EFFECTS OF HEXADECYLPHOSPHOCHOLINE ON MEMBRANE PHOSPHOLIPID-METABOLISM IN HUMAN TUMOR-CELLS

Hexadecylphosphocholine (HePC) is an analogue of the antiproliferative alkyllysophospholipds (ALP). As these lipid-like compounds interfere with membrane lipid metabolism at several sites, we studied the effect s of HePC on uptake and metabolism of inositol and choline, two import ant phospholipid precursor molecules in two sensitive cell lines, Pail and KB, and in a resistant variant of KB cells, KBr. HePC substantial ly inhibited the membrane uptake of inositol and of choline in KB and Pail. inositol uptake of KBr cells was constitutively low and was not further decreased by HePC. In all three cell lines, uptake inhibition of choline was less pronounced. Uptake inhibition showed characteristi cs of a non-specific effect, probably due to the physicochemical prope rties of HePC as a ''lyso'' structure. Decreased uptake of inositol di d not affect phosphoinositide synthesis. Cellular phosphatidylcholine (PC) metabolism seemed to be affected through inhibition of choline in corporation and enhancement of PC degradation in the two sensitive cel ls. In KBr cells, these effects were not observed.