Now Viagra 'helps the body fight cancer'

VIAGRA and other impotence drugs help switch on the immune system to attack a range of cancers, a study has found.

The disease usually manages to avoid destruction partly because tumours produce a fog of chemicals that hide it from white blood cells.

But Viagra, a brand name for sildenafil, and other such drugs were found to reduce the amount of these chemicals, enabling the immune system to target the cancer more effectively.

Tests at the Johns Hopkins Kimmel Cancer Centre in the United States found the drug reduced the size of colon and breast tumours in mice threefold.

In mice which were genetically engineered to lack an immune system, the tumours were unaffected, showing that Viagra was helping the body's natural defence mechanisms fight the disease.

Laboratory tests on human cancer cells showed similar results and clinical trials are planned for next year.

They will also see if prostate cancer patients who take Viagra to deal with the impotence that can be a side-effect experience lower rates of recurrence.

Professor Ivan Borrello, of Johns Hopkins, said the drug might help prevent recurrence of the disease after surgery.

"I could envisage using it in combination with chemotherapy," he said.

Asked about human trials, Prof Borrello said: "You could go out tomorrow and buy the Viagra and give it to yourself; there's no reason why somebody couldn't starting doing it tomorrow if they wanted to. But it's expensive if you start taking it every day and you don't know how effective it is going to be.

"There are people who have had prostate cancer and developed impotence who are already doing it."

He said the technique should work for "solid" cancers but might also be effective against liquid ones such as leukaemia.

The study, reported in the Journal of Experimental Medicine, was the latest to show other uses for sildenafil beyond the most common one.

It was developed as a drug to treat hypertension by dilating blood vessels and lowering blood pressure.

Subsequent research suggested it could reduce the thickness of the heart wall and have other benefits relating to cancer.

Viagra suppresses levels of nitric oxide, one component of the fog which protects tumours from the immune system, and this is a critical compound involved in a variety of "signalling pathways" used in the body.