Long-term multiplication of the Chinese hamster ovary (CHO) cell line in a serum-free medium

A new synthetic medium (referred to as GC3) that supports the growth of the Chinese hamster ovary cell line has been developed. It is composed of a 1:1 mixture of Ham's F12 and modified Eagle's minimum essential (MEM.S) mediums supplemented with transferrin (10 micrograms/ml), insulin (80 mU/ml), and selenium (1 X 10(-7) M). Other more simple supplementations of our basal medium MEM.S/F12 (transferrin + insulin, transferrin + selenium, ferrous iron + selenium) also give good cell growth responses. Fibronectin or serum pretreatment is not needed for cellular attachment and spreading. Our culture system is characterized by a continuous serum-free cultivation (more than 200 doublings), a clonal growth, a high density proliferation, and a rapid growth rate near that of cells in serum-supplemented medium.