Isoliquiritigenin induces monocytic differentiation of HL-60 cells

It has been proven that isoliquiritigenin could inhibit the proliferation of some kinds of cancer cell lines and has a strong antioxidative activity. The purpose of this study is to investigate whether the antioxidant isoliquiritigenin affects the proliferation and redifferentiation in HL-60 cells. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) colorimetric method and trypan blue staining were used to measure cell proliferentiation and survival. The morphological changes, nitroblue tetrazolium chloride (NBT) reductive activity, and the CD11b and CD14 surface antigens were used as the biomarkers of redifferentiation of HL-60 cells. The intracellular reactive oxygen species (iROS) level was detected by a fluorescent probe, 2,7-dichlorodihydrofluorescein diacetate (DCFH-DA). Isoliquiritigenin (ISL) inhibited the cell proliferation and decreased the iROS levels in a dose-dependent manner, while the treatment did not increase the lethality rate. After 72 h treatment with 10 microg/ml ISL, a typical differentiated morphology was observed in HL-60 cells, including the decrease of karyoplasmic ratio and the increase of kidney-shape nuclear cells. The positive rate (%) of CD11b (26.4+/-3.90 vs 7.70+/-1.04, P<0.01) and CD14 (20.4+/-2.30 vs 2.63+/-0.133, P<0.01) cells increased significantly. The NBT reductive activity increased 2.3-fold as compared to that of the control group. As an antioxidant, ISL decreased the iROS formation in a dose-dependent manner. All the results indicate that the antioxidant ISL is able to induce the monocytic differentiation in leukemia cells. ISL has the potential as a drug to cure leukemia with fewer side effects.