BRCA2 mutations are similar to the risk of BRCA1 carriers, however the risk of development of ovarian cancer is lower in BRCA2 mutation carriers compared to BRCA1 mutation carriers. Men carrying BRCA2 mutation have an increased risk of developing breast cancer and the lifetime risk for a male carrier is about 5 percent. Some studies have suggested that BRCA2 mutations are associated with increased risk of other types of cancers as well, but the information on this aspect is very limited to draw any conclusions. |
| BRCA1 and BRCA2 : Breast cancer associated genes |
