Pattern of colony-stimulating activity in HL-60 cells after phorbol-ester-induced differentiation.

HL-60 cells secrete an autostimulatory activity (ASA) that appears to be required for their growth in vitro. The purpose of this study was to examine the pattern of colony-stimulating activity in conditioned media of HL-60 after induction of differentiation by the phorbol ester phorbol-12-myristate-13-acetate (PMA). PMA-induced differentiation to monocyte-macrophage cells was accompanied by persistence of ASA secretion and the appearance of new species of colony-stimulating activities similar in properties to human CSF I and CSF II. Thus the secretion of ASA by HL-60 appears to be a characteristic property of these cells that is maintained after terminal differentiation.