Differentiation of myeloid cells is accompanied by increased levels of pp60(c-src) protein and kinase activity

Abstract

We have detected a significant increase in the levels of pp60(c-src) kinase activity associated with the differentiation of myeloid cell lines HL-60 and U-937. The induction of pp60(c-src) kinase activity becomes apparent ~14 hr after the addition of phorbol 12-myristate 13-acetate and increases 20-fold by 72 hr. The enhanced kinase activity can be accounted for by elevated levels of c-src protein in the differentiated cells. When nonleukemic bone marrow cells were examined, myeloid progenitor cells exhibited a low level of pp60(c-src) kinase activity. As these cells are allowed to differentiate in culture, the resulting adherent monocytes are as high in pp60(c-src) kinase activity as HL-60 cells induced to differentiate into monocytes. A strong correlation is found between the levels of pp60(c-src) kinase activity and the degree of monocytic differentiation of the cells from patients with acute myeloid leukemia. Our findings suggest that the activation of pp60(c-src) kinase activity is a normal physiological event associated with myeloid differentiation.