Anti-flu gene is linked to breast cancer

A GENE which fights flu is also linked to breast cancer, scientists revealed today.

The natural "defence" gene is vital for making antibodies to combat infections including the common cold.

But a study has shown how it turns deadly when activated by the hormone oestrogen. Experts said the discovery will enable scientists to develop new ways of treating and even preventing cancers in women.

The study was carried out by Cancer Research UK's London Research Institute and published in the Journal of Experimental Medicine.

More than 30,000 cases of breast cancer a year are blamed on high oestrogen levels. But scientists were baffled as to how the hormone triggered breast as well as ovarian cancer.

All women produce the chemical and the majority will not develop a hormone-related cancer. The body's defence gene - known as AID - also does not do any harm on its own.

But researchers found that when the two combine the body produces abnormal levels of chemicals which lead to cancer. These findings also raise concerns about treatments designed to increase levels of oestrogen, such as Hormone Replacement Therapy.