Increase of cholesterol level in the surface membrane of lymphoma cells and its inhibitory effect on ascites tumor development.

An ascites form of malignant transformed lymphoma cells were treated in vitro with liposomes of 1:1 lecithin-cholesterol in order to increase the cholesterol level of the cell-surface membranes and thereby to increase the rigidity of the lipid layer. This treatment was found to inhibit the rate of killing by ascites tumor after intraperitoneal inoculation into adult mice of 10(4) and 10(5) treated cells per animal. With 10(3) treated cells per animal, full survival was observed up to 90 days after inoculation, whereas with the same number of untreated cells all infected mice died within 30 days after inoculation. An analogous treatment of the malignant lymphoma cells with liposomes of pure lecithin did not result in any appreciable inhibitory effect on the ascites tumor development in vivo, as initiated by inoculation of 10(5), 10(4), or 10(3) cells per animal.