Protein phosphatase 1, regulatory subunit 13 like PPP1R13L, also coined iASPP, was found high expression in prostate cancer tissues and cell lines.In previous research, in vitro and in vivo RNAi mediated by artificial lentiviralshRNAs which proved that suppression of iASPP decrease the proliferation of cancer cells.Endogenous interference RNAs, microRNAs play key roles in cell proliferation by post-transcriptional regulation of gene expression.Natural base pair matched microRNA for iASPP is mir124, which was found high expression in growth factor-loss prostate cancer cell lines.In this study we examined effect of mir124 upon iASPP and proliferation of prostate cells in vitro with lentiviral infection and use artificial shRNA as control.In vitro reporter assay confirmed that mir124 binding the 3UTR of iASPP and suppress mRNA expression.Lentivirus mediated mir124 expression decreased the proliferation and viability of PC3 while endogenous iASPP were knocked down.