Abstract: Objective　To investigate the role and mechanism of abnormal expression of Survivin in the metastasis of prostate cancer (PCa). Methods　(1) The difference of Survivin mRNA expression between normal prostate tissue and PCa tissue was analyzed by TCGA database, and the lymph node metastasis, Gleason grade and prognosis were analyzed. (2) Immunohistochemical staining was used to detect the expression of Survivin protein in 15 cases of benign prostatic hyperplasia (BPH) biopsies and 60 cases of PCa biopsies, and the differences of Survivin protein expressions were compared between different clinical features of the patients. (3) The expression levels of Survivin in routine culture of human benign prostatic hyperplasia cell line BPH and human PCa cell lines LNCaP, Du-145 and PC-3 were detected by Western blot  assay. LNCaP cells were used to construct Survivin stable overexpression group (Survivin-OE) and corresponding control group (Vector). At the same time, Survivin stable knockdown group (Survivin-KD) and corresponding control group (NC) were constructed in PC-3 cells. CCK-8 proliferation assay and Transwell assay were used to detect the changes of cell invasion and proliferation after knocking-down and overexpressing Survivin. Western blot assay was used to detect the expression of Survivin, E-cadherin, N-cadherin and proteins related to TGF-β/Smad pathway such as phosphorylated Smad2/3, TGF-β1 and Smad4 in two kinds of cells. Results　(1) The results of TCGA database analysis showed that Survivin was abnormally high in prostate adenocarcinoma, and the expression levels of Survivin were higher in patients with lymph node metastasis than those in patients without lymph node metastasis (P＜0.01). The expression levels of Survivin increased with the increase of Gleason score (P＜0.01), and the progression-free survival time was significantly shorter in PCa patients with high expression of Survivin than that of patients with low expression of Survivin (P＜0.01). (2) Immunohistochemistry confirmed that the high expression ratio of Survivin protein was significantly higher in PCa samples than that in BPH tissues (60.0% vs. 26.7%, χ2=5.357, P＜0.05). The proportion of high expression of Survivin was significantly increased in patients with clinical stage T3+T4, local lymph node metastasis and distant metastasis (P＜0.05). (3) In vitro experiment results showed that Survivin levels were higher in LNCaP, DU-145 and PC-3 cells than those in BPH (P＜0.05). The overexpression of Survivin increased the proliferation and invasion ability in LNCaP cells. The expression of epithelial marker E-cadherin decreased, the expression of interstitial marker N-cadherin increased, and the expression levels of pSmad2/3, TGF-β1 and Smad4 increased after overexpressing Survivin. However, the underexpression of Survivin decreased the proliferation and invasion ability in PC-3 cells. The expression of epithelial marker E-cadherin increased, the expression of interstitial marker N-cadherin decreased and the expression levels of pSmad2/3, TGF-β1 and Smad4 decreased after knocking-down Survivin. Conclusion　Survivin is abnormally highly expressed in prostate adenocarcinoma, which can promote EMT progress to improve tumor metastasis and invasion by regulating TGF-β/Smad pathway in prostate cancer.

Key words: prostatic neoplasms, neoplasm metastasis, transforming growth factor beta, Smad proteins, cadherins, epithelial-mesenchymal transition, survivin