br AR signaling and urothelial cancer

AR signaling and urothelial cancer progression As shown in other types of malignancies, such as prostate cancer cells, it has been documented that androgens induce AR expression and its nuclear translocation as well as ARE promoter activity in urothelial cancer cells (Chen et al., 2003, Izumi et al., 2012, Jing et al., 2014, Kawahara et al., 2015b, Kawahara et al., 2016, Li et al., 2013, Miyamoto et al., 2007, Overdevest et al., 2012, Shiota et al., 2012, Zheng et al., 2011). In some of these studies, AR antagonists, such as flutamide, bicalutamide, and enzalutamide, were shown to block the effects of androgens on AR expression or transactivation. Thus, androgens are able to activate the AR in urothelial cancer cells. In addition, non-androgenic compounds, such as EGF, were shown to increase AR transcriptional activity in 3466 cancer cells, which was restored by the anti-androgens (Izumi et al., 2012). Androgens have also been shown to stimulate urothelial cancer cell proliferation, migration, and/or invasion via the AR pathway (Ding et al., 2016, Izumi et al., 2012, Jing et al., 2014, Kameyama et al., 2017, Kawahara et al., 2015b, Kawahara et al., 2016, Miyamoto et al., 2007, Overdevest et al., 2012, Shiota et al., 2012, Zheng et al., 2011). EGF could also increase the viability of AR-positive bladder cancer cells in the absence of androgens (Hsieh et al., 2013, Izumi et al., 2012). Accordingly, anti-androgen treatment or AR knockdown in cells cultured in the presence of androgen resulted in their impaired growth (Ding et al., 2016, Izumi et al., 2012, Jing et al., 2014, Jitao et al., 2014, Kawahara et al., 2015b, Kawahara et al., 2016, Miyamoto et al., 2007, Overdevest et al., 2012, Shiota et al., 2012, Wu et al., 2010, Zheng et al., 2011). Animal studies using heterotopic or orthotopic xenograft models for bladder cancer have also demonstrated that castration or treatment with anti-AR compounds in male mice inhibits tumor growth (Jing et al., 2014, Jitao et al., 2014, Kawahara et al., 2016, Miyamoto et al., 2007, Shiota et al., 2012, Wu et al., 2010, Zheng et al., 2015). Furthermore, in a transgenic mouse model expressing SV40 large T antigen specifically in urothelium (via uroplakin II promoter) and spontaneously developing bladder cancer, orchiectomy after tumor formation retarded its growth, compared with control animals or castrated animals with DHT supplement (Johnson et al., 2008). In this uroplakin II-SV40T transgenic model, orchiectomy also reduced microvessel density in bladder tumors and increased the expression of an anti-angiogenic factor TSP-1 (Johnson et al., 2008), indicating that androgens promote angiogenesis in urothelial cancer. Recent studies have also identified a variety of molecules or pathways regulated by androgen-mediated AR signals in urothelial cancer cells. Those known to involve urothelial cancer cell proliferation/migration/invasion as well as angiogenesis/metastasis include β-catenin/Wnt signaling and its downstream targets c-myc/cyclin D1 (Li et al., 2013, Lin et al., 2013, Shiota et al., 2012, Wu et al., 2010), CD24 and its regulator GON4L (Agarwal et al., 2016, Ding et al., 2016, Overdevest et al., 2012), EGFR family and its downstream AKT/ERK (Izumi et al., 2012, Zheng et al., 2011), ELK1 (Kawahara et al., 2015a, Kawahara et al., 2015b), matrix metalloproteinases (MMPs) (Ding et al., 2016, Kawahara et al., 2016, Lin et al., 2013, Lin et al., 2015, Miyamoto et al., 2007, Wu et al., 2010), and vascular endothelial growth factor (VEGF) (Ding et al., 2016, Miyamoto et al., 2007). Interestingly, DHT and EGF appear to show synergistic effects on the proliferation as well as phosphorylation of EGFR, AKT, and ERK in bladder cancer cells (Izumi et al., 2012, Zheng et al., 2011). In addition, androgens were shown to induce epithelial-to-mesenchymal transition (EMT) in bladder cancer cells via modulating the expression of Slug as well as the activity of Wnt/β-catenin signaling (Jing et al., 2014, Jitao et al., 2014). More recent in vitro assays demonstrated that bladder cancer cells could recruit inflammatory/immune cells, including B cells (Ou et al., 2015), helper T cells (Tao et al., 2016), and neutrophils (Lin et al., 2015), leading to the induction of tumor cell invasion as well as the expression of AR and MMPs (e.g. MMP-1, MMP-2, MMP-13). These preclinical observations may thus represent underlying molecular mechanisms for the promoting effects of androgen-mediated AR signals on urothelial cancer progression.