The scientists, led by Kathryn Meier of Washington State University, say they had discovered a new mechanism by which omega-3 fatty acids - eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) – halt the proliferation of cancer cells. They bind to a receptor called FFA4 or ‘free fatty acid receptor 4,’ which in turn acts as a signal to inhibit cancer cell growth.
Meier said: “We're the first to show that [omega-3s] work this way in cancer. The attention has mostly been on inflammation and diabetes but there has always been an interest in cancer, and we were the first to show this mechanism in any cancer cell at all. And we're using prostate cancer, which is the most controversial subject in omega 3s."
These results conflict with a 2013 study, published in the Journal of the National Cancer Institute, which found that high blood concentrations of long chain omega-3 polyunsaturated fatty acids (PUFAs) led to a 71% higher risk of developing high-grade prostate cancer. At the time, chief researcher Alan Kristal claimed that this had "once again" showed that nutritional supplements may be harmful, provoking a backlash from both industry insiders and other leading scientists.
The Washington State University researchers recognised that the benefit of omega-3s on prostate cancer was "quite controversial" but said that it was worthy of further investigation. They said their findings had been unexpected.
The study
Prostate cancer cells were first treated with lysophosphatidic acid (LPA) to activate the cancer cells, with EPA or DHA then added.
The scientists found that if added before the LPA, EPA but not DHA reduced the number of viable cancer cells at 48 and 72 hours. The rapidity of EPA effect suggested that it had activated the FFA4, which then bound to omega-3 fatty acids and inhibited cancer cell growth.
“This study presents unexpected findings showing that omega-3 fatty acids and FFA4 agonists can inhibit growth factor–induced signalling. To our knowledge, ours is the first study to examine the roles of FFA4 in prostate cancer cells.”
Potential for a new drug?
Meier has said the results had “important implications for the administration of n-3 fatty acid supplements or FFAR agonists with the intention of preventing cancer”.
However she called for more research into the dosage required, suggesting that to fight an existing cancer it may be more efficient to isolate the pharmacodynamic properties of omega-3s and create a new drug, rather than supplementing with omega-3s.
"It's very difficult in dietary studies to tell how much to take or what form to take. Should you be eating fish? Should you be taking pills? But now we have a potential drug. Once you have a drug you can test very precisely whether it works or not in a certain disease and you would know exactly how much to give people," she said.
Source: The Journal of Pharmacology and Experimental Therapeutics
PublishedFebruary 2015, iss. 352, pp. 380–394, http://dx.doi.org/10.1124/jpet.114.218974
Omega-3 Fatty Acids and Other FFA4 Agonists Inhibit Growth Factor Signaling in Human Prostate Cancer Cells
Authors: K. Meier, Z. Liu, M. M. Hopkins et al.