Purification of a Low Molecular Weight Factor That Induces Differentiation and Inhibits Growth in Myeloid Leukemia Cells¹

A procedure is described for purifying a low molecular weight peptide that induces differentiation in mouse myeloid leukemia M1 cells. The factor comes from the conditioned medium of macrophage-like cells differentiated from mouse myeloid leukemia M1 cells. The procedure for purification includes gel filtration on Sephadex G-15, anionic exchange chromatography, thin-layer chromatography, reverse-phase high-performance liquid chromatography on a C₁₈ hydrophobic support, and high-performance liquid chromatography gel filtration. The molecular weight of the factor estimated from the amino acid composition was approximately 1280, which agrees well with that obtained by high-performance liquid chromatography gel filtration. The half-maximal concentration of the purified factor for inducing differentiation of M1 cells was approximately 3.2 × 10^-7 m as judged by nitroblue tetrazolium staining ability. The purified factor also inhibits the growth of human leukemia HL-60 cells.