|Approximately 5-10% of breast cancers are hereditary and are mainly due to mutations on the BRCA1 or BRCA2 genes. Mutations on these genes are responsible for approximately 50% of the cases of cancers in individuals with strong family history or diagnosis of cancer in young age.
There are also other syndromes that increase the risk of developing breast and other types of cancer such as the Li-Fraumeni Syndrome, the PTEN Syndrome and the Peutz-Jeghers Syndrome.
BRCA1 and BRCA2
The BRCA1 and BRCA2 genes are “Tumor-suppressor Genes” which means that the proteins that they produce (encode) play key role in the regulation of proliferation of cells through DNA repair. Mutations on one of these two genes cause deregulation and leads to uncontrolled proliferation of the cells and thus the creation of tumors. It is estimated that in the general population, 6-7% of the cases of breast cancer and 10% of the ovarian cancer cases are due to mutations on these genes.
Partner and Localizer of BRCA2 (PALB2) is another tumor-suppressor gene. The protein produced by this gene cooperates with the protein produced by BRCA2 in DNA damage repair and thus in the regulation of the proliferation of the cells. Recent studies in the USA have shown that mutations on this gene are found in 3-4% of the patients that were found negative for mutations on BRCA1 and BRCA2.
Compared to their relatives that did not have a mutation on the PALB2 gene, the mutation carriers had a 2.3 fold increase in the risk of developing breast cancer before the age of 55 and this risk goes up to 3.4 fold for developing breast cancer by the age of 85.
CHEK2 checkpoint homolog (CHEK2) is a protein whose normal form plays important role in the regulation of oncogenesis (cancer development) by deactivating the cells that have undergone damages until the DNA repair mechanisms are activated.
The deletion of a base on the 1100 locus of the CHEK2 gene is related to an increased risk of developing breast cancer and it is found in 3,7% of the patients.