Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, AL 36604, USA.
Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
Br J Cancer. 2014 Apr 15;110(8):2000-10. doi: 10.1038/bjc.2014.141. Epub 2014 Mar 18.
Emergence of castration-resistance in prostate cancer (PCa) is invariably associated with aggressive and metastatic disease. Previously, we reported promotion of castration-resistance upon downregulation of PPP2CA (encoding catalytic subunit of protein phosphatase 2A (PP2A), α-isoform); however, its role in PCa growth and metastasis remained undetermined.
PPP2CA was overexpressed/silenced in PCa cells by stable transfection. Gene expression was examined by reverse transcription polymerase chain reaction, immunoblot and immunofluorescence analyses, and transcriptional activity measured by luciferase-based promoter-reporter assay. Effect on PCa phenotype was studied in vitro and in orthotopic mouse model, and immunohistochemical/histological analyses performed to assess proliferation/apoptosis and confirm metastatic lesions.
An inverse association of PPP2CA expression was observed with epithelial-to-mesenchymal transition (EMT) and aggressive PCa phenotype. PPP2CA restoration resulted in decreased nuclear accumulation and transcriptional activity of β-catenin/NF-κB, and restitution of their activity abrogated PPP2CA-induced EMT reversal and suppression of PCa invasiveness. Akt mediated PPP2CA loss-induced nuclear accumulation of β-catenin/NF-κB through inactivation of Gsk3-β and IκB-α, respectively. Animal studies revealed a suppressive effect of PPP2CA expression on PCa growth and metastasis.
Our findings suggest that PPP2CA downregulation serves as a molecular link between gain of castration-resistance and aggressive PCa phenotype, and its restoration could be an effective preventive/therapeutic approach against the advanced disease.
前列腺癌（PCa）出现去势抵抗时，通常与侵袭性和转移性疾病有关。先前，我们报道了 PPP2CA（编码蛋白磷酸酶 2A（PP2A）的催化亚基，α 同工型）下调促进去势抵抗；然而，其在 PCa 生长和转移中的作用仍未确定。
通过稳定转染在 PCa 细胞中过表达/沉默 PPP2CA。通过逆转录聚合酶链反应、免疫印迹和免疫荧光分析检查基因表达，并通过基于荧光素酶的启动子报告测定测量转录活性。在体外和原位小鼠模型中研究对 PCa 表型的影响，并进行免疫组织化学/组织学分析以评估增殖/凋亡并确认转移病变。
观察到 PPP2CA 表达与上皮间质转化（EMT）和侵袭性 PCa 表型呈负相关。PPP2CA 的恢复导致β-catenin/NF-κB 的核积累和转录活性降低，并且它们的活性恢复消除了 PPP2CA 诱导的 EMT 逆转和抑制 PCa 侵袭性。Akt 通过分别使 Gsk3-β 和 IκB-α失活来介导 PPP2CA 缺失诱导的β-catenin/NF-κB 的核积累。动物研究显示 PPP2CA 表达对 PCa 生长和转移具有抑制作用。
我们的研究结果表明，PPP2CA 的下调是获得去势抵抗和侵袭性 PCa 表型之间的分子联系，其恢复可能是针对晚期疾病的有效预防/治疗方法。
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