New breast cancer gene discovered

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New breast cancer gene discovered

By Mulvihill

NEW YORK, Apr 22 (Reuters Health) - An international team of researchers

reported on Monday that they have discovered a new breast cancer gene

that is believed to be associated with 1% of all female breast cancer

cases and 9% of all male breast cancer cases.

The mutation in the gene, known as CHEK2, confers a twofold increase in

breast cancer risk in women, who typically have about a 13% chance of

developing cancer in their lifetime. The gene mutation carries a tenfold

increase of a man's risk of breast cancer, a much rarer occurrence.

In contrast, the known breast cancer genes BRCA1 and BRCA2 are " riskier "

in terms of developing cancer. About 50% to 60% of women with those

genes develop cancer by age 70.

" We have suspected that 'low risk' cancer genes exist but they have been

difficult to prove with certainty, " said Dr. Nazneen Rahman of the

Institute of Cancer Research in Surrey, UK, in an interview with Reuters

Health. " (The CHEK2 discovery) is the first to be proved to a high

degree of certainty, " Rahman added.

In the investigation, the researchers found that the CHEK2 mutations

were found in 5.1% of 1,071 breast cancer patients without a mutation in

the BRCA1 or BRCA2 genes, according to the report published in the April

21st issue of the journal Nature Genetics.

However, only 1.1% of 1,620 healthy people were found to have the gene

variation.

The CHEK2 gene is located on human chromosome 22, according to Rahman,

and it plays a role in the repair of damaged DNA.

" DNA damage can cause cancer and thus if the function of CHEK2 in

repairing DNA is reduced then the likelihood of cancer can occur, "

Rahman told Reuters Health.

The researchers believe that CHEK2 acts in concert with another, as yet

unidentified gene, to cause breast cancer.

The new discovery adds to a small but growing body of research about the

role genes play in breast cancer.

Currently, experts know that a family history of breast cancer is one of

the strongest risk factors for breast cancer, especially among young

women. Nearly half of women with early-onset breast cancer have a family

history of breast or ovarian cancer, yet only 9% of these women have a

BRCA1 or BRCA2 mutation, suggesting that other genetic factors may play

a role.

Although early-onset breast cancer has a strong genetic link, scientists

report that they have yet to discover the genes responsible for the

disease in most patients.

With regard to the implications for breast cancer treatment and or

prevention, Rahman emphasized caution in interpreting the results.

" One percent of the population carries this mutation, but only a

minority will go on to develop breast cancer--therefore it is unclear at

this stage whether people with the mutation would benefit from any

different management. "

He added, " In the long-term, this finding informs us about the

biological pathways and genes that are involved in breast cancer and

this information is helpful in developing new treatments. "

SOURCE: Nature Genetics 2002;DOI:10.1038/ng879.