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A common fat found in corn oil appears to increase the growth of prostate cancer tumours, researchers report.
Omega-6 fatty acids appear to cause human prostate tumours to grow twice as fast as tumours not exposed to omega-6 fats, according to the researchers at the San Francisco Veterans Administration Medical Centre.

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One particular omega-6 fatty acid, arachidonic acid, turns on a gene that leads directly to tumour growth, the researchers found. Their report appears in the February 1 issue of Cancer Research.

"Some of the fat [that] people eat can actually trigger growth of tumours," said lead researcher Millie Hughes-Fulford, director of the Laboratory of Cell Growth.

Promotes tumour growth
Omega-6 doesn't cause cancer, Hughes-Fulford stressed. "It's more like a promoter for a latent tumour to be able to grow," she added.

In its study, Hughes-Fulford's team treated prostate cancer tumour cells in a laboratory with omega-6 fatty acid. They found these cells grew twice as fast as similar cells not exposed to omega-6.

In addition, the researchers found when they added a non-steroidal anti-inflammatory, or a PI3K inhibitor, such as what's found in painkillers, the gene did not get switched on and tumour cell growth did not occur.

Since the early 1960s, people have been consuming more and more corn oil, Hughes-Fulford noted. "Corn oil is very high in omega-6 fatty acid," she said. "We are eating about 25-fold more of this than we were eating at the turn of the century."

Corn oil linked to other cancers
Hughes-Fulford stressed this added consumption of corn oil is not increasing the risk of all cancers in all people. "But we have seen it in colorectal cancer, now we have seen it in prostate, and some people have seen the same type of thing in breast cancer," she said. "One has to ask the question: Why would one increase one's diet in something that could be associated with an increased incidence of tumour growth?"

Hughes-Fulford advises cutting down on the amount of omega-6 fatty acids in the diet. "What I have done, and all the people that know my work have done, is we have mainly switched over to olive oil and canola oil," she said.

"It's a matter of choices," Hughes-Fulford said. "For a healthy lifestyle, it's not a secret, omega-3 fatty acids are good and omega-6 acids are not as good. You need some omega-6, it's just that it's much better if we moderate our intake of omega-6 acids."

Fish and green vegetables are other good sources of omega-3 fatty acids, she said.

Consistent with other research
One prostate cancer expert said the new finding is consistent with research experiments his group has performed.

"A growing body of evidence suggests that omega-6 fatty acids may play an important role in the progression of prostate cancer," said Dr William Aronson, an associate clinical professor of urology at the University of California, Los Angeles.

"The backbone of the modern diet, corn oil, is a rich supply of linoleic acid - omega-6," Aronson said. "Linoleic acid is converted in the body to arachidonic acid. Our group has previously demonstrated that reducing dietary corn oil slowed the progression of human prostate cancers grown in mice."

Aronson believes the results of these studies will lead to ways to slow down the progression of prostate cancer. "By either reducing omega-6 fatty acid intake or possibly using targeted therapies that effect increased P13K signalling by arachidonic acid, hopefully, investigators will develop successful strategies for preventing the progression of prostate cancer," he said.

Expert questions conclusions
But another expert thinks the findings don't apply to prostate cancer.

"The model using the PC3 prostate cancer cells is irrelevant," said Ajit K. Verma, a professor of human oncology at the University of Wisconsin Medical School. "So, the implications of the findings to the treatment of prostate cancer are questionable."

"It is dangerous to conclude that reduction of omega-6 fatty acid intake and anti-PI3K inhibitors may be worth considering as future therapeutic approaches to battle prostate cancer," Verma said. - (HealthDayNews)

Visit our Prostate Centre for more information.

February 2006
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