Phospholipid compositioncomma; phosphoinositide metabolism and metastatic capacity in murine melanoma B16 variants at different stages of growth

摘要

Experimental efforts to identify characteristic features of metastatic subpulations have led to the selection of strains of specialized cells with high and low metasatatic potential in the hope that by studying their biochemical and biophysical and biophysical properties we might start to clarify how tumour cells metastasize. We report data on thephospholipid compostition of three variants of murine melanoma B16: F1, with low metastatic potential; F10, highly metastatic when injected i.v.; and BL6, highly metastatic, spontaneous metastases developing from a primary s.c. tumour. Cells were studied at different stages of growth: subconfluent cultures (40ndash;70 x 103cells/cm2) or dense cultures (140ndash;170 x 103cells/cm2). Total phospholipid content decreased as cell density increased in all variants; these changes can probably be related to the reduction in cell volume with increasing cell numbers in the well. As a consequence of this reduction, the amounts of individual phospholipids also decreased in dense cultures. Phosphatidylinosital behaved differently in the highly metastatic variants. In the F1 strain it was three times lower than would be expected from the total phospholipid reduction, while in F10 and BL6 levels increased when cell density increased. Differences in phosphatidylinositol level were also found between variants within each density, suggesting that phosphoinositde synthesis may be related to the metastatic potential of the variants. Incorporation of (3Hmyo)-inositol incorporation into phospholipids over a period of 4 h was greater in F1 cells than in F10 and BL6 at both cell densitities. The polyphosphoinositides polyphosphatidylinositol-4-monophosphate (PIP) and phosphatidyliunositol-4,5-biphosphate (PIP2) accounted for 12.8percnt; and 18.5percnt; of phospholipids in confluent and dense cultures of F1 cells respectively, while in F10 and BL6 it was less than 10percnt;. These data suggest that phospho-inositide content may be important in relation to metasatic properites in B16 melanoma variants.