MicroRNAs (miRNAs) are short (≈22-nt) non-coding RNA molecules implicated in both development and disease that act by repressing translation or by inducing the cleavage of target RNA transcripts. Emerging evidence suggests that the altered regulation of miRNA may be involved in the pathogenesis of cancer. Here, we investigated the expression of the miRNA gene miR-221 by real-time PCR in human glioma tissues of varying grades of malignancy. The expression level of miR-221 was found to increase with glioma malignancy, whereas protein levels of a putative target, the cell cycle inhibitor and tumor suppressor gene p27Kip1, decreased. Using a luciferase reporter assay, we further confirmed the translational repression activity of miR-221 on p27 by identifying the target recognition element within the 3'UTR of p27. Our results suggest that miR-221 is a regulator of the tumor suppressor gene p27, and that its increased expression in advanced gliomas might contribute to glioma cell proliferation by a mechanism involving the repression of p27.

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