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MicroRNA 145 may play an important role in uveal melanoma cell growth by potentially targeting insulin receptor substrate‐1

Background MicroRNAs (miRNAs) contribute to tumorigenesis by acting as either oncogenes or tumor suppressor genes. In this study, we investigated the role of miR‐145 in the pathogenesis of uveal melanoma. Methods Expression profiles of miRNAs in uveal melanoma were performed using Agilent miRNA array. Quantitative real‐time polymerase chain reaction was used to screen the expression levels of miR‐145 in normal uveal tissue, uveal melanoma tissue, and uveal melanoma cell lines. Lenti‐virus expression system was used to construct MUM‐2B and OCM‐1 cell lines with stable overexpression of miR‐145. Cell proliferation, cell cycle, and cell apoptosis of these miR‐145 overexpression cell lines were examined by MTT assay and flow cytometry respectively. The target genes of miR‐145 were predicted by bioinformatics and confirmed using a luciferase reporter assay. The expression of insulin‐like growth factor‐1 receptor (IGF‐1R), insulin receptor substrate‐1 (IRS‐1) proteins was determined by Western blotting analysis. IRS‐1 was knocked down in OCM‐1 cells. TUNEL, BrdU, and flow cytometry assay were performed in IRS‐1 knocked down OCM‐1 cell lines to analyze its function. Results Forty‐seven miRNAs were up regulated in uveal melanoma and 61 were down regulated. miR‐145 expression was significantly lower in uveal melanoma sample and the cell lines were compared with normal uveal sample. Overexpression of miR‐145 suppressed cell proliferation by blocking the G1 phase entering S phase in uveal melanoma cells, and promoted uveal melanoma cell apoptosis. IRS‐1 was identified as a potential target of miR‐145 by dual luciferase reporter assay. Knocking down of IRS‐1 had similar effect as overexpression of miR‐145. Conclusion miR‐145 might act as a tumor suppressor in uveal melanoma, and downregulation of the target IRS‐1 might be a potential mechanism.