Induction of human HL-60 leukemic cell differentiation by immune interferon is accompanied by an increase in NADase...

The effects of highly purified human immune interferon (IFN-gamma) on the differentiation of human promyelocytic HL-60 leukemic cells have been studied. The addition of 100 units/ml interferon to HL-60 cells for 5 days results in morphological changes characteristic of macrophages. At the biochemical level, there is a 3-fold increase in the specific activity of the enzyme NADase. Kinetic analysis shows that IFN-gamma causes an increase in the Vmax of NADase without affecting the apparent Km. Pulse labeling experiments with [35S] methionine show a marked change in the de novo synthesis of several proteins in the course of interferon treatment. Chromatography on DNA-agarose show that after treatment with interferon for 24 or 48 h, there is a 60-70% decrease in newly synthesized proteins which bind DNA-agarose and can be subsequently displaced from the column with 2% SDS containing buffer (from 7.7-8.7% bound in control cell extracts to 2.6-3.1% bound in interferon treated cell extract).