To examine the regulatory mechanisms of proliferation and maturation in neutrophilic lineage cells, we have found the existence of transferrin receptor (Trf-R) positive (Trf-R+) and negative (Trf-R-) cells in DMSO-treated HL-60 cells and successfully sorted into Trf-R+ and Trf-R- cells. Differentiated Trf-R- cells exhibited much more maturation of neutrophilic cells as compared with Trf-R+ cells, and G-CSF accelerated differentiation of Trf-R- cells. On the other hand, Trf-R+ cells had a tendency to proliferate rather than differentiate, and proliferation has enhanced by G-CSF. These resullts indicate that Trf-R expression coincides with the commitment to proliferate or differentiate of HL-60 cells, and G-CSF accelerates these commitments. On the basis from the results of G-CSF-induced signal transduction in Trf-R+ and Trf-R- cells, STAT 3 promoted the differentiation of HL-60 cells into neutrophils, while p 70 S6 kinase promotes proliferation and negatively regulate neutrophilic differentiation.
We also examined cross talk of G-CSF and GM-CSF on the differentiation of HL-60 cells into nuetrophils. While G-CSF accelerate the neutrophilic differentiation of DMSO-treated HL-60 cells, GM-CSF markedly inhibited the G-CSF induced enhancement of neutrophilic differentiation. Furthermore, GM-CSF did not alter the G-CSF induced tyrosine phosphorylation of STAT 3, but GM-CSF inhibited the nuclear translocation of tyrosine-phosphorylated STAT 3. Therefore, we concluded that G-CSF-dependent nuclear translocation of STAT 3 coordinates with the promotion of neutrophilic differentiation in DMSO-treated HL-60 cells.
