Four new genes that increase the risk of breast cancer have been discovered. The disease, pictured here at the cellular level, is the most common form of cancer in women.

Credit: Wikimedia

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SYDNEY: Four new genes that increase the risk of breast cancer have been identified, and scientists believe they hold the key to uncovering all others behind the deadly disease.

The finding represents "the light at the end of the tunnel" according to Georgia Chevenix-Trench of the Queensland Institute of Medical Reasearch in Brisbane, who was involved in the international study. She said researchers now understand how to find the other genes involved.

"When we've got more [genes] – maybe 20, 50 or 100 – we'd be able to screen a large proportion of the population relatively cheaply and identify the 10 per cent at highest risk, and channel them into better screening," Chevenix-Trench told The Sydney Morning Herald.

Culprits common

Until now, only about 25 per cent of the genes that are suspected to cause inherited breast cancer have been identified. These new culprits – flawed versions of genes called FGFR2, TNRC9, MAP3K1 and LSP1 – are believed to account for an additional four per cent.

British-led researchers found the new genes after sifting through through the DNA of nearly 50,000 women, half of them healthy and half of them patients with breast cancer. Telltale "tags" of DNA code among the breast cancer group highlighted the four genes.

According to the reaserchers, who published their findings today in the British journal Nature, flawed versions of the four genes are common in the general population. The good news, though, is that the genes are considered relatively low hazard, meaning that women who have them run a comparatively small risk of developing cancer.

By contrast, the notorious breast cancer genes BRCA1 and BRCA2 are relatively rare in the population, but women who have them run a high risk of developing the disease.

Better diagnostics

Diagnostic tests for BRCA1 and BRCA2 are helping to save many lives, as women at risk are alerted and encouraged to have regular breast scans.

But according to Cancer Research U.K., whose scientists led the massive investigation, individual tests for the four new genes may be unsuitable, since they are so common yet relatively low-risk.

However, "as more of these 'low-risk' genes are found it may be possible to design tests for a combination of genes," the researchers said. "This could help doctors make decisions about prevention, diagnosis and treatment for women who inherit faults in one or more of these genes."

Much remains to be learnt about the four genes, especially whether they react with each other or with lifestyle factors in a way that boosts the risk for some women.

Breast cancer is the most common form of cancer affecting women, the World Health Organisation said in February 2006. Genetic causes account for between five and 10 per cent of cases, with "lifestyle factors" such as smoking and environmental factors accounting for the rest.

In 2005, breast cancer caused 502,000 deaths, accounting for seven per cent of all cancer mortalities and almost one per cent of all deaths worldwide.