Apoptosis of retinoic acid-resistant APL NB4-R1 cells induced by As4S4 and its molecular mechanism

Abstract

This study was to investigate the apoptosis-inducing effect of As(4)S(4) on the retinoic acid-resistant acute promyelocytic leukemia (APL) NB4-R1 cells and its potential mechanisms. The leukemia cell line NB4-R1 was cultured in vitro and divided into control group and treatment group. The apoptosis rate and cell cycle were detected by flow cytometry. The apoptotic DNA fragments were analyzed by agarose gel electrophoresis. The changes of BCL-2, BAX and Caspase-3 were determined by Western blot. After NB4-R1 cells were treated with As(4)S(4)(25 µmol/L) for 0 h, 24 h, 48 h, the percentage of early apoptotic cells was obviously raised from 0% to 24.49% and 47.41%, the percentage of late apoptotic cells were elevated from 0.08% to 14.72% and 20.70%. Compared with control group, the DNA degradation revealed a characteristic DNA ladder during agarose gel electrophoresis after treatment for 24 h. The drug significantly induced an accumulation of the S phase cell population from 31.85% of the untreated cells to 42.53% and 55.12% treated with the different time whereas the NB4-R1 cells in G0/G1 phase decreased from 57.30% to 37.56% and 28.51%. As(4)S(4) could decrease the expression of BCL-2 and increase the level of BAX. Pro-caspase-3 could be cleaved into small active fragments under the apoptotic stimulation. As(4)S(4) can efficiently induce NB4-R1 cell apoptosis, which may be related with the down-regulation of BCL-2 and the up-regulation of BAX, as well as the activation of Caspase-3.