MicroRNA-145 directly targets the insulin-like growth factor receptor I in human bladder cancer cells

•miR-145 levels are decreased in human bladder cancer cells.•miR-145 expression affects IGF-IR levels and IGF-I-induced cell viability.•miR-145 promotes apoptosis and suppresses migration in T24 cells.•Silencing of IGF-IR increases cell apoptosis and inhibits proliferation and migration.•miR-145 functions as a tumour suppressor through repression of oncogenic IGF-IR. The insulin-like growth factor receptor I (IGF-IR) is a proto-oncogene with potent mitogenic and antiapoptotic activities. It has been reported that expression of IGF-IR is up-regulated in bladder cancer. Here, we assessed whether microRNA-145 (miR-145) regulates IGF-IR expression in bladder cancer. In our study, miR-145 was shown to directly target IGF-IR 3′-untranslated region (UTR) in human bladder cancer cells. Small interfering RNA (siRNA)- and miR-145-mediated IGF-IR knockdown experiments revealed that miR-145 promotes cell apoptosis, and suppresses cell proliferation and migration through suppression of IGF-IR expression. Taken together, our data suggest that miR-145 may inhibit bladder cancer initiation by affecting IGF-IR signaling.