Lipid metabolism in cultured cells: growth of tumor cells deficient in essential fatty acids.

di-cis-decadienyl structure are apparently required for maintenance of normal growth and reproduction (16). The commonly occurring fatty acids exhibiting this structural moiety are linoleic (18 :2w6)', linolenic (1 8:3w3), and arachidonic acids (20:4co6). Since they are not synthesized de novo, they have been termed the â€oeEFA's.†• 2 A dietary requirement for these fatty acids has been shown to exist in all 11 species of experimental animals so far tested. Differences apparently exist, however, in the absolute requirement for EFA at the cellular level. In 1963, Ham (9) reported that in vitro cultures of Chinese hamster strain CHD-3 cells in synthetic medium require linoleic acid for normal plating efficiency. More recently, Gerschenson et aL (7) reported lack of growth and certain metabolic defects as characteristics of HeLa 53 cells cultured in a lipid-deficient medium. These effects were partially reversed by linoleic acid. In contrast to these findings, Smedley-MacLéan and Nunn (1 5), in 1941 , observed that the Walker 256 carcinoma grew as well when implanted in fat-starved rats as in those receiving a daily dose of linseed oil. In addition, a number of cell lines, including the L2071 strain of mouse fibroblast, have been adapted to a lipid-free, chemically defined medium by Evans et al. (6) since 1956. The linoleic acid content of L strain fibroblasts grown in the lipid-free synthetic medium was found to be about 6% of the total fatty acids (2). This compared with a content of about 25% linoleic acid when grown on serum-supplemented medium. It was shown by supplementing the lipid-free medium with @ C that the residual linoleic acid was not the result of de novo synthesis, but instead represented the operation of an efficient scavenging process by the cells for traces of linoleic acid present as contaminants in the culture environment. Geyer (8) has reported that the linoleic acid is completely depleted in rapidly growing L-cells. Laboratory mice readily display symptoms of EFA deficiency when placed on a fat-free diet. The linoleic acid content of serum lipids falls to very low levels in only a few weeks. A number of rapidly dividing tumor cell lines which grow in the ascitic form in the peritoneal cavity of mice are available. The present work was undertaken to study the growth and composition of such rapidly dividing cells in the EFA-deficient environment provided by host mice maintained on fat-free diets. SUMMARY Certain strains of cells …