Growth of rat mammary tumor line 64-24 in liposome-supplemented defined medium. I. Effect of liposome B components on colony growth.

An improved serum-free medium has been developed that supports growth of rat mammary tumor line 64-24 with far less protein supplementation and with a much smaller inoculum than previously possible. An initial survey showed that MCDB 202 supported clonal growth with 1% dialyzed serum. The remaining serum was then replaced with 5 micrograms/ml insulin, 10 ng/ml epidermal growth factor (EGF), 1 micrograms/ml hydrocortisone, 50 ng/ml ovine prolactin, and 5 micrograms/ml liposome B (a mixture of soy lecithin, sphingomyelin, cholesterol, vitamin E, and vitamin E acetate in liposome form). Insulin and EGF are required and growth is improved by hydrocortisone and prolactin. Estradiol is stimulatory in the absence of liposome B. With adequate iron supplementation, transferrin has no effect. Liposome B increases growth rate substantially. Most of the growth stimulation can be replaced with phosphatidylethanolamine or sphingomyelin.