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Fish oil reduces effectiveness of chemotherapy

September 12, 2011
University Medical Center Utrecht
The body produces a substance that renders cancer cells insensitive to treatment with widely used chemotherapies. The same substance is also contained in fish oil capsules that are taken by many cancer patients. The Dutch researchers who discovered the substance advise patients undergoing chemotherapy against the use of fish oil and similar products.

Researchers at University Medical Center Utrecht, the Netherlands, have discovered a substance that has an adverse effect on nearly all types of chemotherapy -- making cancer cells insensitive to the treatment. Chemotherapy often loses effectiveness over time. It is often unclear how or why this happens.

It now appears that chemotherapy is made ineffective by two types of fatty acid that are made by stem cells in the blood. Under the influence of cisplatin chemotherapy, the stem cells secrete these fatty acids that induce resistance to a broad spectrum of chemotherapies. These substances are referred to by researchers as 'PIFAs' which stands for platinum-induced fatty acids. Cisplatin is a type of chemotherapy that is widely used for the treatment of cancer, including cancer of the lungs and ovaries.

Tumors under the skin

The researchers studied the effect of PIFA's in mice and human cells. The mice studied had tumors under the skin. Under normal conditions, the tumors would decrease in size following the administration of chemotherapy. In the study, after administering the fatty acids to the mice, the tumors were found to be insensitive to chemotherapy. The fatty acids were isolated from the medium in which chemotherapy exposed stem cells were grown. But also stem cells in the blood of patients produce the fatty acids that desensitize tumors to chemotherapy.

The fatty acids are also found in commercially-produced fish oil supplements containing omega-3 and omega-6 fatty acids as well as in some algae extracts. In the experiments conducted in mice, the tumors became insensitive to chemotherapy after administration of normal amounts of fish oil. Natural products that include fish oil are frequently used by cancer patients in addition to their regular treatment.

"Don't use these products"

Professor Emile Voest, a medical oncologist at UMC Utrecht, supervised the research. "Where resistance to chemotherapy is concerned, we usually believe that changes in the cancer cells themselves have occurred. Now we show that the body itself secretes protective substances into the blood that are powerful enough to block the effect of chemotherapy. These substances can be found in some types of fish oil. Whilst waiting for the results of further research, we currently recommend that these products should not be used whilst people are undergoing chemotherapy."

Researchers at the University Medical Center Utrecht, the Netherlands, describe these findings, that will appear online on September 12, in the journal Cancer Cell.

Story Source:

The above post is reprinted from materials provided by University Medical Center Utrecht. Note: Materials may be edited for content and length.

Journal Reference:

  1. Jeanine M.L. Roodhart, Laura G.M. Daenen, Edwin C.A. Stigter, Henk-Jan Prins, Johan Gerrits, Julia M. Houthuijzen, Marije G. Gerritsen, Henk S. Schipper, Marieke J.G. Backer, Miranda van Amersfoort, Joost S.P. Vermaat, Petra Moerer, Kenji Ishihara, Eric Kalkhoven, Jos H. Beijnen, Patrick W.B. Derksen, Rene H. Medema, Anton C. Martens, Arjan B. Brenkman, Emile E. Voest. Mesenchymal Stem Cells Induce Resistance to Chemotherapy through the Release of Platinum-Induced Fatty Acids. Cancer Cell, 2011; 20 (3): 370 DOI: 10.1016/j.ccr.2011.08.010

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University Medical Center Utrecht. "Fish oil reduces effectiveness of chemotherapy." ScienceDaily. ScienceDaily, 12 September 2011. <>.
University Medical Center Utrecht. (2011, September 12). Fish oil reduces effectiveness of chemotherapy. ScienceDaily. Retrieved October 9, 2015 from
University Medical Center Utrecht. "Fish oil reduces effectiveness of chemotherapy." ScienceDaily. (accessed October 9, 2015).

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