MP62-19 AKR1C3 OVEREXPRESSION IN PROSTATE CANCER PROMOTES EPITHELIAL-MESENCHYMAL TRANSITION AND METASTASIS VIA ACTIVATION OF MAPK/ERK SIGNALING AND UPREGULATION OF ZEB1 Bin Wang, Kaijie Wu*, Jun Huang, Xi’an, China, People’s Republic of; Jer-Tsong Hsieh, Dallas, TX; Dalin He, Xi’an, China, People’s Republic of INTRODUCTION AND OBJECTIVES: AKR1C3, as a crucial steroidogenic enzyme, facilitated intratumoral androgen biosynthesis and androgen receptor (AR) reactivation in the development of castration-resistant prostate cancer. Also, amount of data have shown that AKR1C3 expression was significantly elevated in clinical metastatic prostate cancer (PCa) specimens, indicating an alternative role of AKR1C3 in PCa metastasis. Epithelial-mesenchymal transition (EMT) has been recognized to play pivotal roles in promoting carcinoma in- vasion and metastasis; however, the roles of AKR1C3 in EMT and PCa metastasis have not been fully elucidated. METHODS: C4-2, 22RV1-T and PC-3 cells with higher AKR1C3 expression were selected and treated with several specific AKR1C3 shRNAs or small molecule inhibitor, and the cell migration and invasion abilities were detected by wound healing assay and Transwell assay. The expression of EMT markers (i.e., E-cadherin and vimentin) and the related transcription factors (i.e., Snail, Slug, ZEB1 and Twist1) was examined by Western blot or quantitative PCR assays, and the phosphorylation of AKT or ERK was detected by Western blot. Also, the expression of vimentin, ZEB1 and p-ERK (T202/Y204) was detected by immunohistochemical staining in PC-3 xenograft tissues after AKR1C3 inhibitor treatment. The correlation between AKR1C3 and EMT markers (including EMT-related transcription factors) expression in clinical specimens from tissue microarray or TCGA database was analyzed. RESULTS: AKR1C3 was overexpressed in more aggressive PCa cell lines regardless of the AR status. Knock-down of AKR1C3 expression or inhibition of AKR1C3 activity could significantly sup- pressed cell migration and invasion abilities in vitro. Also, knock-down of AKR1C3 expression or inhibition of AKR1C3 activity could increase E-cadherin expression but decrease vimentin expression, in which the phosphorylation of ERK and the transcription factor ZEB1 expression were specifically downregulated. In consistency, inhibition of AKR1C3 activity by inhibitor treatment could decrease the expression of vimen- tin, ZEB1 and p-ERK (T202/Y204) in xenograft tissues in vivo. More- over, there was a significant correlation between AKR1C3 and EMT markers (i.e., E-cadherin, vimentin and ZEB1) in human PCa specimens. CONCLUSIONS: AKR1C3 is a novel EMT regulator in PCa metastasis through activation of MAPK/ERK signaling and upregulation of ZEB1 expression. Source of Funding: Grants from the National Natural Science Foundation of China (NSFC 81202014 to KW) and the Fundamental Research Funds for the Central Universities in China (to KW). MP62-20 CROSSTALK BETWEEN EPITHELIAL-MESENCHYMAL TRANSITION AND CASTRATION RESISTANCE IN PROSTATE CANCER Masaki Shiota*, Momoe Itsumi, Ario Takeuchi, Kenjiro Imada, Akira Yokomizo, Fukuoka, Japan; Hidetoshi Kuruma, Tokyo, Japan; Junichi Inokuchi, Katsunori Tatsugami, Takeshi Uchiumi, Yoshinao Oda, Seiji Naito, Masatoshi Eto, Fukuoka, Japan INTRODUCTION AND OBJECTIVES: Invasive and metastatic progression via the epithelial-mesenchymal transition (EMT) and acquisition of castration resistance are both critical steps in prostate cancer. However, the molecular mechanism of this interaction remains unclear. In this study, we aimed to elucidate the interaction of signaling between EMT and castration resistance, and to apply to the develop- ment of a novel therapeutic concept using transforming growth factor-ß (TGF-ß) inhibitor SB525334 combined with androgen-deprivation ther- apy against prostate cancer. METHODS: LNCaP and 22Rv1 cells were utilized. Gene and protein expression levels were evaluated by quantitative real-time po- lymerase chain reaction and Western blot analysis, respectively. Pro- tein expression in tissues was evaluated by immunohistochemistry. Cell invasion ability was examined by matrigel-invasion assay. 22Rv1 xenograft model in nude mice was utilized to investigate in vivo anti- tumor effect. RESULTS: The results showed that TGF-ß induced full-length and variant androgen receptor (AR) expression. In addition, highly invasive clone showed augmented full-length and variant AR expres- sion as well as acquisition of castration resistance. Conversely, full- length and variant AR as well as Twist1 and mesenchymal molecules expression were up-regulated in castration-resistant tumors (Fig. A). Actually, both full-length and variant AR expression were elevated in pT3 prostate cancer tissue, compared with pT2 tissues (Fig. B). Finally, TGF-ß inhibitor suppressed Twist1 and AR expression as well as prostate cancer growth combined with castration (Fig. C). CONCLUSIONS: Taken together, these results demonstrated that Twist1/AR signaling was augmented in castration-resistant as well as mesenchymal-phenotype prostate cancer, suggesting mutual and functional crosstalk between EMT and castration resistance, which may play a crucial role in prostate cancer progression. In addition, inhibiting EMT may contribute to sustain castration sensitivity in prostate cancer. Source of Funding: Kakenhi grants (25462483, 25462484 and 26861273) from the Ministry of Education, Culture, Sports, e820 THE JOURNAL OF UROLOGY â Vol. 195, No. 4S, Supplement, Monday, May 9, 2016