Cell cycle effects of an autologous growth promoter from human leukemia cells

The mechanism of action of an autologous growth promoter, produced by HL-60 cells grown in serum-free defined medium, was investigated. Determinations of cell cycle phase distribution, which showed an approx. 16% increase in S and G2M with a reciprocal decrease in G1 cells, indicated a mechanism causing decreased time in G1, resulting in a more rapid entry of cells into G2M. Adsorption of the culture supernatant with HL-60 cells resulted in a decreased promoter activity, suggesting an autologous receptor mechanism for the promoter.