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A new study has pinpointed a molecular cause of cachexia, raising the prospect of more effective treatments. 

Cachexia is a wasting of fat and muscle occurring in about half of all cancer patients. It also increases their risk of death.

The study demonstrated that in mice bearing long tumors, their symptoms of cachexia improved or prevented in some cases, when given an antibody that blocked the effects of a protein, PTHrP, secreted by the tumor cells. PTHrP - parathyroid hormone-related protein - is known to be released from many types of cancer cells. 

Researchers added that the study is first to explain in detail how parathyroid hormone-related protein from tumors switches on a thermogenic process in fatty tissues, resulting in unhealthy weight loss. 

Researchers in their second experiment, observed that the antibody treatment prevented the loss of muscle mass and improved muscle function, while control animals developed severe muscle-wasting. 

"You would have expected, based on our first experiments in cell culture, that blocking PTHrP in the mice would reduce browning of the fat," said lead researcher Bruce Spiegelman, PhD, in the press release. "But we were surprised that it also affected the loss of muscle mass, and improved health."

Thus, the role of PTHrP "is definitely not the whole answer" to the riddle of cachexia, noted Spiegelman, but may be a necessary part, while other factors are also involved.

The study has been reported in the July 13 advanced online edition of Nature.