LONDON (Reuters) - Scientists in Britain have identified a genetic mutation involved in certain types of lung cancer and said the breast cancer drug Herceptin might work in patients who have it.

The gene called ERBB2 is linked to four percent of non-small-cell lung cancers (NSCLC), which account for about 75 percent of all cases of the deadly disease.

"ERBB2 is one of a series of biological switches in our cells that plays a vital role in controlling whether cells survive and proliferate," Dr. Andy Futreal, a co-leader of the Cancer Genome Project which found the gene, said on Wednesday.

"When the ERBB2 protein is switched on, it talks to other molecules in the cell to initiate a cascade of changes that alter how cells grow."

Some mutations in the gene result in uncontrolled cell division, or cancer.

ERBB2 also plays a role in some cases of breast cancer, which are treated with Herceptin (trastuzumab). The drug made by U.S. group Genentech Inc. and Switzerland's Roche Holding AG dampens the activity of ERBB2.

Herceptin was designed to treat cancers in patients whose tumours over-express the growth-promoting HER-2 gene. It is suitable for about a quarter of breast cancer patients.

"We have an existing drug that works against the overactive ERBB2 protein," Futreal, who reported the findings in the science journal Nature, said.

"And (we) can now identify patients with NSCLC who have mutations in this gene. Our understanding from other studies suggests that these patients may benefit from treatment with anti-ERBB2 agents," he added in a statement.

Lung cancer is the biggest cancer killer in men and second only to breast cancer in female deaths. Non-small-cell lung cancers are not usually diagnosed until the cancer has spread beyond the lung and does not respond well to existing forms of chemotherapy.

The ERBB2 mutation also occurs in 10 percent of adenocarcinoma, the most common form of lung cancer, which is found in smokers.

The Cancer Genome Project at the Wellcome Trust Sanger Institute in England is cataloguing changes within the genome of cancer cells. By identifying mutations that can lead to the development of cancer they hope to be able to search for new treatments and identify the best therapy for each patient.

"With this strategy of searching for the root of gene problems we have an opportunity to make progress in the treatment of other cancers. I have to stress, however, we are still a long, long way from cures," he added.

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