Effects of fatty acid modification of ascites tumor cells on pulmonary metastasis in rat.

Yoshida sarcoma cells were incubated with each of 4 different saturated and 17 different unsaturated fatty acid methyl and ethyl esters in order to modify the fatty acid composition of the cell membrane, and a possible correlation between the lipid fluidity of the cell membrane and the metastatic efficiency was studied. Almost all the unsaturated fatty acids used were incorporated into the tumor cell membrane, resulting in an increase of fluidity. In contrast, the incorporation of saturated fatty acids brought no change in fluidity. Exogenous treatment of the cells with palmitoleic acid (16:1, cis) induced a remarkable increase of membrane lipid fluidity resulting in easier passage of modified cells through capillary vessels, which was detected in an in vitro perfusion test of the lung. Intravenous injection of the modified cells resulted in fewer metastatic foci in the lung as compared with that of unmodified cells. A similar effect on lung metastasis was also observed in exogenous modification of the cells by linoleic acid (18:2, cis) or linolenic acid (18:3, n-3). On the other hand, although exogenous eicosapentaenoic acid (20:5, n-3) and docosahexaenoic acid (22:6, n-3) treatments induced a slight increase in the lipid fluidity of the cells, intravenous injection of the cells produced a significant increase in their metastatic potential in the lung. Interestingly, the treatment with 20:5 and 22:6 produced increased stickiness of the cells to a glass surface and reduced cellular passage through the vessels as detected by the lung perfusion test. Thus, the present results suggested that selective modification of membrane fatty acid may be a useful method for artificial regulation of the ability of circulating tumor cells to pass through vessels.