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Histone deacetylase inhibitors upregulate plakoglobin expression in bladder carcinoma cells and display antineoplastic activity in vitro and in vivo

Histone deacetylase inhibitors (HDACis) are emerging as a promising new class of anticancer agents displaying growth‐inhibitory activity and low toxicity in vivo. In this study, we examined the effect of sodium butyrate (NaB) and trichostatin A (TSA) on the growth of human bladder carcinoma cell lines in culture and TSA on the growth of EJ and UM‐UC‐3 human bladder xenografts in nude mice. NaB and TSA suppressed the growth of bladder cell lines at millimolar (1.5–4.3 mM) and micromolar (0.03–0.33 μM) concentrations, respectively, inducing concentration‐dependent cell death. Bladder carcinoma cells within the experimental panel displayed the phenotype of late‐stage bladder lesions expressing N‐cadherin in the absence of E‐cadherin accompanied by low levels of plakoglobin expression. Exposure of these cells to HDACis resulted in upregulation of plakoglobin with no change in E‐cadherin expression. A 2‐hr exposure to TSA was the minimal time required to upregulate plakoglobin in cells with downregulation to baseline levels occurring within 24 hr following drug removal. In mice bearing EJ and UM‐UC‐3 bladder xenografts, TSA (500 μg/kg/day) caused suppression of tumor growth compared with mice receiving vehicle alone. A > 70% reduction in mean final tumor volume was recorded in both bladder xenograft models with no detectable toxicity. The results suggest that TSA inhibits bladder carcinoma cell growth and may be a useful, relatively nontoxic agent for consideration in the treatment of late‐stage bladder tumors. © 2004 Wiley‐Liss, Inc.