Bera Amit, Ghosh-Choudhury Nandini, Dey Nirmalya, Das Falguni, Kasinath Balakuntalam S, Abboud Hanna E, Choudhury Goutam Ghosh
Department of Medicine, University of Texas Health Science Center at San Antonio, TX, United States.
Cell Signal. 2013 Dec;25(12):2575-86. doi: 10.1016/j.cellsig.2013.08.005. Epub 2013 Aug 24.
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 miR-21 regulates renal cancer cell proliferation is poorly understood. Addiction to constitutive NFκB 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 NFκB, IKKβ and IκB, which results in attenuation of NFκB 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, IKKβ, IκB and NFκB 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/IKKβ/IκB phosphorylation and NFκB transcriptional activity. Furthermore, IKKβ and p65 were required for miR-21-induced renal cancer cell proliferation. Interestingly, miR-21 controlled the expression of cyclin D1 through NFκB-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/IKKβ and NFκB-dependent cyclin D1 expression for renal carcinoma cell proliferation by increased miR-21 levels.
微小RNA在包括肾细胞癌在内的许多肿瘤中调节转录后水平的格局。我们最近发现肾肿瘤中miR-21的表达显著增加，并且这种微小RNA在体外促进肾癌细胞的增殖。然而，miR-21调节肾癌细胞增殖的机制仍知之甚少。依赖组成型NFκB活性是包括肾癌在内的许多癌症的标志。通过在肾癌细胞中使用miR-21海绵来阻断miR-21的内源性功能，我们发现NFκB的p65亚基、IKKβ和IκB的磷酸化受到抑制，这导致NFκB转录活性减弱。肿瘤抑制因子PTEN的轻微减少与多种恶性肿瘤有关。我们之前表明miR-21在肾癌细胞中靶向PTEN。用小干扰RNA抑制PTEN可恢复miR-21海绵诱导的p65、IKKβ、IκB磷酸化抑制和NFκB转录活性，同时逆转miR-21海绵降低的Akt磷酸化。组成型活性Akt的表达可防止miR-21海绵和PTEN介导的p65/IKKβ/IκB磷酸化和NFκB转录活性降低。此外，IKKβ和p65是miR-21诱导肾癌细胞增殖所必需的。有趣的是，miR-21通过NFκB依赖性转录控制细胞周期蛋白D1的表达。最后，我们证明miR-21调节的肾癌细胞增殖是由细胞周期蛋白D1和CDK4介导的。总之，我们的结果建立了一种磷酸酶-激酶偶联的分子顺序，涉及PTEN/Akt/IKKβ和NFκB依赖性细胞周期蛋白D1表达，通过增加miR-21水平来促进肾癌细胞增殖。
