BACKGROUND 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. METHODS 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. RESULTS 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. CONCLUSIONS 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.

中文翻译：

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PPM1A 通过抑制 Smad2/3 信号传导抑制 RCC 细胞的增殖和侵袭


背景细胞因子疗法在治疗肾细胞癌(RCC)方面显示出前景。转化生长因子 β 1 (TGF-β1) 是一种细胞因子，其下游 Smad2/3 信号传导活性受到蛋白磷酸酶 Mg2+/Mn2+ 依赖性 1 A (PPM1A) 的抑制。在这里，我们假设 PPM1A 可能通过其对 Smad2/3 的负调节参与抑制 RCC 细胞的侵袭性。方法 我们定量了 RCC 肿瘤和匹配健康组织的 PPM1A 表达，并进行了 Kaplan-Meier 生存分析。使用癌症基因组图谱-肾透明细胞癌和临床蛋白质组肿瘤分析联盟 RCC 队列数据对 PPM1A 进行计算机分析。我们测试了四种 RCC 细胞系，并选择 ACNH 和 A498 细胞系表达最高的 PPM1A 水平。我们检测了 RNAi 介导的 PPM1A 沉默对未经处理和 TGF-β1 刺激的 ACNH 和 A498 细胞的侵袭性、增殖、集落形成和 Smad2/3 磷酸化的影响。构建裸鼠A498异种移植肿瘤模型以验证PPM1A的体内作用。结果 RCC 肿瘤中 PPM1A 水平降低，且与 RCC 分级和分期呈负相关。 PPM1A 表达低于中值与 RCC 患者总生存期降低相关。在 TGF-β1 刺激的条件下，PPM1A 沉默促进细胞侵袭、增殖、集落形成和 Smad2/3 磷酸化，但在未处理的条件下则不然。 PPM1A 的这些作用被证明依赖于 Smad2/3。肿瘤内 PPM1A 过表达抑制 A498 异种移植肿瘤生长。结论 这项研究确立了 PPM1A 对 Smad2/3 信号传导的抑制与 RCC 细胞侵袭性之间的直接联系。 PPM1A 有可能作为 RCC 细胞侵袭性的生物标志物。