A new study has reported that two fatty acids found in some fish oil supplements can induce resistance to chemotherapy. Immediate or eventual resistance to chemotherapy is a major obstacle to lasting effective treatment of cancer. In the study, the authors demonstrate that mesenchymal stem cells become activated by these fatty acids during treatment with platinum-based chemotherapy drugs and secrete factors that can protect cancer cells against a range of chemotherapy drugs.

Mesenchymal stem cells are adult stem cells (found primarily in bone marrow) which can differentiate into a variety of cell types. Platinum-based chemotherapy drugs include cisplatin (Platinol), carboplatin (Paraplatin), and oxaliplatum (Eloxatin).

The authors identified two distinct platinum-induced polyunsaturated fatty acids, 12-oxo-5,8,10-heptadecatrienoic acid (KHT) and hexadeca-4,7,10,13-tetraenoic acid (16:4(n-3)), by investigating how platinum chemotherapy is metabolized. The two fatty acids were found to induce resistance to a broad spectrum of chemotherapy drugs in minute quantities. Furthermore, blocking important enzymes involved in the production of these fatty acids prevents mesenchymal stem cell-induced resistance. These two fatty acids can be found in some types of fish oil. In additional tests using mice with tumors under the skin, the authors found that animals injected with the fatty acids, described as "normal amounts of fish oil," became insensitive to chemotherapy. The authors conclude that the study results show that mesenchymal stem cells are potent mediators of resistance to chemotherapy.

Comments regarding the study

The finding that two fatty acids found in small amounts in some fish oil supplements can block chemotherapy's intended effects is alarming. Unfortunately, consumers are not in a position to know which fish oils contain these fatty acids. In a separate interview, Emile Voest, a medical oncologist who supervised the research, commented that "whilst waiting for the results of further research, we currently recommend that these products should not be used whilst people are undergoing chemotherapy."

Please see our article on how to optimize your breast cancer diet for information on what to eat during all stages of treatment and recovery.