Commitment of neutrophilic differentiation and proliferation of HL-60 cells coincides with expression of transferrin receptor - Effect of granulocyte colony stimulating factor on differentiation and proliferation

To examine the regulatory mechanisms of proliferation and maturation in neutrophilic lineage cells, we have tried to sort dimethyl sulfoxide (Me2SO)-treated HL-60 cells into transferrin receptor (Trf-R) positive (Trf-R+) and negative (Trf-R-) cells. Differentiated Trf-R- cells expressed more formyl-Met-Leu-Phe receptor (fMLP-receptor) and ability of O(2)radical anion genaration, as markers of differentiation, than Trf-R+ cells, and Trf-R cell differentiation was markedly accelerated by the incubation with granulocyte colony stimulating factor (G-CSF), On the other hand, Trf-R+ cells had a tendency to proliferate rather than differentiate, and proliferation was enhanced by G-CSF, These results indicate that Trf-R expression coincides with the commitment to proliferate or differentiate of HL-60 cells, and G-CSF accelerates these commitments. G-CSF-induced tyrosine phosphorylation of STAT 3 in Trf-R- cells much more than in Trf-R+ cells. Protein 70 S6 kinase expression was higher in Trf-R+ cells than in Trf-R- cells. Furthermore, p70 S6 kinase was hyperphosphorylated by G-CSF in Trf-R+ cells, but not in Trf-R- cells. Rapamycin, an inhibitor of p70 S6 kinase activity, inhibited G-CSF-dependent proliferation of Trf-R+ cells and increased fMLP-R expression on these cells. These results suggest that commitment to proliferation and differentiation in Me2SO-treated HL-60 cells is preprogrammed and correlated with Trf-R expression, and G-CSF potentiates the cellular commitment. STAT 3 may promote differentiation of Me2SO-treated HL-60 cells into neutrophils, while p70 S6 kinase may promote proliferation and negatively regulate neutrophilic differentiation.