NFκB-mediated cyclin D1 expression by microRNA-21 influences renal cancer cell proliferation

MicroRNAs regulate post-transcriptomic landscape in many tumors including renal cell carcinoma. We have recently shown significantly increased expression of miR-21 in renal tumors and that this miRNA contributes to the proliferation of renal cancer cells in culture. However, the mechanism by which nniR-21 regulates renal cancer cell proliferation is poorly understood. Addiction to constitutive NF kappa B activity is hallmark of many cancers including renal cancer. Using miR-21 Sponge in renal cancer cells to block endogenous function of miR-21, we show inhibition of phosphorylation of p65 subunit of NF kappa B, IKK beta and I kappa B, which results in attenuation of NF kappa B transcriptional activity. Subtle reduction in the tumor suppressor PTEN has been linked to various malignancies. We showed previously that miR-21 targeted PTEN in renal cancer cells. Inhibition of PTEN by siRNAs restored miR-21 Sponge-induced suppression of phosphorylation of p65, IKK beta, I kappa B and NF kappa B transcriptional activity along with reversal of miR-21 Sponge-reduced phosphorylation of Akt. Expression of constitutively active Akt protected against miR-21 Sponge- and PTEN-mediated decrease in p65/IKK beta/I kappa B phosphorylation and NF kappa B transcriptional activity. Furthermore, IKK beta and p65 were required for miR-21-induced renal cancer cell proliferation. Interestingly, miR-21 controlled the expression of cyclin D1 through NF kappa B-dependent transcription. Finally, we demonstrate that miR-21-regulated renal cancer cell proliferation is mediated by cyclin D1 and CDK4. Together, our results establish a molecular order of a phosphatase-kinase couple involving PTEN/Akt/IKK beta and NF kappa B-dependent cyclin D1 expression for renal carcinoma cell proliferation by increased miR-21 levels. (C)0 2013 Elsevier Inc. All rights reserved.