A NEW therapy that involves freeing up and boosting the immune system can wipe out advanced prostate cancer, early research has shown.

In mice, human disease tumours were "almost completely destroyed" by the animals' own immune systems, scientists said.

The treatment, dubbed "chemoimmunotherapy", involved low doses of the drug oxaliplatin which has a unique ability to activate cancer-killing immune cells.

But equally important to the treatment was removing or blocking immune system cells that put a brake on the body's defences.

The immunosuppressive "B-cells" are especially abundant in the tumours of men with advanced and spreading prostate cancer.

Under normal circumstances, the cells keep the immune system at bay, rendering conventional therapies ineffective and allowing tumours to grow unchecked.

US lead scientist Dr Shabnam Shalapour, from the University of California at San Diego, said: "The presence of such B-cells in human prostate cancer calls for clinical testing of this novel therapeutic approach."

Because of immunosuppression, advanced and aggressive prostate cancer does not typically respond to chemotherapy, researchers said.

B-cells also undermine the effectiveness of promising new drugs called checkpoint inhibitors which "unmask" cancer cells allowing them to be recognised by the immune system.

Each year in the UK around 41,000 men are diagnosed with prostate cancer and 11,000 die from the disease.

While early treatment is often highly successful, there are few options for men with aggressive drug-resistant prostate cancer that has started to spread.

B-cells play a number of vital immune system roles, including the production of antibodies.

Sometimes they also signal the immune system to slow down when it is getting overheated.

In the context of cancer, this can have undesirable consequences, researchers writing in the journal Nature said.

Co-author Professor Michael Karin, also from the University of California at San Diego, said there may be implications for the treatment of other types of cancer.

He said: "Similar immunosuppressive B-cells can be detected in other human cancers.

"This indicates that B-cell-mediated immunosuppression might be the reason several other cancers are also unresponsive to checkpoint inhibitors, raising the hope that chemoimmunotherapy will have broader applications for many cancer types."