Vitamin E Makes Prostate Cancer Cells Vulnerable
NY, 28 May 2002
E, a compound suspected of playing a role in preventing prostate
cancer, interferes with two proteins that play a central role in
the development of the disease, say scientists at the University
of Rochester Medical Center who report their findings in the May
28 issue of the Proceedings of the National Academy of Sciences.
led by Shuyuan Yeh, PhD, assistant professor in the departments
of Urology and Pathology, found that vitamin E interferes with the
ability of prostate cancer cells to make both prostate-specific
antigen (PSA) and the androgen receptor, a key player in the development
and progression of the disease. The work shows that the cancer cells
are vulnerable in a way previously unknown.
showed that in prostate cancer cells exposed to vitamin E, the PSA
level drops significantly, as much as 80 to 90 percent, a sign of
slowed cancer cell growth. Researchers also saw a 25 to 50 percent
decrease in the number of cancer cells, and under certain conditions
the compound killed off 90 percent of cancer cells.
the research was done in the laboratory and not in humans, it takes
on added significance because studies in people have already shown
that the compound may help prevent prostate cancer. In a study of
29,000 men in Finland, for instance, men who took the vitamin had
about one-third fewer cases of prostate cancer than men who did
not. But just how the compound might play a protective role has
been unclear, making it difficult to study or develop new treatments
that might mimic the vitamin's effect.
vitamin E is a known anti-oxidant that destroys harmful molecules
known as free radicals, some scientists have hypothesized that its
anti-oxidant properties might help prevent prostate cancer.
Yeh's team found that Vitamin E plays an unexpected role in prostate
cells. The compound has a dramatic effect on the androgen receptor,
a protein in the body that is vital to the growth of prostate cells,
including its cancer cells. Researchers found that vitamin E blocks
the assembly of the protein, exposing a new vulnerability in a protein
that is central to the development of the disease.
finding gives scientists a new lead to follow when targeting prostate
cancer. Currently many of the drugs used to treat prostate cancer
either stop the production of testosterone or are "anti-androgens"
that prevent testosterone from binding to the androgen receptor,
thus stopping the receptor from contributing to cell growth and
health. The new research suggests a way to disable the receptor
itself. It's a bit like finding a new way to cut off an engine's
fuel supply: One could stop the flow of gasoline, or one could simply
remove or disable the fuel tank.
someday instead of cutting off a man's testosterone supply to prevent
the androgen receptor from supporting prostate cancer cells, as
they do now, doctors will disable the androgen receptor itself,
much like vitamin E does. Or they might combine the approaches.
The team found that one traditional anti-androgen drug, hydroxyflutamide,
had little effect on the human metastatic prostate cancer cells
tested in their study. But when vitamin E was added to the mix,
cancer cell growth slowed dramatically.
is exciting and quite promising, but until we do further studies
in people, we can't really recommend that every man take vitamin
E to prevent the disease," says Edward Messing, a co-author and
professor and chair of the Department of Urology. Other authors
on the paper include graduate students Yu Zhang and Jing Ni; high
school student Eugene Chang of Pittsford Sutherland High School;
and Chin-Rang Yang, PhD, of the Department of Radiation Oncology.
scientists also caution that different forms of vitamin E produce
different results. The team found that a type known as vitamin E
succinate, also known as alpha-tocopheryl succinate, was most effective
in halting prostate cancer cells in the laboratory.
are several different kinds of vitamin E, and they have different
effects. Which type you're talking about makes a very big difference,"
says Yeh, whose research project was funded by the National Institutes
of Health and the Department of Urology. Yeh has worked closely
with Rochester scientist Chawnshang Chang, who discovered the androgen
the future, Yeh and Messing hope to study the effects of the vitamin
in patients with prostate cancer. The team will also continue to
study why some forms of the compound are more effective than others
in killing cancer cells. Finally, Yeh is studying vitamin D, another
compound that has been bandied about for its alleged role in preventing
prostate cancer. Yeh's team has found that vitamins D and E may
somehow work in concert, with vitamin E helping to boost the effectiveness
of vitamin D in killing cancer cells.
is also heading the local portion of a separate study designed to
test whether either vitamin E or selenium, or a combination, prevents
the disease. The SELECT trial (Selenium and Vitamin E Cancer Prevention
Trial) is the largest clinical trial yet of prostate cancer, a disease
which strikes about the same number of men -- approximately 200,000
-- as the number of women in the United States who get breast cancer.
Prostate cancer is the second-leading cause of death from cancer