- Researchers analyzed genetic data to identify new genes linked to breast cancer.
- They found several new genes that may be linked to the condition.
- Further research is needed to know how variants on these genes affect breast cancer risk.
Breast cancer is the most common cancer globally, accounting for around 12.5% of new cancer cases worldwide. Genetic testing can be used to assess risk for the condition. Current tests consider risk variants on a small number of genes, including BRCA1, BRCA2, and PALB2.
However, known variants explain less than half of the familial relative risk of breast cancer, which is the probability of developing a condition if a family member has had it before. How much rare coding variants in other genes account for breast cancer risk remains largely unknown.
Understanding more about different breast cancer genes could improve the accuracy of genetic testing for predicting breast cancer risk.
Recently, researchers analyzed genetic data from 244,041 women to identify new gene variants linked to breast cancer. They found evidence for several new breast cancer risk genes and potential evidence for others.
The study was published in Nature Genetics.
“The study helps to identify additional genes that could be inherited and increase risk or explain family history of breast cancer. This becomes the launching pad for the next generation of data to help explain for the nearly 50% of individuals with family history that is not currently explained with genetics that we have available.”
— Dr. Louise Morrell, medical director of Lynn Cancer Institute, part of Baptist Health at Boca Raton Regional Hospital, who was not involved in the study, speaking to Medical News Today.
40 genes linked to breast cancer
For the study, the researchers analyzed genetic data from 26,368 women with breast cancer and 217,673 without. The women were primarily of European ancestry, although the researchers included some data from Malaysia and Singapore as well.
After analyzing the data, they identified 30 genes linked to breast cancer, of which six were particularly significant. These included five known susceptibility genes as well as one new gene: MAP3K1.
When the researchers restricted their analysis to patients ages 50 years and younger, they identified 40 genes linked to breast cancer.
“Although most of the variants identified in these new genes are rare, the risks can be significant for women who carry them. For example, alterations in one of the new genes, MAP3K1, appear to give rise to a particularly high risk of breast cancer,” said Dr. Jacques Simard, Ph.D., professor of medicine at Québec-Université Laval Research Center, in a press release.
Breast cancer risk in ‘European’ populations
MNT asked Dr. Jessica Jones, assistant professor of oncology with McGovern Medical School at UTHealth Houston, who was not involved in the study, about its limitations.
She indicated that as the study predominantly included women from Europe, the findings may not apply to more diverse populations.
“For example, the article overlooks some important genes, such as STK11 and TP53, because of how rare they are in Europe. They are not so rare here in the United States. These carry very high risks of cancer,” she noted.
She added that the study did not take into account how lifestyle factors such as obesity or alcohol consumption may impact breast cancer risk or the expression of genes.
MNT also spoke with Dr. Ora Karp Gordon, regional director of clinical genetics and genomics for Providence Southern California and Professor of Genetics at Saint John’s Cancer Institute in Santa Monica, California, who was also not involved in the study, about its limitations.
“The one significant new breast cancer susceptibility gene MAP3K1 is estimated to explain 0.14% of breast cancer risk, and all other genes combined [accounted for less than 1% of increased risk]. Thus, whether this approach can really lead to meaningful advancement from both a cost and data standpoint is a big unknown, [and perhaps unlikely],” said Dr. Gordon.
She added that the study only investigated coding regions of the genome and not other areas.
Genetic testing for breast cancer
“Despite more than ten years of utilizing next-generation sequencing techniques to investigate breast cancer susceptibility genes, more than 30% of the familial risk for breast cancer is still unidentified,” said Dr. Gordon.
She noted that this means current genetic testing cannot account for many cases of breast cancer.
“The majority of the missing ‘heritability’ of breast cancer risk may be in the non-coding genome and therefore only discoverable with whole genome sequencing, which remains cost-prohibitive at scale,” she added.
Dr. Jones noted that there is still a lot to learn about genes and that until they are ‘perfectly’ understood, genetic testing will not be offered to the entire population.
“A woman’s family history trumps this article. Regardless of whether we know a woman’s DNA make-up, if she has a strong family history [of breast cancer], she probably qualifies for enhanced breast cancer screening. If a woman reading this article wonders if her family has a genetic defect, science may need time to catch up with every gene—but she doesn’t have to wait to get more enhanced breast cancer screening.”
— Dr. Jones
Will these genes be tested in screening?
“Confirming this approach [with other demographics and datasets could significantly improve breast cancer risk assessments] for the many women who have a personal or family history [of the condition] but have had negative genetic testing results,” said Dr. Gordon.
Meanwhile, Dr. Jones said, “The study sheds new light on breast cancer risk related to ATRIP, MAP3K1, and SAMHD1 genes.”
“If a woman with breast cancer undergoes genetic testing and has [the risk variant], we can offer testing to her family to see if any children have also inherited [it]. If a child has inherited [a risk variant], we can change how we screen for breast cancer to include enhanced screening with breast MRI imaging,” she concluded.
Source: Read Full Article