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A new type of drug could benefit men with aggressive prostate cancer that is no longer responding to treatment, researchers from the Institute of Cancer Research have said.

In a study on mice, Hsp90 inhibitors were found to strip cancer cells of defences against hormone treatments.

This makes the drugs particularly promising for treating drug-resistant cancers, the research team said.

Prostate cancer is the most common cancer in men in the UK.

About one in eight men will get prostate cancer at some point in their lives. It mainly affects men over the age of 50.

The cancer can sometimes be treated successfully with hormone treatments, which target androgen receptors linked to the growth of male hormones called androgens.

But some prostate cancers don't work that way. Instead they create an abnormal form of androgen receptor which is not linked to the growth of hormones and therefore does not respond to standard hormone treatment.

This is the most common form of resistance in prostate cancer which leads to aggressive, difficult-to-treat cancers.

The latest research, published in the journal Cancer Research, found that a new class of drugs reduced production of both receptors.

Professor Paul Workman, study author and chief executive of the Institute of Cancer Research, said it was an exciting discovery.

"We call Hsp90 inhibitors 'network drugs' because they tackle several of the signals that are hijacked in cancer all at once, across a network rather than just a single signalling pathway.

"These drugs can hit cancer harder than those targeting only one protein, and look promising for preventing or overcoming drug resistance."

Prof Workman said the next step was to test the Hsp90 inhibitors in clinical trials on patients with aggressive, drug-resistant prostate cancer.

Prof Johann de Bono, a professor of experimental cancer medicine at the Institute of Cancer Research, said: "These drugs are already in clinical trials for several types of cancer, and I am excited that our work suggests they could also benefit men with prostate cancer who have otherwise run out of treatment options."