Identification and partial characterization of hepatocyte-stimulating factor from leukemia cell lines: comparison with interleukin 1.

Leukemia cell lines of the monocytic series (HL-60, U-937, and P388D1) produce a hepatocyte-stimulating factor (HSF) following induction of differentiation with phorbol diester. In 24-72 hr, these leukemia cells produce 2-30% the amount of HSF as human peripheral blood monocytes. Cells of the series at earlier stages of differentiation produced greater amounts of HSF. Fractionation of the medium from each cell type by HPLC reveals much of the HSF activity in the 25- to 30-kilodalton range. Under the same culture conditions, interleukin 1 is produced; however, its bioactivity is in the 7- to 15-kilodalton range. Neither monokine shows reciprocal bioactivity. Superinducing culture conditions that greatly increase interleukin 1 production completely eliminate HSF production, suggesting that there is different stability of the mRNA coding for each protein or that there are different temporal events important to the induction of synthesis of these proteins.