Physico-chemical properties of tumor cells that influence their susceptibility to humoral immune killing

Abstract

Line-10 guinea pig hepatoma cells are susceptible to killing by antibody plus human complement, but resistant to killing by antibody plus guinea pig complement. Tumor cells treated with agents that reversibly increase (adriamycin), decrease (insulin or hydrocortisone), or have no effect (5-fluorouracil) on the susceptibility of the cells to antibody-complement killing were tested for their lipid and fatty acid composition. Hormone-treated (resistant) cells showed an increased total lipid content, an increased cholesterol: phospholipid ratio, and a depressed level of unsaturated fatty acids in the cellular neutral and phospholipids compared to control untreated cells. Adriamycin-treated (sensitive) cells showed exactly the opposite effects. The lipid composition of both hormone- and adriamycin-treated cells returned to control levels when the cells reverted to control levels of susceptibility to antibody-complement killing. 5-fluorouracil-treated cells were indistinguishable from untreated controls in their lipid and fatty acid composition. The chemical composition of the cell, and its effects on the physical properties of the cellular membranes, therefore appears to be fundamental for the ability of these tumor cells to resist humoral immune attack.