A multi-centre international team of researchers has uncovered a new gene that may raise a woman's likelihood of contracting breast cancer by more than a third.
The researchers have also found that the gene called HMMR interacts with the well-known breast cancer gene BRCA1, and that alterations in either gene cause genetic instability and interfere with cell division, which could be a path to breast cancer developing.
According to the researchers, they have not only discovered a single gene that is linked to breast cancer, but also a pathway that may be a potential target for diagnosing or treating the disease.
They have also revealed that HMMR is mutated in about 10 per cent of the population, while mutations in the two main genes involved in breast cancer susceptibility—BRCA1 and BRCA2—occurs in less than one per cent of the population.
"If we can identify variations of genes that are more common in the population that increase breast cancer risk, then targeting that gene for early detection or treatment will have a greater impact," Nature magazine quoted Kristen Stevens, a doctoral student in epidemiology at the University of Michigan School of Public Health and one of the lead authors on the paper, as saying.
At the outset, the researchers developed a computerised network-modelling tool that enabled them to analyse many different types of existing scientific data sources, whereby they could identify genes that impact cancer development.
The analysis was first focussed on four genes known to play a role in breast cancer, namely, BRCA1, BRCA2, ATM and CHEK2. It helped researchers to determine how each of the genes interacted with other genes in the body.
The researchers said that their analysis depicted HMMR as a key player in breast cancer.
"These findings made us wonder whether HMMR might also be a breast cancer susceptibility gene," says study author Dr. Stephen Gruber, the H. Marvin Pollard Professor of Internal Medicine at the U-M Medical School.
With a view to determining whether variations in HMMR could heighten breast cancer risk, the researchers studied the genes of 923 Jewish Israeli women with breast cancer, and similar women without breast cancer in a research led by Dr. Gadi Rennert, director of the CHS National Cancer Control Center in Haifa, Israel.
The selection of the Ashkenazi Jewish population in Israel for the study was down to the fact that it carries a higher risk of breast cancer than other ethnicities.
It was found that women with a variation in the HMMR gene had a higher risk of breast cancer, even after accounting for mutations in the BRCA1 or BRCA2 genes.
The researchers said that the risk of breast cancer in women under age 40, who carried the HMMR variation, was 2.7 times the risk of women without the variation.
The researchers verified their findings in a second group of Ashkenazi Jewish women in New York who had a family history of breast cancer but no identified BRCA1 or BRCA2 mutations, and in a third study of Jewish women with and without breast cancer in New York.
It was found that the risk of breast cancer was 23 per cent higher in women who had one copy of genetic variant, and 46 per cent higher in women who had inherited two copies.
Since the subjects in the two studies were 12 months younger than women from the control group, the researchers suggest that HMMR is linked to early-onset breast cancer.
"Identifying genes involved in cancer in the general population is important, because not all of the causes of breast cancer have been found. Through discoveries such as this, someday we might be able to more precisely estimate a person's risk of cancer based on their genes," says study author Dr. Laura Rozek, a postdoctoral research fellow at the U-M Medical School.