Gene mutation linked to early-onset breast cancer

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October 7, 2007 23:16

BRCA genes carried by Ashkenazi Jewish women are responsible for some 8% of their breast cancers.

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Gene mutation linked to early-onset breast cancer

cancer cell 88. (photo credit: )

An international study that included Israelis has identified a new breast cancer gene that may increase the risk of the tumor by more than a third. The gene, named HMMR, follows the discoveries years ago of the breast cancer gene mutations known as BRCA1, BRCA2, APTM and CHEK2. BRCA genes are carried by about 2.5 percent of Ashkenazi Jewish women and are responsible for about 8% of all breast cancers in this population. Ashkenazi Jews in Israel and abroad carry a higher risk of breast cancer than other ethnic groups. The researchers Spain, Israel and several centers in the US found the HMMR gene interacts with BRCA1. Alternations in either gene cause genetic instability and interfere with cell division, which could be a path to the development of breast cancer. The researchers said their discovery could lead to the finding of a "pathway" that may be a potential target for treating or detecting breast cancer. Results of the study appeared Sunday in the advance on-line edition of the prestigious journal Nature Genetics. Those women with the HMMR mutation were diagnosed an average of 12 months earlier than women from the control group, suggesting that the gene is linked to early-onset breast cancer. HMMR is mutated in about 10% of the population. Mutations in the two main genes involved in breast cancer susceptibility, BRCA1 and BRCA2, occur in about one of every 300 individuals, or less than 1% of the general population. Researchers started by developing a network modeling tool that allows many different types of existing scientific data sources to be analyzed easily to identify genes that impact cancer development. The researchers started with four genes already known to play a role in breast cancer - BRCA1, BRCA2, APTM and CHEK2. They were then able to see how each of these genes interacts with other genes. Through this model, HMMR emerged as a key player in breast cancer. The authors then showed that alterations of either BRCA1 or HMMR can lead to genetic instability and interfere with cell division. "These findings made us wonder whether HMMR might also be a breast cancer susceptibility gene," said the study's senior author, internal medicine Prof. Stephen Gruber of the University of Michigan Medical School. To understand whether variation in HMMR increases breast cancer risk, the researchers looked at the genes of 923 Israeli women with breast cancer and similar women without breast cancer examined in a human validation study led by Prof. Gad Rennert of the National Cancer Control Center at Carmel Medical Center and the Technion-Israel Institute of Technology's Rappaport Faculty of Medicine in Haifa. This component of the study found that women with a variation in the HMMR gene had a higher risk of breast cancer, even when accounting for mutations in the BRCA1 or BRCA2 genes. In particular, the risk of breast cancer in women under age 40 who carry the HMMR variation was 2.7 times the risk in women without this variation. In total, 2,475 women with breast cancer and 1,918 healthy women were studied in Israel and New York. Overall, the risk of breast cancer was 23% higher in women who had one copy of genetic variant, and 46% higher in women who had inherited two copies.


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