Clonal suppression of HL60 and U937 cells by recombinant human leukemia inhibitory factor in combination with GM-CSF or G-CSF.

The in vitro actions of recombinant human leukemia inhibitory factor (LIF) were studied on the human leukemia cell lines HL60 and U937. Parameters analyzed were the suppression of stem cell generation using sequential clonal cultures, alterations of surface antigen expression, and morphological changes. When acting alone, LIF had no observable effects on the number, size, or morphology of colonies formed by HL60 or U937 cells, surface phenotype expression, or recloning capacity of cells of either line. In combination with GM-CSF and G-CSF, however, LIF significantly reduced the number of colonies formed in agar respectively by HL60 and U937 cells. GM-CSF alone greatly reduced the clonogenicity of U937 cells. Using sequential recloning, marked suppression of clonogenicity was observed using combinations of LIF with GM-CSF in HL60 cultures and with G-CSF in U937 cultures. These results suggest that human LIF may have some capacity to suppress human leukemia cells with loss of clonogenicity, at least in combination with G-CSF or GM-CSF.