Tumor Necrosis Factor-a Enhances Human Leukemia Cell Differentiation Induced by DMSO, but Not Retinoic Acid.

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.