Susceptibility of mammary tumor cells to complement-mediated cytolysis after in vitro or in vivo fatty acid manipulation.

The susceptibility of line 168 murine mammary tumor cells to complement (C)-mediated lysis was tested after in vitro treatment with several saturated or unsaturated fatty acids dissolved in different solvents or presented in the form of micelles to the cells. The lytic susceptibility of these cultured cells was compared with similar tumor cells obtained either from mice maintained on diets containing different concentrations and saturations of fatty acids or from cultures supplemented with serum from tumor-free control mice fed pair-matched diets. Although changes in dietary fat concentration and saturation resulted in alterations of the tumor cell fatty acid composition, those alterations did not influence the susceptibility of tumor cells to C-mediated lysis. However, single, or combinations of, unsaturated fatty acids dissolved in ethanol, unlike saturated fatty acids, reduced the lytic susceptibility of tumor cells in vitro. Hexane added to culture medium significantly suppressed the lytic susceptibility; however, when used as a carrier no significant differences were observed among treatments with the individual fatty acids at several concentrations. This result may be due to the effect of hexane on the cell membrane because this treatment also affected the osmotic fragility of the cells. Fatty acids as micelles did not influence the susceptibility of tumor cells to lysis. We concluded that only in vitro manipulation of fatty acids in some vehicles influenced the susceptibility of target tumor cells to C-mediated lysis; this finding did not parallel the situation that occurred in vivo. Moreover, the use of different vehicles to present fatty acids to tumor cells may further alter the susceptibility to C-mediated lysis.