Changes in susceptibility to Fas-mediated apoptosis during differentiation of HL-60 cells

The Fas-mediated pathway has been implicated as an important cellular pathway mediating apoptosis in diverse cell types. We conducted studies to examine the susceptibility to Fas-mediated apoptosis of HL-60 cells treated with differentiation-inducing factors such as dimethyl sulfoxide (DMSO), retinoic acid (RA), and 1alpha, 25 dihydroxyvitamin D3 (VD3). Although the expression of Fas antigen (Ag) and its mRNA showed a marked increase in HL-60 cells with cell differentiation, that of Bcl-2 protein and its mRNA revealed the reverse. The expression of caspase proteins such as caspases-3 and -8 was also enhanced during cell differentiation. DNA fragmentation, annexin V binding, and caspase activities increased in differentiated HL-60 cells with the addition of anti-Fas Ag antibody. These findings were more clearly demonstrated in DMSO- or RA-induced neutrophil-like cells than in VD3-induced monocyte-like cells. Therefore, susceptibility to Fas-mediated apoptosis showed an increase with differentiation of HL-60 cells, especially in the neutrophil lineage. These results suggest that the difference of susceptibility to Fas-mediated apoptosis among cell populations depends on the expression of Fas Ag, Bcl-2, and caspases. Cell maturation and susceptibility to Fas-mediated apoptosis may be linked in hematopoietic cells.