Clues on Vitamin E's Anti-Prostate Cancer Effects

NEW YORK (Reuters Health) - Vitamin E appears to protect against prostate cancer and new research shows it may do so by interfering with two proteins that are associated with the disease.
Researchers based at the University of Rochester in New York found that adding vitamin E to prostate cancer cells inhibits the production of a receptor for testosterone, called the androgen receptor (AR), which is needed in order for the cancer to grow and develop.

"The fewer ARs there are in a (prostate cancer) cell, the less capable the remaining ARs, no matter how they are activated, are to turn on the genes that stimulate (prostate cancer) growth and progression," study author Dr. Edward M. Messing told Reuters Health.

"Thus, this can be combined with other AR inhibiting strategies to eliminate AR activity in (prostate cancer) cells," he added. In the US, prostate cancer is the second-leading cause of death among. Previous research has shown that vitamin E can protect against the development of prostate cancer, reducing risk from 18% to 12% among male smokers. However, researchers remained puzzled about how vitamin E, and not other antioxidants, lowered the risk of prostate cancer.

Now, the authors of the current study, led by Dr. Shuyuan Yeh, report that vitamin E inhibits the expression in prostate cancer cells of prostate-specific antigen (PSA), a protein that is often elevated in the disease and used as a marker for early detection.

The investigators also note in the May 28th issue of the Proceedings of the National Academy of Sciences that the vitamin can prevent cells from making androgen receptors.
In an interview with Reuters Health, Messing said he suspects the benefits of vitamin E stem from its interference with AR production. "The only thing we know of in 2002 that turns on PSA is an activated AR," he said.

Moreover, the researcher added, stopping the production of AR will halt the expression of all other genes that are activated by AR, which can also influence the development of prostate cancer. "While PSA serves as a good marker molecule of AR activity, more importantly the genes responsible for (prostate cancer's) growth, invasion and metastases, many of which depend upon an activated AR to turn them on, will be down-regulated or totally silenced as well," he noted.
All of the currently available treatments that aim to inhibit AR in prostate cancer cells primarily focus on preventing testosterone from binding to the receptor, Messing explained, but do not have long-term benefits, and can produce serious side effects in other parts of the body.
This is the first study to show how an agent can, in fact, specifically inhibit a prostate cancer cell's ability to manufacture AR, Messing added, and the vitamin appears to affect mostly prostate cancer cells.

Vitamin E might work best when administered with other natural treatments that also appear to protect against prostate cancer, such as vitamin D and selenium, the authors write.
In addition, combining vitamin E with an anti-androgen cancer drug called hydroxyflutamide prevented growth of prostate cancer cells better than either treatment did alone.

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