Effects of specific fatty acids on cell transformation induced by an activated c-H-ras oncogene.

An increase in dietary lipid has been associated with an increase in the development of certain forms of cancer, notably breast and colon cancer, both in experimental animal studies and in human epidemiology studies. The underlying mechanisms are not, however, known with certainty. In the present studies we have examined whether certain specific fatty acids (FA) might act by enhancing the role of an activated oncogene in a model cell culture system. We found that when the rat fibroblast cell line Rat 6 was transfected with an activated human c-H-ras oncogene and the cells subsequently grown in medium supplemented with myristic acid, palmitic acid or stearic acid (20-80 microM) there was a marked enhancement of the number of transformed foci obtained. On the other hand arachidonic acid had a marked inhibitory effect in this transformation assay. However, this inhibitory effect can be partially reversed by indomethacin, an inhibitor of cyclo-oxygenase, at dose response manner. Control studies indicated that these results were not simply due to the effects of the FAs on growth of the Rat 6 cells or the process of transfection per se. Lipid analyses of cells grown in the presence of stearic acid indicated that the added FA was extensively incorporated into the major lipid classes of the cell and produced transient changes in lipid composition. This simple cell culture system may be useful for elucidating the mechanisms by which various dietary lipids and nutritional factors influence the carcinogenic process.