Effects of polyunsaturated fatty acids and their n-6 hydroperoxides on growth of five malignant cell lines and the significance of culture media.

We examined effects of polyunsaturated fatty acids (PUFA), their corresponding hydroperoxy fatty acids (hp-PUFA), as well as various pro- and antioxidants on the growth of tumor cells in culture. When cultured in RPMI 1640 medium, A-427 and WEHI clone 13 cells were both highly sensitive to hydroperoxy docosahexaenoic acid (hp-DHA), but they were far less sensitive in minimum essential medium (MEM). In contrast, A-427 cells were also sensitive to DHA in both culture media, while WEHI clone 13 cells, as well as other cell lines, tested in their respective media, were resistant. The lower sensitivity of the cell lines to hp-DHA in MEM-medium was apparently due to a more rapid reduction of hp-DHA to the corresponding hydroxy-DHA in MEM-medium. Addition of glutathione (GSH) to the culture medium abolished the effects of hp-DHA, but not the effects of DHA, while depletion of intracellular GSH levels by L-buthionine-S,R-sulfoximine strongly enhanced the cytotoxic effect of hp-DHA, but not the cytotoxic effect of DHA. alpha-Tocopherol protected A-427 cells against the toxic effect of DHA and abolished the induced lipid peroxidation, while it did not protect against the toxic effects of hp-DHA in A-427 or WEHI clone 13 cells. Ascorbic acid reduced the cytotoxic effect of DHA, but potentiated the toxic effect of hp-DHA while selenite essentially abolished the toxicity of both DHA and hp-DHA. These results indicate that sensitivity of tumor cell lines to PUFA and their oxidation products depends on their antioxidant defense mechanisms, as well as culture conditions, and establishes hp-DHA as a major, but probably not the sole, metabolite responsible for cytotoxicity of DHA.