"Previous research has shown protection against prostate cancer, but this is one of the first studies to show protection against advanced prostate cancer and interaction with COX-2," said John S. Witte, Ph.D., professor of epidemiology and biostatistics at the University of California San Francisco.

For the current study, researchers performed a case-control analysis of 466 men diagnosed with aggressive prostate cancer and 478 healthy men. Diet was assessed by a food frequency questionnaire and researchers genotyped nine COX-2 single nucleotide polymorphisms.

Researchers divided omega-3 fatty acid intake into four groups based on quartiles of intake. Men who consumed the highest amount of long chain omega-3 fatty acids had a 63 percent reduced risk of aggressive prostate cancer compared to men with the lowest amount of long chain omega-3 fatty acids.

The researchers then assessed the effect of omega-3 fatty acid among men with the variant rs4647310 in COX-2, a known inflammatory gene. Men with low long chain omega-3 fatty acid intake and this variant had a more than five-fold increased risk of advanced prostate cancer. But men with high intake of omega-3 fatty acids had a substantially reduced risk, even if they carried the COX-2 variant.

"The COX-2 increased risk of disease was essentially reversed by increasing omega-3 fatty acid intake by a half a gram per day," said Witte. "If you want to think of the overall inverse association in terms of fish, where omega-3 fatty acids are commonly derived, the strongest effect was seen from eating dark fish such as salmon one or more times per week."

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The researchers looked at gene expression patterns in 166 ovarian cancer tissue samples taken from patients who were treated at Duke, H. Lee Moffitt Cancer Center and Memorial Sloan-Kettering Cancer Center and from the Gynecologic Oncology Group Tumor Bank. For this study, researchers examined samples of advanced ovarian cancers from patients who had experienced long-term survival -- over seven years -- and patients who had done extremely poorly, and died within three years of diagnosis.

The researchers used microarrays “ a method for examining thousands of snippets of DNA -- with about 22,000 probe sets to examine patterns of gene expression among the samples, and identified genes that were most predictive of survival.

"We found that certain patterns predicted long-term survival and others predicted a poorer prognosis in advanced stage cases," Berchuck said. "Cancers that were detected at an early stage almost always shared gene expression characteristics with advanced stage cases that were long-term survivors, suggesting a shared favorable biology."

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