BRCA1 and BRCA2 genes are well known breast cancer genes and inherited mutations in these genes increase the risk of breast and ovarian cancers. Breast cancer, the most common, invasive cancer in females worldwide can run in families or occur in women without a prior family history of breast cancer. However, mutations in BRCA1 and BRCA2 account for only 20 to 25 percent of hereditary breast cancers and 5 to 10 percent of all breast cancers. Recent reports indicate that examining a broader range of breast and ovarian cancer-causing mutations are facilitating identification of new cancer-associated genes.
Breast Cancer in the Media
Angelina Jolie thrust genetic testing for breast cancer into the spotlight when she revealed in a New York Times Op-Ed article in May, this year, that she possessed breast cancer-associated mutations, which prompted her to undergo a double mastectomy.
Myriad Genetics, a genetic-testing company in Salt Lake City, Utah was the sole provider of commercial diagnostic testing on BRCA1 and BRCA2, with its patented BRACAnalysis test, the only route for determining predisposition to breast cancer.
In June, this year, the US Supreme Court struck down Myriad Genetics patents on BRCA1 and BRCA2, unanimously declaring that human DNA is “a product of nature” and thus “not patent eligible.” This decision ended a long-running legal challenge to the gene patents held by Myriad Genetics.
The past few months have bought a number of significant research and commercial development in the field of breast cancer diagnostic testing. Genetic testing allows patients at risk of contracting a specific disease to pre-emptively take action. Diet, exercise, medications, and surgery can be used to mitigate disease risk. In the case of breast cancer, diet and exercise are relatively weak risk factors, the main clinical decision concern pre-emptive removal of both breasts and/or ovaries and the use of tamoxifen to manage the risk.
Types of Breast Cancer Genes
Most cases of breast cancer occur by chance while a smaller percentage cluster in families. Hereditary breast cancers, those associated with inherited gene mutations, tend to occur earlier in life than non inherited or sporadic cases and are more likely to involve both breasts. Besides BRCA1 and BRCA2, mutations in other genes like the DNA repair genes, ATM and CHEK1 and syndromic genes like TP53 are associated with breast cancer.
At the 2013 Annual Meeting of the American Society for Human Genetics, Tomas Walsh of University of Washington reported on a targeted gene panel, the ‘BROCA breast cancer gene mutation’ test developed at UW. The test was developed and validated by Walsh and Mary-Claire King in 2010, and it has become widely available after the US Supreme Court struck down claims on patents held by Myriad Genetics on the BRCA1 and BRCA2 genes. The BROCA panel includes some 40 breast cancer genes.
Tom Walsh and colleagues examined nearly 750 families with a history of breast cancer in which at least one member had undergone commercial testing and received a negative result. The BROCA breast cancer gene mutation test panel helped determine the genetic root of disease in 25% of these families. The researchers even identified women who had received negative test results from Myriad Genetics’ BRACAnalysis test, who, in fact, had BRCA1 and BRCA2 mutations that BRACAnalysis did not pick up.
About a third of the families, whose genetic cause for breast cancer could be resolved, had mutations in genes like CHEK2, PALB, or TP53. The role of these genes in inherited cancers has been established while 20% of the families had mutations in genes that have been linked to breast cancer but not fully characterized — the researchers called these the ‘emerging risk’ genes.
The BROCA test has been performed on some 6,000 research participants and 500 clinical patients and there is a study underway using the BROCA panel to examine 7,000 cases and 5,000 controls to further study the ‘emerging risk’ genes.
In addition to the BROCA test panel, genome sequencing technologies like exome-sequencing enable comprehensive assessment of breast cancer, as well as ovarian, colon and other types of solid cancers. In many instances there can be significant potential for preventing disease morbidity and mortality if the disease is identified in the pre-symptomatic period.
If you would like to learn more about breast cancer, continue reading this related blog post: “Where to get Genetic Testing for Breast Cancer in Canada?”.
By MesserWoland [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC-BY-SA-2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)], via Wikimedia Commons