| ironjustice@aol.com 2005-03-19, 5:36 pm |
| Public release date: 15-Mar-2005
Contact: Russell Vanderboom, Ph.D.
vanderboom@aacr.org
215-440-9300
American Association for Cancer Research
Antioxidant blood levels key to MnSOD gene
PHILADELPHIA - Greater levels of selenium, vitamin E and the tomato
nutrient lycopene have been shown to reduce prostate cancer in one out
of every four Caucasian males -- those who inherit a specific genetic
variation that's particularly sensitive to oxidative stress.
Conversely, if carriers of this genetic variant have low levels of
these vitamins and minerals, their risk of aggressive prostate
increases substantially, as great as 10-fold, over their cohorts who
maintain higher levels of these nutrients.
These results, published in the March 15 issue of the journal Cancer
Research, were based on the analysis of 567 men diagnosed with prostate
cancer between 1982 and 1995, and 764 cancer-free men from the
Physicians Health Study (PHS).
"This large prospective study provides further evidence that oxidative
stress may be one of the important mechanisms for prostate cancer
development and progression, and adequate intake of antioxidants, such
as selenium, lycopene and vitamin E, may help prevent prostate cancer,"
said Haojie Li, M.D., Ph.D., a researcher at the Brigham and Women's
Hospital and Harvard Medical School.
Destructive molecules known as "free radicals" have been shown to team
up with oxygen in the human body resulting in oxidative stress and what
some scientists believe is an assortment of age-related ailments. As a
result, many believe that consumption of antioxidants can slow that
process.
"Our study, as well as many other epidemiological studies, encourages
dietary intake of nutrients such as lycopene from tomato products, or
supplements for vitamin E and selenium to reduce risk of prostate
cancer," said Li.
The initial goal of the PHS study was to assess the effect of aspirin
and beta carotene on men's health. Since blood samples collected in
1982 were available from many of the study's participants, the research
team decided to review variants for the gene that codes for manganese
superoxide dismutatase (MnSOD), an important enzyme that works as an
antioxidant in human cells to defend against disease. The MnSOD gene is
passed from parents to offspring in one of three forms: VV, VA or AA.
"Compared with men with the MnSOD VV or VA genotype, people with the AA
genotype seem to be more sensitive to the antioxidant status," said Li.
"Men with the AA genotype are more susceptible to prostate cancer if
their antioxidant levels are low."
The study's results found that a quarter of the men in the study
carried the MnSOD AA genotype, half carried the VA genotype, and the
remaining quarter carried the VV genotype.
The results indicated that the VA and VV men were at equivalent risk
for developing prostate cancer across all levels of antioxidants in
their blood. Compared to MnSOD VV or VA carriers with low selenium -
those men in the lowest quartile of the study group - MnSOD AA males
had an 89 percent greater risk for developing aggressive prostate
cancer if blood levels for selenium were low.
On the other hand, MnSOD AA carriers with high selenium - those men
in the highest quartile - had a 65 percent lower risk than the MnSOD
VV or VA males who maintained low levels of selenium.
"The levels of selenium in the highest quartile of these men are not
abnormally high," Li said. "Our range is neither extremely high nor
extremely low."
While similar trends were observed for lycopene and vitamin E when
tested independently, the contrast in relative risk was most pronounced
for the men who had high blood levels for all three antioxidants
combined.
"Among men with the MnSOD AA genotype, we observed a 10-fold difference
in risk for aggressive prostate cancer, when comparing men with high
versus low levels of antioxidants combined," said Li. "In contrast,
among men with the VV or VA genotype, the prostate cancer risk was only
weakly altered by these antioxidant levels."
Similar interactions between dietary antioxidants and the variations in
the MnSOD gene have previously been linked to risk for breast cancer.
###
Founded in 1907, the American Association for Cancer Research is a
professional society of more than 24,000 laboratory, translational, and
clinical scientists engaged in all areas of cancer research in the
United States and in more than 60 other countries. AACR's mission is to
accelerate the prevention and cure of cancer through research,
education, communication, and advocacy. Its principal activities
include the publication of five major peer-reviewed scientific
journals: Cancer Research; Clinical Cancer Research; Molecular Cancer
Therapeutics; Molecular Cancer Research; and Cancer Epidemiology,
Biomarkers & Prevention. AACR's Annual Meeting attracts more than
15,000 participants who share new and significant discoveries in the
cancer field. Specialty meetings, held throughout the year, focus on
the latest developments in all areas of cancer research.
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