The Role of the Androgen Receptor in the Development and Progression of Bladder Cancer
Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, 601 Elmwood Avenue, Box 626, Rochester, NY 14642, USA. Japanese Journal of Clinical Oncology
(Impact Factor: 2.02).
05/2012; 42(7):569-77. DOI: 10.1093/jjco/hys072
Men are at a higher risk of developing bladder cancer than women. Since bladder cancer cell lines and tissues were found to express the androgen receptor, efforts have been made to inspect whether androgen-mediated androgen receptor signals are implicated in bladder carcinogenesis as well as cancer progression. Mounting evidence supports the view that bladder cancer is a member of the endocrine-related tumors and may clearly explain the gender-specific difference in the incidence. However, the underlying mechanisms of how androgen receptor signals regulate bladder cancer growth are still far from fully characterized. Moreover, it remains controversial whether the androgen receptor pathway always plays a dominant role in bladder cancer progression. In this review, we summarize the available data on the involvement of androgen receptor signaling in bladder cancer. In particular, current evidence demonstrating the stimulatory effects of androgens on tumor progression or, more convincingly, tumorigenesis via the androgen receptor pathway may offer great potential for androgen deprivation as a therapeutic or chemopreventive option in patients with bladder cancer.
Available from: Helene Thygesen
- "The basis for the gender-related difference in incidence has not been precisely ascertained. Expression of the androgen receptor has been suggested to play a role not only in the development of the higher incidence of bladder cancer in males but also in determination of prognosis, although some conflicting results have been reported [reviewed in (19)]. It will be of interest to examine STAG2 mutation in relation to both gender and the status of androgen receptor and its targets. "
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ABSTRACT: Inactivating mutations of STAG2 have been reported at low frequency in several cancers. In glioblastoma, the function of STAG2 has been related to maintenance of euploidy via its role in the cohesin complex. In a screen of a large series of bladder tumors and cell lines, we found inactivating mutations (nonsense, frameshift and splicing) in 67 of 307 tumors (21.8%) and 6 of 47 cell lines. Thirteen missense mutations of unknown significance were also identified. Inactivating mutation was associated with low tumor stage (p=0.001) and low grade (p=0.0002). There was also a relationship with female patient gender (p=0.042). Examination of copy number profiles revealed an inverse relationship of mutation with both fraction of genome altered and with whole chromosome copy number changes. Immunohistochemistry showed that in the majority of cases with inactivating mutations, STAG2 protein expression was absent. Strikingly we identified a relatively large sub-set of tumors (12%) with areas of both positive and negative immunoreactivity, in only 4 of which a potentially function-altering mutation was detected. Regions of differential expression were contiguous and showed similar morphological phenotype in all cases. Microdissected positive and negative areas from one tumor showed an inactivating mutation to be present only in the negative area, suggesting intra-tumoral sub-clonal genomic evolution. Our findings indicate that loss of STAG2 function plays a more important role in non-invasive than in muscle-invasive bladder cancer and suggest that cohesin complex-independent functions are likely to be important in these cases.
Available from: Chinthalapally V Rao
- "It is important to note that CP-31398 showed dose-dependent suppression of invasive TCC inhibition in female mice, with the higher dose showing 100% inhibition of invasive TCC (Table W1). The mechanisms for the difference in SV40 T antigen–induced tumor progression in male versus female mice are not clear, but they may be due, in part, to the influence of sex hormones on tumor growth  . Epidemiological data indicate that men also have a three to four times higher chance of developing bladder cancer compared with women; however, differences between men and women in the rate of tumor progression have not been studied extensively. "
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ABSTRACT: The high prevalence of bladder cancer and its recurrence make it an important target for chemoprevention. About half of invasive urothelial tumors have mutations in p53. We determined the chemopreventive efficacy of a p53-stabilizing agent, CP-31398, in a transgenic UPII-SV40T mouse model of bladder transitional cell carcinoma (TCC) that strongly resembles human TCC. After genotyping, six-week-old UPII-SV40T mice (n = 30/group) were fed control (AIN-76A) or experimental diets containing 150 or 300 ppm of CP-31398 for 34 weeks. Progression of bladder cancer growth was monitored by magnetic resonance imaging. At 40 weeks of age, all mice were killed; urinary bladders were collected to determine weights, tumor incidence, and histopathology. There was a significant increase in bladder weights of transgenic versus wild-type mice (male: 140.2 mg vs 27.3 mg, P < .0001; female: 34.2 mg vs 14.8 mg, P < .0001). A significant decrease in the bladder tumor weights (by 68.6-80.2%, P < .0001 in males and by 36.9-55.3%, P < .0001 in females) was observed in CP-31398-treated mice. Invasive papillary TCC incidence was 100% in transgenic mice fed control diet. Both male and female mice exposed to CP-31398 showed inhibition of invasive TCC. CP-31398 (300 ppm) completely blocked invasion in female mice. Molecular analysis of the bladder tumors showed an increase in apoptosis markers (p53, p21, Bax, and Annexin V) with a decrease in vascular endothelial growth factor in transgenic mice fed CP-31398. These results suggest that p53-modulating agents can serve as potential chemopreventive agents for bladder TCC.
Available from: Koji Izumi
- "In the presence of androgens, the AR located in the cytoplasm dissociates from heat-shock protein and translocates to the nucleus, leading to regulation of the target genes. AR and other nuclear receptors have been detected in the urothelium and/or stromal cells of the urinary bladder, and emerging data suggest that bladder cancer is an endocrine-related neoplasm (reviewed in Li et al. (2012) and Miyamoto et al. (2012)). AR signals have been implicated in bladder carcinogenesis and tumor progression . "
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ABSTRACT: Androgen receptor (AR) signals have been implicated in bladder carcinogenesis and tumor progression. Activation of Wnt/β-catenin signaling has also been reported to correlate with bladder cancer progression and poor patients' outcomes. However, cross-talk between AR and β-catenin pathways in bladder cancer remains uncharacterized. In radical cystectomy specimens we immunohistochemically confirmed aberrant expression of β-catenin especially in aggressive tumors. There was a strong association between nuclear expressions of AR and β-catenin in bladder tumors (P=0.0215). Kaplan-Meier and log-rank tests further revealed that reduced membranous β-catenin expression (P=0.0276), nuclear β-catenin expression (P=0.0802), and co-expression of nuclear AR and β-catenin (P=0.0043) correlated with tumor progression after cystectomy. We then assessed the effects of androgen on β-catenin in AR-positive and AR-negative bladder cancer cell lines. A synthetic androgen R1881 increased the expression of an active form of β-catenin and its downstream target c-myc only in AR-positive lines. R1881 also enhanced the activity of β-catenin-mediated transcription, which was abolished by an AR antagonist hydroxyflutamide. Using western blotting and immunofluorescence, R1881 was found to induce nuclear translocation of β-catenin when co-localized with AR. Finally, co-immunoprecipitation revealed androgen-induced associations of AR with β-catenin or T cell factor (TCF) in bladder cancer cells. Thus, it was likely that androgen was able to activate β-catenin signaling through the AR pathway in bladder cancer cells. Our results also suggest that activation of β-catenin signaling possibly via formation of AR/β-catenin/TCF complex contributes to the progression of bladder cancer, which may enhance the feasibility of androgen deprivation as a potential therapeutic approach.
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