Production and response to an autologous growth factor isolated from human leukemia cells

Human myeloid leukemia HL-60 cells have been shown to release into culture medium an activity that promotes the proliferation of these same HL-60 cells. The presence of additional culture supernatant containing growth-promoter activity accelerates the HL-60 growth rate as determined by cell counts and [3H]thymidine uptake. Isolation of this growth promoter has been performed with the serum-free supernatant of HL-60 cells using salt precipitation, DEAE-Sepharose ion exchange chromatography, and gel electrophoresis. The promoter activity was recovered from SDS-gel electrophoresis within the 60- to 85-kDa mol wt range where a single band of an apparent mol wt of 72,000 was demonstrated. The ability of HL-60 cells to respond to the growth promoter was significantly lost 4 h after exposure to differentiation-inducing activity, while production of the growth promoter was diminished only after 2-3 days following induction of differentiation. These results suggest that the growth-promoting mechanism is associated with the undifferentiated leukemic state. In addition, the role of an autocrine growth mechanism in maintaining the leukemic cells in an undifferentiated state is discussed.