Racemase and Diet
But using racemase as a marker for cancer is just the proverbial tip of the iceberg, say De Marzo and Isaacs.

Racemase itself is not a “new” gene; scientists have known for years that it plays a key role in the body’s metabolism of fatty acids. It makes an enzyme that “takes branch-chain fatty acids, which are found in dairy products and red meat, and converts them to a form that we can burn as energy,” says De Marzo. But the fatty acids in question are very specific, adds Isaacs. “You don’t need this enzyme for most fatty acids. However, you do need it to metabolize a type of fatty acid that’s particularly prominent in dairy products.” This acid, called phytanic acid, comes from phytol, which in turn is derived from chlorophyll. Which means, Isaacs explains, “that animals that eat a lot of grass end up incorporating a lot of phytanic acid into their milk and meat.” Think cows, and think—as De Marzo and Isaacs are thinking, with growing excitement—of the known links between red meat and dairy products and prostate cancer.

Scientists have known for several years that men who consume large amounts of dairy products or red meat are more likely to develop metastatic prostate cancer, and to die of the disease.

“This may be the best scientific evidence to support the concept that dietary factors influence the growth of prostate cancer.”

What De Marzo, Isaacs, and colleagues are learning about racemase may help explain why. Racemase is expressed nine times higher in prostate cancer than in normal tissue. This means that when men with prostate cancer eat red meat or dairy products, the cancer cells have the potential to gain and use more energy from these foods than normal cells can. And something else happens, too: When the body metabolizes phytanic acid, it makes a toxic byproduct—hydrogen peroxide. “Right now it’s complete speculation, but this may turn out to increase oxidative stress in the cell,” says Isaacs. Oxidative damage is incremental harm, caused over many years, as free radicals—a harmful result of everyday metabolism— attack the DNA in cells, causing mutations that lead to cancer, or cause it to progress.

For years, there has been increasing scientific speculation on the role diet may play in preventing progression of prostate cancer. Says Urologist-in-chief Patrick C. Walsh, M.D.: “This may be the best scientific evidence to support the concept that dietary factors influence the growth of prostate cancer. I am impressed enough by these data to use them in making recommendations to patients. I tell men who are considering watchful waiting, or who have PSA progression after surgery or radiation therapy that they should markedly limit their intake of red meat and dairy products.” (Fat-free milk is fine, Walsh adds.)

And the microarrays launched it all. “Here’s a gene that we never would have thought about ordinarily,” says Isaacs. “We were not even aware of this pathway, or phytanic acid, or what any of these things were, and here’s this gene that comes screaming up on our arrays. This not only gives us a new marker for prostate cancer —it may give us some insight into the mechanisms by which normal prostate cells convert to cancer cells. And perhaps it could prove this idea that reducing dairy products in the diet may be an important way to prevent or slow the progression of prostate cancer.”