Genome detectives discover four more breast cancer genes

An international team of scientists say they have identified another four genes that increase a woman's likelihood of developing breast cancer.

The researchers say more than 60 percent of the women in the United States probably carry at least one of the mutations in one of the genes, called FGFR2.

The international team of experts led by scientists in the UK say the research represents the world's first large-scale "whole genome search" for breast cancer genes which entailed them sifting through the DNA of nearly 50,000 women.

Half of the women involved in the research were breast cancer patients, the other half were healthy and the team are optimistic that their discovery will lead to more genes being identified, and better tests developed to identify women most at risk.

The scrutiny of the genetic material revealed five suspect DNA regions hosting the four new genes, FGFR2, TNRC9, MAP3K1 and LSP1.

The team say the search methods are clearly effective and they feel many more breast cancer genes may now be found as well as genes for other cancers, including prostate, bowel and lung cancer; this would help prevent the disease because people who were at "particularly high risk of the disease" could be identified.

Experts say inherited cases make up between 5 and 10% of all breast cancer cases and lifestyle factors such as smoking and environmental issues are believed to account for the rest.

FGFR2 may be a logical candidate for a breast cancer gene -- it is a receptor, a kind of molecular doorway, for a compound called tyrosine kinase which is involved in several cancers.

It appears the new genes are far more common in the population than the well-known BRCA1 and BRAC2 genes, but carry a lower risk than the 50% to 85% risk for women with BRCA1 or BRCA2 developing breast cancer in their lifetime.

The new genes are thought to carry a 14% increased risk of developing breast cancer.

As the risk is relatively small, genetic testing for the four new genes is say the researchers unsuitable but as as more "low risk" genes are found, it may be possible to design tests for a combination of genes.

Currently, doctors only carry out tests for the BRCA1, BRCA2, TP53 and PTEN genes, but they believe there are hundreds more breast cancer genes to be found.

Lead author Professor Bruce Ponder, Director of Cancer Research UK's Cambridge Research Institute at the University of Cambridge, says at present how the genes interact with each other or with lifestyle factors is unclear.

The genome analysis technique which was used by the researchers allowed them to study all the significant pieces of DNA code they wanted in just a few hours.

According to the World Health Organization, breast cancer kills 500,000 people a year globally and 1.2 million men and women are diagnosed with it every year.

The research is published in the journal Nature Genetics.