Alteration of p60c-src expression in human leukemia-lymphoma cells correlated with induced differentiation

Expression of cellular src-gene product (p60c-src) in human leukemia-lymphoma cell lines was analysed by flow cytometry using a monoclonal antibody (McAb), H2B4 which recognizes p60c-src protein in human cells. In several human leukemia-lymphoma cell lines (K562, Namalva, HL60, U937), p60c-src expression was higher than in peripheral mononuclear cells from healthy volunteers. Some non-lymphoid leukemia cells can be induced to differentiate into monocyte-macrophages by 12-O-tetradecanoyl phorbol-13-acetate (TPA). K562 cells were also induced to differentiate not only morphologically but also functionally into monocyte-macrophages by TPA. Flow cytometric analyses using the McAb H2B4 revealed that the amount of p60c-src expression in K562 cells markedly decreased during TPA induced differentiation. The activity of protein kinase associated with p60c-src in K562 cells was determined employing IgG of immunized rabbit serum specific for p60c-src. The immunized rabbit IgG heavy chain phosphorylation by protein kinase also decreased after the induced differentiation. We detected p60c-src protein in acute lymphoid leukemia cells as well as acute non-lymphoid leukemia cells freshly isolated from patients. The amount of p60c-src protein decreased in some acute non-lymphoid leukemia cases, but it increased in others after TPA induced differentiation. No correlation was observed between FAB classification of acute leukemias and the amount of endogenous p60c-src expression.