MP98-11 GPX2 IS A PROGNOSTIC MARKER AND HAS A THERAPEUTIC POTENTIAL VIA REGULATION OF OXIDATIVE STRESS IN BLADDER CANCER Taku Naiki*, Aya Naiki-Ito, Toshiki Etani, Keitaro Iida, Ryosuke Ando, Takashi Nagai, Noriyasu Kawai, Satoru Takahashi, Takahiro Yasui, Nagoya City, Japan INTRODUCTION AND OBJECTIVES: Reactive oxygen spe- cies (ROS) have been identified as important chemical mediators in cell growth and differentiation. The glutathione redox system is the main mechanism protecting against damage caused by ROS in the human body. In this study, we investigated the role and therapeutic potential of the glutathione redox system in bladder cancer. METHODS: The expression levels of glutathione peroxidase 2 (GPX2) and Ki-67 proteins were analyzed in human transurethral resection (TUR) specimens by immunohistochemistry; correlations be- tween the GPX2 expression and prognosis were also analyzed. In addition, male F344 rats were given 0.05% BBN in drinking water and 0.1% Phenyl isothiocyanate in their diet for 36 weeks. Bladder tissue samples were collected from each animal for analyses. Furthermore, the rat cell line, BC31, and human cell lines, T24, RT4, TCC-SUP, and 5637, were transfected with GPX2 siRNA and negative control siRNA (NC). Subsequently, cell proliferation rates and ROS levels were investigated by cell counting, DCFH assay, western blotting, and flow cytometry. siRNA- or NC- transfected BC31 cells were subcutaneously implanted into nude mice. RESULTS: GPX2 was strongly expressed in low grade and low MIB-1 index cancers. PFS and CSS rates were significantly better in patients with higher GPX2 than in those with lower GPX2. Furthermore, GPX2 expression was significantly lower in the normal epithelium of the control group of animals with bladder cancer when compared with those in the treated group, and GPX2 expression was significantly higher in urothelial cancer than in the normal epithelium. BC31 and RT4 cells strongly expressed GPX2 when compared with the other cell lines. Silencing of GPX2 caused significant growth inhibition, and the DCFH assay revealed significant reductions in ROS levels in the siRNA- treated cells. Caspase-dependent apoptosis was fund to be the cause for the decrease in proliferation rates in the siRNA group. Interestingly, tumor growth was significantly inhibited in the BC31-implanted nude mice using the siRNA strategy for Gpx2. CONCLUSIONS: Our findings demonstrated that GPX2 plays several important roles in carcinogenesis through the regulation of apoptosis against intracellular ROS, and may be considered as a novel marker or therapeutic target in bladder cancer. Source of Funding: none MP98-12 FOXA1 KNOCKOUT IS ASSOCIATED WITH INCREASED CARCINOGENIC SUSCEPTIBILITY AND ANDROGEN RECEPTOR EXPRESSION IN MURINE BLADDER CANCER Lauren Shuman*, Zongyu Zheng, Hironobu Yamashita, Joshua Warrick, Hershey, PA; Klaus Kaestner, Philadelphia, PA; David DeGraff, Hershey, PA INTRODUCTION AND OBJECTIVES: In the US, men are 3 to 4 times more likely to be diagnosed with bladder cancer (BC), however, women frequently present with more advanced disease and have inferior clinical outcomes. Recent data indicates androgen (AR) and estrogen receptors (ERa and ERb) play an important role in BC tumorigenesis and progression. These hormone receptors physically interact with transcription factor Forkhead box A1 (FOXA1), playing an important role in transcriptional activity of AR and ER. While the role for FOXA1/AR/ER complexes in BC is unknown, Foxa1 knockout (KO) results in sex-specific changes in murine urothelial differentiation. Interestingly, BC development in mice exposed to the carcinogen N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) also occurs in a sex- dependent manner. Therefore, we initiated a study to determine the impact of Foxa1 KO on sex-dependent development of BC in mice. METHODS: To determine the effect of Foxa1 KO on BC development in males and females, Foxa1 ablation was achieved using a tamoxifen-inducible ubiquitin Cre (UBC-CreERT2) system. Control and KO mice were then exposed to BBN for 16 weeks and bladders were harvested for H&E, immunohistochemistry (IHC), and qPCR. RESULTS: Following 16 weeks of BBN treatment, female control mice appeared relatively resistant to carcinogenesis compared to males, which exhibited pre-neoplastic changes including keratinizing squamous metaplasia. However, Foxa1 KO followed by BBN treatment resulted in development of keratinizing squamous metaplasia in fe- males and progression to muscle invasive BC in males. IHC for Krt14 and Ki67 confirmed the presence of squamous differentiation and increased proliferative index in both male and female Foxa1 KO mice treated with BBN. Interestingly, our analysis also shows that nuclear AR expression is increased in male control bladder tissue compared to female control bladder tissue. However, Foxa1 KO increases AR expression independent of sex. CONCLUSIONS: Overall, our data indicates that Foxa1 KO in adult male and female mice renders them more susceptible to carcin- ogen exposure. Interestingly, Foxa1 KO resulted in development of keratinizing squamous metaplasia in female mice. Additionally, AR was slightly increased in Foxa1 KO mice, independent of sex. These data indicate loss of FOXA1 in human BC may be associated with increased AR expression and activity, and subsequent disease progression. Future work includes determining ERa and ERb expression following Foxa1 KO, as well as the mechanism by which Foxa1 KO alters AR expression and activity in BC. Source of Funding: R00CA17212 MP98-13 HOTAIR AFFECTS BLADDER CANCER EPITHELIAL-TO-MESENCHYME TRANSITION THROUGH BOTH THE CANONICAL WNT-PATHWAY AND EXTRACELLULAR VESICLES Thomas Osinski*, Claudia Berrondo, Jonathan Flax, Samuel Richheimer, Rochester, NY; Victor Kucherov, Philidelphia, PA; Carla Beckham, Rochester, NY INTRODUCTION AND OBJECTIVES: Previously we identified the long non-coding RNA Hox antisense intergenic transcript (HOTAIR) enriched in urothelial bladder cancer (UBC) cell lines, extracellular vesicles (ECVs), patient tumors and urinary ECVs. Importantly, HOTAIR affects the expression of genes involved in epithelial-to- mesenchyme transition (EMT). Critically, we found reduced HOTAIR expression correlates with decreased in vitro migration and invasion. e1316 THE JOURNAL OF UROLOGY â Vol. 197, No. 4S, Supplement, Tuesday, May 16, 2017