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DURHAM, N.C. -- Prostate tumors grew more quickly in mice
who exercised than in those who did not, leading to speculation
that exercise may increase blood flow to tumors, according to a
new study by researchers in the Duke Comprehensive Cancer
Center (DCCC) and the Duke Prostate Center.

"Our study showed that exercise led to significantly greater
tumor growth than a more sedentary lifestyle did, in this mouse
model," said Lee Jones, Ph.D., a researcher in the DCCC and
senior investigator on this study. "Our thought is that we may,
in the future, be able to use this finding to design better
drug delivery models to more effectively treat prostate cancer
patients, and those with other types of cancer as well."

The findings were presented in a poster session at the
American Association for Cancer Research annual meeting on
April 13 in San Diego, Calif. The study was funded by the
United States Department of Defense, the Prostate Cancer
Foundation and the American Urological Association Foundation,
Rising Star in Urology Award, given to Stephen Freedland, one
of the study's investigators.

The researchers implanted prostate tumors subcutaneously in
the flanks of 50 mice and then put half of the mice in cages
with exercise wheels and half in cages with no wheels. All mice
were fed the same diet. On average, the exercising mice ran
more than half a mile each day.

"We found that among the mice that had the opportunity to
voluntarily exercise, tumors grew approximately twice as fast
as they did among the mice that did not have the opportunity to
exercise," Jones said.

Researchers and clinicians know that a challenge in
delivering chemotherapy and radiation to tumors can be their
poor blood flow, so these findings may hint at a way in which
to improve blood flow to tumors, perhaps then allowing for
better distribution of medicine, he said.

"We're wondering, can we combine exercise with treatments
such as chemotherapy, hormone therapy or radiation, to maximize
the results we achieve in prostate cancer patients," Jones
said. "That question will be the subject of subsequent
studies."

The researchers are currently conducting a validation study,
in mice, in which tumors are injected directly into the
prostate, thereby better simulating human prostate cancer,
Jones said.

"Down the line, we will test this hypothesis in humans
undergoing medical treatment for prostate cancer," he said.

The researchers want to caution men against interpreting
these findings as an endorsement for not exercising for fear of
getting or exacerbating cancer.

"These mice were not receiving treatment and we were
allowing aggressive tumors to grow unchecked for the sake of
the experiment," said study investigator Freedland, a urologist
at Duke. "Patients would not find themselves in the same
situation."

Concerns should also be overridden by the well-established
benefits of exercise, including its positive effects on
cardiovascular health, Type II diabetes, obesity, and many
other chronic conditions, he said.

"This study gives us insight into which cellular pathways
are affected by exercise, and starts to give us clues about how
to harness the beneficial effects," said Michael Potter, a
medical student at Duke and lead investigator on the study.
"Ultimately, we hope that this knowledge will help us use
exercise to both deliver medicines more effectively and protect
the body from the harmful side effects of treatment, as we
already know it can."

This is one of the first studies to look at the
physiological effects of exercise on the tumor itself, rather
than examining the quality-of-life or symptom-control effects
of exercise in cancer patients, Jones said.

"The findings were a bit surprising, but provide a very
important and exciting foundation upon which to build," he
said.

Other researchers involved in this study include Susan
Poulton and Mark Dewhirst.