The study, published online in two papers in the Proceedings of the National Academy of Sciences, said hormone therapy, a common treatment for men with advanced prostate cancer, generally keeps the cancer at bay for a year or two. But then, for reasons scientists have never understood, the treatment fails in patients whose disease has spread.

Chawnshang Chang, director of the George Whipple Laboratory for Cancer Research at the University of Rochester Medical Center, said that the androgen receptor -- through which male hormones like testosterone work -- is much more versatile than previously believed.

Under certain conditions the molecule spurs growth, and at other times the molecule squelches growth, just like the same molecule does to hair in different locations on a man's head.

The findings raise the possibility that under some conditions, some treatments designed to treat prostate cancer could instead remove one of the body's natural brakes on the disease. However, the researchers stress the results are based on laboratory studies in mice and it's too soon to know whether the findings apply to men.