OBJECTIVETo determine whether a novel compound, 3-(4-bromophenyl)-2-(ethyl sulfonyl)-6-methylquinoxaline 1, 4-dioxide (Q39), induces apoptosis in human leukemia cell line k562 in hypoxic environment.

METHODSMTT assay was used to determine the 50% inhibitory concentrations (IC50). Flow cytometry and DAPI staining were employed to determine the apoptosis; JC-1 staining was used to determine mitochondria membrane potential (DeltaPsim); Western-blotting was used to determine protein expression of procaspase-3, cleaved caspase-3, PARP, Bax, Bcl-2 and HIF-1alpha.

RESULTSIn hypoxic environment, Q39 exerted higher antiproliferative activity in K562 cells, and the IC50 value was (0.21+/- 0.05) micromol/L. The apoptotic phenomenon was observed at 6 h after cells exposed to Q39, and apoptotic body emerged as exposure time increased. After K562 cells were incubated with Q39 for 0, 6, 12 and 24 h, the ratio of apoptotic cells was 2.8%, 3.2%, 5.9% and 19.2%, respectively. By fluorescence stain assay, an significant Delta Psim loss in K562 cells induced by Q39 was shown in a time-dependent manner. Western blot assay demonstrated that Q39 decreased the protein expression of Bcl-2, procaspase-3, and HIF-1alpha, meanwhile increased protein expression of Bax and cleaved caspase-3, and induced the cleavage of PARP.

CONCLUSIONSThe novel compound Q39 exhibits great anticancer activity against K562 cells in hypoxic environment. Q39 can downregulate the protein expression of HIF-1alpha, and regulate the apoptosis-related protein expression to cause a drop of DeltaPsim, suggesting that mitochondria and HIF-1alpha pathway might be involved in the antiproliferative effect of Q39.