Abstract
One of the human leukemia treatment methods is to differentiate leukemia cells into mature cells. Because differentiated cells lose their proliferative and tumor-forming abilities, differentiation inducers may be useful for the treatment of leukemia. Differentiation of leukemia cells has been studied using HL60 cells, a human promyelocytic leukemia cell line, which can be differentiated into granulocyte-like or monocyte/macrophage-like cells by various pharmacological agents such as dimethyl sulfoxide (DMSO), retinoic acid and phorbol myristic acetate (PMA). We previously reported that nuclear factor - kB (NF-kB) activation plays the important role in DMSO-induced differentiation of HL60 cells. Thus, we hypothesized that NF-kB activators could enhance DMSO-induced differentiation of HL60 cells. Here we examine whether tumor necrosis factor-a (TNF-a), a potent NF-kB inducer, enhance DMSO-induced differentiation of HL60 cells. TNF-a was found to enhance HL60 cell differentiation induced by DMSO. CD11b, a differentiation marker, was increased in 0.5 % DMSO-treated cells compared to control cells. When TNF-a was added to the same condition, CD11b expression was further enhanced in a dose and a time dependent manners. We also found that nitro blue tetrazolium (NBT) reducing activity, a marker for granulocytic differentiation, was further increased in DMSO plus TNF-a treated cells compared to only DMSO- treated cells. However, TNF-a alone had no effect on CD11b expression and NBT reducing activity. The enhancement of DMSO-induced HL60 differentiation by TNF-a was offset by NF-kB inhibition. Interestingly, retinoic acid- induced differentiation of HL60 cells showed no enhancing effect of TNF--a on the differentiation. These findings indicate that TNF--a might affect only NF-kB dependent differentation of HL60 cells. Taken together, we demonstrated that TNF-a enhances DMSO-induced differentiation of HL60 cells by stimulating NF-kB activation. Our results suggest that NF-kB inducers such as TNF-a are useful for the treatment of leukemia in combination with DMSO.
Colony stimulating factor-induced differentiation of murine M1 myeloid leukemia cells is permissive in early G1 phase.