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Cytokine therapies show promise in treating renal cell carcinoma (RCC). Transforming growth factor beta 1 (TGF-β1) is a cytokine whose downstream Smad2/3 signaling activity is inhibited by the protein phosphatase Mg2+/Mn2+-dependent 1 A (PPM1A). Here, we hypothesized that PPM1A may be involved in suppressing RCC cell aggressiveness through its negative regulation of Smad2/3. We quantified PPM1A expression from RCC tumors and matching healthy tissue and performed a Kaplan-Meier survival analysis. In silico analysis on PPM1A was performed using Cancer Genome Atlas-Kidney Renal Clear Cell Carcinoma and Clinical Proteomic Tumor Analysis Consortium RCC cohort data. We tested four RCC cell lines and selected the ACNH and A498 cells lines as expressing the greatest PPM1A levels. We assayed the effects of RNAi-mediated PPM1A silencing on invasiveness, proliferation, colony formation, and Smad2/3 phosphorylation in untreated and TGF-β1-stimulated ACNH and A498 cells. A nude mouse A498 xenograft tumor model was constructed to validate PPM1A's effects in vivo. PPM1A levels are reduced in RCC tumors and are negatively correlated with RCC grade and stage. Below-median PPM1A expression is associated with reduced overall survival in RCC patients. PPM1A silencing promoted cellular invasiveness, proliferation, colony formation, and Smad2/3 phosphorylation under TGF-β1-stimulated conditions but not under untreated conditions. These effects of PPM1A were shown to be dependent on Smad2/3. Intratumor PPM1A overexpression inhibited A498 xenograft tumor growth. This study establishes a direct link between PPM1A's suppression of Smad2/3 signaling and RCC cell aggressiveness. PPM1A could potentially serve as a biomarker for RCC cell aggressiveness. [ABSTRACT FROM AUTHOR]

Background: Clear cell renal cell carcinoma (ccRCC), as the commonest type among renal cell cancers, is featured with easy relapse and metastasis. Despite mounting achievements on its treatment and diagnosis, the identification of new biomarkers remains urgent. Purposes: Present study aimed to explore the role of microRNA-4429 (miR-4429) in ccRCC. Methods: The expression of miR-4429 and cyclin-dependent kinase 6 (CDK6) was evaluated by real-time polymerase chain reaction and Western blot. Cell proliferation, migration and invasion was evaluated by MTT and transwell assays. The interaction between miR-4429 and CDK6 was assessed by luciferase reporter assay. Prognostic significance of miR-4429 was evaluated by Kaplan-Meier analysis. Correlation between miR-4429 and CDK6 was determined by Spearman's correlation analysis. Results: Firstly, the downregulation of miR-4429 and upregulation of CDK6 in ccRCC tissues and cells were uncovered by quantitative real-time polymerase chain reaction. The prognostic significance of miR-4429 in ccRCC patients was proved by Kaplan-Meier analysis. Gain- and loss-of-function assays validated the suppressive effect of miR-4429 on cell proliferation, migration, invasion, as well as epithelial-mesenchymal transition (EMT) progression. The interaction between miR-4429 and CDK6 was predicted by bioinformatics tool and confirmed by luciferase reporter assay. And the negative expression correlation between miR-4429 and CDK6 was verified by Spearman's correlation analysis. Rescue assays confirmed the role of miR-4429/CDK6 in proliferation, metastasis and EMT progression in ccRCC. Conclusions: Present study revealed that miR-4429 suppressed ccRCC tumor progression and EMT by targeting CDK6. [ABSTRACT FROM AUTHOR]