Our expression signatures of human cancer including bladder cancer (BC) revealed that the expression of microRNA-1 (miR-1) and microRNA-133a (miR-133a) is significantly reduced in cancer cells. In the human genome, miR-1 and miR-133a are located on the same chromosomal region (miR-1-2 and miR-133a-1 on 18q11.2, and miR-1-1 and miR-133a-2 on 20q13.33) called cluster. In this study, we identified the novel molecular targets commonly regulated by miR-1 and miR-133a in BC. Genome-wide molecular target search and luciferase reporter assays showed that prothymosin-α (PTMA) and purine nucleoside phosphorylase (PNP) are directly regulated by miR-1 and miR-133a. Silencing of these two genes significantly inhibited cell proliferation and invasion, and increased apoptosis in BC cells. Immunohistochemistry showed that PTMA expression levels were significantly higher in BC compared to normal bladder epitheliums. PTMA and PNP were identified as new target genes regulated by the miR-1 and miR-133a cluster in BC. These genes may function as oncogenes contributing to cell proliferation and invasion in BC. Tumor suppressive miR-1 and miR-133a-mediated novel molecular targets may provide new insights into the potential mechanisms of BC oncogenesis.

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