Breast cancer genetics. BRCA1 and BRCA2: The main susceptibility genes.

Breast cancer is among the most common world cancers. In Mexico this neopla sm has been progressively increasing since 1990 and is expected to continue . The risk factors for this disease are age, some reproductive factors, ion izing radiation, contraceptives, obesity and high fat diets, among other fa ctors. The main risk factor for BC is a positive family history. Several fa milies, in which clustering but no mendelian inheritance exists, the BC is due probably to mutations in low penetrance genes and/or environmental fact ors. In families with autosomal dominant trait, the BRCA1 and BRCA2 genes a re frequently mutated. These genes are the two main BC susceptibility genes . BRCA1 predispose to BC and ovarian cancer, while BRCA2 mutations predispo se to BC in men and women. Both are long genes, tumor suppressors, function ing in a cell cycle dependent manner, and it is believed that both switch o n the transcription of several genes, and participate in DNA repair. The mu tations profile of these genes is known in developed countries, while in La tin America their search has just began. A multidisciplinary group most be responsible of the clinical management of patients with medications in BRCA 1 and BRCA2, and the risk assignment and Genetic counseling most be done ca refully.