Objective Recent studies demonstrated that circulating tumor cells (CTCs) contribute to the metastasis of prostate cancer. of E-cadherin was significantly increased, suggesting survivin plays an important role in EMT of CTCs. In addition, survivin siRNA significantly inhibited the invasiveness of CTCs and DU145 cells. Conclusions Survivin plays an important role in EMT of CTCs in prostate cancer, which might mediate the metastasis and invasion of prostate cancer. Keywords: circulating tumor cells, survivin, epithelial-mesenchymal transition, prostate cancer, diagnosis, metastasis Introduction Prostate cancer is one of the most common malignant tumors in men, and circulating tumor cells (CTCs) play key roles in its recurrence and metastasis.1C3 In recent years, the detection of CTCs has been used to monitor the recurrence and metastasis of prostate cancer.4C6 CTCs refers to tumor cells circulating in peripheral blood because of the spontaneous shedding of the primary tumor or shedding occurring during treatment. It is currently clear that CTCs represent the main cause of tumor metastasis.7 Epithelial tumor cells are transformed into cells with a mesenchymal phenotype via a biological process termed epithelial-mesenchymal transition (EMT), which eliminates cell polarity (4-Acetamidocyclohexyl) nitrate and the connection with the basement membrane and grants cells migratory, invasive, and anti-apoptosis activity and the ability to degrade extracellular matrix.8,9 Prior studies indicated that EMT is associated with wound healing, fibrosis, and tumor progression.8,10 Although only a handful of CTCs entering the circulatory system survive and further develop into metastatic foci, this is a critical process for achieving tumor metastasis.11,12 Metastatic prostate cancer is the final stage of prostate cancer progression. The optimal clinical treatment of metastatic prostate cancer remains controversial.13 Radiotherapy and chemotherapy can (4-Acetamidocyclohexyl) nitrate prolong the survival (4-Acetamidocyclohexyl) nitrate time of patients with metastatic prostate cancer, but the side effects of chemotherapy significantly reduce patients quality of life. Consequently, an in-depth knowledge of the system of prostate tumor metastasis and early testing of prostate tumor are the most significant task for analysis and treatment. Although CTCs had been discovered a lot more than a century ago, the precise mechanisms and role of the cells along the way of tumor metastasis stay unclear.14,15 CTCs may stand for a specific kind of cancer stem cell that stocks a number of the characteristics of stem cells, producing them more invasive.16 Aceto et?al. investigated the part of CTCs in prostate and breasts cancers, discovering that CTCs can raise the metastatic potential of tumor cells and play (4-Acetamidocyclohexyl) nitrate an integral part in tumor metastasis.17 Prior study indicated how the discussion between CTCs and platelets accelerates the pace of CTC metastasis. Labelle et?al.18 demonstrated that the interaction between platelet-derived TGF- and CTCs activates CTCs TGF-/Smad and NF-B signaling pathways, making tumor cells more aggressive via EMT. Survivin knockout suppresses ovarian metastatic tumors.19 Survivin is also involved in the radioresistance and castration resistance of prostate cancer.20,21 It was demonstrated that survivin levels of CTCs are associated with prostate cancer metastasis. Therefore, we examined whether survivin is involved in EMT in CTCs. Materials and methods Patients and samples In total, 100 patients with prostate tumor had been enrolled after offering written educated consent. The analysis was authorized by the ethics committee of Shandong Tumor Hospital (SHEC89E). All biopsy specimens from individuals with prostate tumor were examined simply by two experienced pathologists independently. Finally, peripheral bloodstream was collected from the patients, after which circulating tumor cells were collected as previously described.1,22 In brief, CTCs were isolated as EpCAM+/CD45? cells via FACS sorting on a MoFlo XDP high-speed cell sorter system (Beckman Coulter, Brea, CA, USA). The CTCs were identified via immunostaining of prostate-specific antigen (PSA). DU145 cells were obtained from American Type Culture Collection (Manassas, VA, USA). Immunofluorescence staining Cells isolated or transfected Plxna1 after 24 hours were quickly washed once with PBS, fixed with 2% PFA, and blocked with 2% goat serum. Cells were then stained with anti-PSA, anti-Twist, anti-E-cadherin, anti-vimentin, or anti-survivin antibody (1:100, Santa Cruz Biotechnology, Santa Cruz, CA, USA) overnight and then visualized via incubation with AF488 or AF594 secondary antibody for 1 hour at room temperature. Cells were imaged using an LSM 510 confocal microscope (Zeiss, Oberkochen, Germany) as described previously.23 Survivin siRNA transfection Survivin siRNA was synthesized as previously described.24 Survivin siRNA was transfected into CTCs or DU145 cells using the Neon Transfection (4-Acetamidocyclohexyl) nitrate System (Invitrogen, Thermo Fisher Scientific, Carlsbad, CA, USA) according to the manufacturers manual. The non-transfected cells were eliminated using G418. Cell.