PROTEIN-KINASE C-BETA IS REQUIRED FOR MACROPHAGE DIFFERENTIATION OF HUMAN HL-60 LEUKEMIA-CELLS

The requirement for protein kinase C (PKC)-beta in phorbol 12-myristat e 13-acetate (PMA)-induced macrophage differentiation of human HL-60 p romyelocytic leukemia cells was studied by using the variant HL-525, w hich is deficient in PKC-beta and is resistant to PMA-induced differen tiation. Transfecting these resistant HL-525 cells with expression vec tors containing either PKC-beta I or PKC-beta II cDNA resulted in clon es that displayed PKC-beta transcript levels similar to or higher than those of the parental HL-60 cells or cells from a PMA-susceptible HL 60 clone, HL-205. These productive transfectants also exhibited PMA-in duced cell attachment and spreading, inhibition of cell replication, r eactivity to the OKM1 monoclonal antibody, and the ability to phagocyt ize opsinized beads, which are all characteristic macrophage markers. No PMA-induced differentiation markers were observed in any of the PKC -beta I or PKC-beta II transfectants that did not exhibit an increased PKC-beta RNA level or in cells transfected with control plasmids. The se results indicate that restoration of the PKC-beta isozyme deficienc y by productive gene transfection causes HL-525 cells to revert to a p henotype like that of the parental HL-60 cells, which is characterized by susceptibility to PMA-induced macrophage differentiation. Therefor e, we can conclude that PKC-beta is one of the essential elements in t he PMA-induced signal transduction pathway which leads to macrophage d ifferentiation in HL-60 cells and perhaps in other related cell types,