Arsenic trioxide induced apoptosis in retinoblastoma cells by abnormal expression of microRNA-376a.

Arsenic trioxide (ATO) has been demonstrated to induce apoptosis in retinoblastoma cells, however, mechanisms responsible for this phenomenon are not fully understood. In the present study, we determined whether ATO induced apoptosis by abnormal expression of microRNA. In an apoptosis model of retinoblastoma cells subjected to 4 μM ATO for 72 hours, we found 14 miRNAs changed more than 2-fold by using miRNA microarray analysis. Most of these aberrantly expressed miRNAs were confirmed by quantitative RT-PCR. MiR-376a, a significantly down-regulated miRNA, was selected for further study. The overexpression of miR-376a resulting from miR-376a mimic transfection significantly inhibited ATO-induced apoptosis. By contrast, miR-376a deficiency resulting from miR-376a inhibitor transfection aggravated ATO-induced apoptosis. Using bioinformatic algorithms, caspase-3, a key apoptosis executioner, was predicted as a putative target of miR-376a. The quantitative RT-PCR showed no effects of miR-376a mimic or inhibitor on caspase-3 mRNA level. However, the amount of caspase-3 proteins was reduced by miR-376a mimic, whereas increased by miR-376a inhibitor. Furthermore, the luciferase reporter assay confirmed caspase-3 to be a target of miR-376a, and the apoptosis caused by miR-376a inhibitor were abolished by a caspase-3 inhibitor. These results suggest that ATO -induced apoptosis in retinoblastoma cells is part mediated by decreasing expression of miR-376a, which subsequently increased caspase-3 expression.