Long-term cultivation and differentiation of human erythroleukemia cells in a protein-free chemically defined medium

To examine whether a human erythroleukemia cell line, K-562, can proliferate and differentiate without protein supplements, long-term cultivation of the cells was carried out in a protein-free chemically defined medium. By the use of stepwise decreases in the fetal bovine serum concentration, continuous growth of K-562 cells was established in a protein-free F-10 medium. The cells have been propagated in this medium for 3 years. The population-doubling time of the cells is about 30 hr. Growth was not stimulated by the addition of insulin, epidermal growth factor, fibroblast growth factor, multiplication-stimulating activity, transferrin, platelet-derived growth factor, or dexamethasone. Addition of serum stimulated the cell growth slightly and increased the saturation density. The saturation density of the cells could be increased to that seen with serum-supplemented cultures by changing the serum-free medium daily. The cells synthesized significant amounts of hemoglobin in the presence of hemin without serum supplementation. The results suggest that the human erythroleukemia cells grown in a protein-free medium do not require serum components for their growth or hemin-induced hemoglobin synthesis and provide an excellent model for better understanding of the growth and differentiation of human leukemia cells.