Role of cofilin­1 in arsenic trioxide­induced apoptosis of NB4­R1 cells.

ABSTRACT

All­trans retinoic acid (ATRA) and arsenic trioxide (As2O3) are currently first­line treatments for acute promyelocytic leukemia (APL). However, a number of patients with APL are resistant to ATRA but still sensitive to As2O3, and the underlying mechanisms of this remain unclear. In the present study, two­dimensional gel electrophoresis, mass spectrometry and other proteomic methods were applied to screen and identify the differentially expressed proteins between the retinoic acid­sensitive cell lines and drug­resistant cell lines. The results demonstrated that in retinoic acid­resistant NB4­R1 cells, the protein expression of cofilin­1 was markedly increased compared with that in the drug­sensitive NB4 cells. Subsequently, the effects of cofilin­1 on As2O3­induced apoptosis in NB4­R1 cells were further investigated. The results revealed that cell viability was markedly suppressed and apoptosis was increased in the As2O3­treated NB4­R1 cells, with increased expression levels of cleaved­poly (ADP­ribose) polymerase and cleaved­caspase 12. Cofilin­1 expression was significantly decreased at both the mRNA and protein levels in the As2O3­treated group compared with the control. Western blotting further revealed that As2O3 treatment decreased the cytoplasmic cofilin­1 level but increased its expression in the mitochondrion. However, the opposite effects of As2O3 on the cytochrome C distribution were found in NB4­R1 cells. This suggested that As2O3 can induce the transfer of cofilin­1 from the cytoplasm to mitochondria and trigger the release of mitochondrial cytochrome C in NB4­R1 cells. Moreover, cofilin­1 knockdown by its specific short hairpin RNA significantly suppressed As2O3­induced NB4­R1 cell apoptosis and inhibited the release of mitochondrial cytochrome C. Whereas, overexpression of cofilin­1 using a plasmid vector carrying cofilin­1 increased the release of cytochrome C into the cytoplasm from the mitochondria in As2O3­treated NB4­R1 cells. In conclusion, cofilin­1 played a role in As2O3­induced NB4­R1 cell apoptosis and it might be a novel target for APL treatment.