Membranes of high- and low-metastatic L tumor cell variants

A model system of metastasis, L-929 fibroblasts and a derivative cell line, A-9 cells, was developed in order to compare the membrane properties of high- and low-metastatic cells cultured in chemically defined medium. The metastatic ability of L-929 and A-9 cells in athymic (nude) mice was examined. Both cell lines produced local tumors, but only L-929 fibroblasts metastasized to the lung. The plasma membranes of L-929 cells had lower sterol/phospholipid ratios and their phospholipids were more unsaturated than those of A-9 cells. The fluorescence probe 1,6-diphenyl-1,3,5-hexatriene and multifrequency phase and modulation fluorometry indicated that the plasma membranes of L-929 cells were less rigid (lower polarization and limiting anisotropy; shorter rotational relaxation time and lifetime) than those of A-9 cells. Thus, the membranes of highly metastatic cells had more unsaturated fatty acids, a lower sterol/phospholipid ratio and were consequently less ordered than those of their less malignant counterparts that formed only local tumors.