SCIENTISTS have made a discovery which they hope will lead to new treatments for the progressive wasting which causes the deaths of thousands of cancer patients.

A new study suggests proliferating cancer cells actively cause the body to starve by simulating an effect of diabetes.

The research, conducted on fruit flies, points towards potential new treatments for cachexia - the wasting that accompanies advanced cancers.

Around a fifth of cancer deaths are due to cachexia, which can render patients too weak to withstand chemotherapy and radiotherapy and increase their susceptibility to side effects.

Typically raising food intake does little to stem the loss of muscle and fat.

Scientists in the US now believe tumour cells actively secrete proteins that inhibit insulin, the hormone responsible for energy-giving glucose being absorbed into the body tissues.

In this way more of the sugar is made available to satisfy the cancer's enormous appetite for glucose.

People with diabetes either lack insulin or fail to respond to it, so that their tissues are also prevented from absorbing glucose.

Researcher Dr Young Kwon, from Harvard Medical School in the US, said: "The findings suggest that the proliferating tumour cells consume a lion's share of glucose for energy, while the rest of the body progressively starves."

Clues to the process emerged from two studies of cachexia in fruit flies with cancer. Tumours in the insects secreted a molecule called ImpL2 that triggered the loss of fat and muscle tissue, replicating cancer-induced wasting in humans.

ImpL2 is the fly version of mammalian insulin growth factor binding proteins (IGFBPs) which inhibit the activity of insulin in humans and other mammals.

Lowering ImpL2 levels in the flies significantly reduced wasting, suggesting that targeting its molecular twin in humans might provide a way of treating cachexia.

A key question is how growing tumours evade the effects of insulin-suppression, which might be expected to cut off their supplies of glucose as well.

The answer could be linked to differences in insulin signalling and glucose metabolism that shield the cancer from starvation, the research suggests.

Dr David Bilder, from the University of California at Berkeley, who led one of the studies published in Developmental Cell, said: "Many cancer patients die not because of the local effects of tumours, but rather from more broad, systemic changes to the entire body that are induced by these tumours.

"One of the worst of these long-range effects is wasting syndrome, also known as cachexia, which is a major obstacle to cancer treatment.

"The two new studies illustrate the power of using simple model organisms to provide new insights relevant to the most important questions of human cancer biology."

Depletion of ImpL2 did not fully reverse tissue loss in the flies, indicating that other unknown factors are also involved.