Changes in Proteolytic Activities of Human Leukemic Promyelocytes (HL-60 Cells) During Maturation

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Abstract
Proteolytic activity was measured in human leukemic promyelocytic cell line (HL-60) grown in culture, before and after the addition of agents which promote differentiation. The 36,000 .times. g soluble fraction of the cells degraded [14C]globin with maximal activity at pH 3.6, while the insoluble fraction had a pH optimum at 8.0. This pattern did not change upon differentiation. Acid protease activity of the soluble fraction increased following differentiation. After 4 days in the presence of dimethyl sulfoxide, the differentiated cells exhibited 4-fold higher specific activity as compared with 4 day-old control cells. Alkaline activity of the insoluble fraction of the differentiated cells was 4-fold lower than that of the undifferentiated cells. Changes in enzyme activities may serve the new functions acquired by the mature granulocytes.