High Antioxidant Levels Lower Prostate Cancer Risk
March 15, 2004 - 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.
Contact: Russell Vanderboom, Ph.D.
vanderboom@aacr.org
215-440-9300
American Association for Cancer Research
