Their study, in the journal Cancer Research, is the latest
tantalizing suggestion of a possible role for vitamin D, from the
sun or diet, in reducing prostate cancer risk, the second leading
cancer killer of men. More than 40,000 men are expected to die
of the disease this year.
NIEHS' Jack A. Taylor, M.D., Ph.D., and colleagues found
that two alleles on the vitamin D receptor gene may affect the
risk of prostate cancer. An allele is a slight, naturally
occurring variation of a gene -- in this case, the gene which
helps control how vitamin D is utilized by the body's cells.
Two alleles are inherited, one from each parent. They come
in two forms designated by researchers as either T or t, so that
each person ends up with one of three combinations, TT, Tt, or
The study found that men inheriting the tt allele seem to
enjoy one-third less likelihood of developing prostate cancer
requiring surgery. Does the tt combination provide for better
use of vitamin D? "We can't say yet, but we'll be pursuing an
answer," Dr. Taylor said.
The alleles were studied in blood samples from 108 prostate
surgery patients, less than 10 percent had tt and most had TT or
Tt alleles, and from 170 male non-cancer patients at nearby hospitals
of the University of North Carolina, Chapel Hill, N.C.,
and Duke University, Durham, N.C. Well under 10 percent of the
prostate surgery patients had tt alleles, whereas about one in
five of the controls did.
This study follows one in which other investigators found
that men living in northern latitudes with less total sunlight
exposure (and therefore less production of vitamin D by the skin)
seem to have a higher incidence of prostate cancer.
Another study shows that vitamin D suppresses prostate
cancer cells cultured in the laboratory. And a rodent study has
suggested that vitamin D analogs may protect against prostate
Dr. Taylor said, "Together with these other studies, our
findings support the idea that vitamin D plays an important role
in prostate cancer, but it is too early to start applying these
results to human prevention strategies or therapies.
"We certainly are not ready to suggest using vitamin D in
prostate cancer prevention," Dr. Taylor said, "but we are very
excited about trying to move this line of research forward to
determine how the tt alleles may change the utilization of
NIEHS is one of the National Institutes of Health, most of
which are in Bethesda, Md., but NIEHS is located in central North
Carolina. Dr. Taylor is in the Epidemiology Branch of the
Environmental Diseases and Medicine Program at NIEHS.
In 1995, other NIEHS researchers, in collaboration with
scientists from Johns Hopkins University, identified and cloned a
gene that suppresses the spread of prostate cancer. Like many
other cancers, prostate cancer may result from interactions
between a genetic susceptibility and environmental factors, such
as smoking, diet and exposures to chemicals and radiation.