Abstract
Little is known regarding the membrane properties of metastatic cells as compared to non-metastatic tumor cells. In order to remove variables such as site of growth and nutrition. C 3H mice and LM fibroblasts were used as a model system to derive cell lines from local tumors and lung metastases. LM cells were injected subcutaneously into C 3H mice and local skin tumors and secondary lung tumors were isolated, cultured in vitro and analyzed. The activities of lipid-sensitive membrane enzymes, membrane lipid composition, and membrane structure were correlated with metastatic ability. Plasma membranes and microsomes of the cultured metastatic cells had 3.8 ± 0.5- and 5.4 ± 0.6-fold elevated 5′-nucleotidase activity, respectively, as compared to plasma membranes and microsomes of cultured non-metastatic cells. The mitochondria of cultured metastatic cells had 3.5 ± 0.5-fold decreased succinate-dependent cytochrome- c reductase activity as compared to mitochondria of the cultured non-metastatic cells. The lipids of plasma membranes from the metastatic cells had 30 ± 2% and 46 ± 7% lower phosphatidylinositol and sterol/phospolipid ratio, respectively, and 30 ± 3% increased unsaturated/saturated fatty acid as compared to cultured non-metastatic cells. The lower sterol/phospholipid ratio correlated with a 30 ± 1% lower level of cytosolic sterol carrie protein in the cultured metastatic cells as compared to cultured non-metastatic cells. Multifrequency phase and modulation fluorometry in conjunction with the fluorescence probe, 1,6-diphenyl-1,3,5-hexatriene, was used to determine the static and dynamic aspects of membrane fluidity. The plasma membranes and microsomes of cultured metastatic cells were more fluid than those of cultured non-metastatic cells as indicated by 24 ± 3% and 7 ± 1%, respectively, lower limiting anisotropy of 1,6-diphenyl-1,3,5-hexatriene in the membranes of the metastatic as compared to non-metastatic cells.
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