A drug used to treat obesity has some benefits for a completely different disease -- cancer.

Five years ago, scientists at Wake Forest University School of Medicine were surprised to find the drug orlistat (Xenical or Alli ) could kill cancer cells. Now, they report on how it works. The drug binds and interacts with a protein found in tumor cells, blocking its function and causing the cells to die.

The protein is known as fatty acid synthase. It is found in many tumor cells including those of the prostate, breast, colon, ovaries, liver, lung, and brain.

"High levels of fatty acid synthase correlate with a poor prognosis, so it is a great treatment target," assistant professor Steven Kridel, Ph.D., of Wake Forest University School of Medicine, was quoted as saying. "This makes an exciting treatment target because, theoretically, you don't have to worry about harming nearby healthy tissue."

Researchers say orlistat alone cannot treat cancer because while the drug can kill cancer cells in the lab, it is designed to act only in the digestive tract in humans. Now, the goal is to develop a drug like orlistat that can go through the bloodstream to the site of the tumor.

Wake Forest scientists have screened hundreds of thousands of compounds to find the ones that interact with cancer cells like orlistat does. They have narrowed down the list to a dozen and will now work to optimize the compounds to determine if they can create a potent cancer treatment.

Fatty acid synthase is also found in fat cells. This suggests if scientists successfully develop a drug to treat cancer, it could also be used to treat obesity.

SOURCE: Nature Structural and Molecular Biology, published online July 8, 2007