The potential differential effects of polyunsaturated fatty acids (5-100 mu g/ml) on four human tumour cell lines of different origin and a human fibroblast cell line were investigated. Following 6 days exposure to the fatty acids, gamma linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid, culture growth was almost completely abolished at the highest concentration used. At lower concentrations, the tumour cell lines exhibited a differential sensitivity to the inhibitory effects of the fatty acids on cell number (IC50, breast=lung>melanoma>colon). MRC-5 fibroblast cell numbers were significantly increased at low concentrations of gamma linolenate and eicosapentaenoate, but significantly reduced by docosahexaenoate. These effects on cell numbers were rapid in onset. Following only 2 days exposure to low concentrations of the fatty acids, cell numbers in the breast tumour cell line, MCF-7, were significantly reduced relative to controls. In contrast, the colon cell line, WiDR, was largely unaffected at this time, and in some cases, cell numbers were significantly increased. In the normal fibroblast cell line, cell numbers were significantly reduced by docosahexaenoate at concentrations greater than or equal to 20 mu g/ml. Following only 2 days exposure to PUFA, cell death in the breast cell cultures was maximally increased above controls by 20 mu g/ml of docosahexaenoate, whereas cell proliferation was unaffected at this concentration. In contrast, under these circumstances, cell proliferation in the colon cell cultures was significantly increased by this PUFA while there were only small increases in cell death. Our observations have highlighted the differential responses of human tumour cell lines to PUFAs and documented the stimulation of a colon cell line by certain PUFAs.

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