Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, NY 14642, USA.
James P. Wilmot Cancer Institute, University of Rochester Medical Center, Rochester, NY 14642, USA.
Int J Mol Sci. 2023 Sep 6;24(18):13733. doi: 10.3390/ijms241813733.
The precise molecular mechanisms responsible for resistance to cisplatin-based chemotherapy in patients with bladder cancer remain elusive, while we have indicated that androgen receptor (AR) activity in urothelial cancer is associated with its sensitivity. Our DNA microarray analysis in control vs. AR-knockdown bladder cancer sublines suggested that the expression of a GABA B receptor GABBR2 and AR was correlated. The present study aimed to determine the functional role of GABBR2 in modulating cisplatin sensitivity in bladder cancer. AR knockdown and dihydrotestosterone treatment considerably reduced and induced, respectively, GABBR2 expression, and the effect of dihydrotestosterone was at least partially restored by an antiandrogen hydroxyflutamide. A chromatin immunoprecipitation assay further revealed the binding of AR to the promoter region of in bladder cancer cells. Meanwhile, expression was significantly elevated in a cisplatin-resistant bladder cancer subline, compared with control cells. In AR-positive bladder cancer cells, knockdown of GABBR2 or treatment with a selective GABA B receptor antagonist, CGP46381, considerably enhanced the cytotoxic activity of cisplatin. However, no additional effect of CGP46381 on cisplatin-induced growth suppression was seen in GABBR2-knockdown cells. Moreover, in the absence of cisplatin, CGP46381 treatment and GABBR2 knockdown showed no significant changes in cell proliferation or migration. These findings suggest that GABBR2 represents a key downstream effector of AR signaling in inducing resistance to cisplatin treatment. Accordingly, inhibition of GABBR2 has the potential of being a means of chemosensitization, especially in patients with AR/GABBR2-positive bladder cancer.
导致膀胱癌患者对顺铂为基础的化疗产生耐药的确切分子机制仍难以捉摸，而我们已经表明，在尿路上皮癌中，雄激素受体（AR）的活性与其敏感性相关。我们在对照与 AR 敲低的膀胱癌亚系中的 DNA 微阵列分析表明，GABA B 受体 GABBR2 和 AR 的表达呈正相关。本研究旨在确定 GABBR2 在调节膀胱癌对顺铂敏感性中的功能作用。AR 敲低和二氢睾酮处理分别显著降低和诱导 GABBR2 的表达，而抗雄激素氟他胺至少部分恢复了二氢睾酮的作用。染色质免疫沉淀分析进一步显示 AR 与膀胱癌细胞中 GABBR2 的启动子区域结合。同时，与对照细胞相比，在顺铂耐药的膀胱癌亚系中，GABBR2 的表达显著升高。在 AR 阳性的膀胱癌细胞中，GABBR2 的敲低或用选择性 GABA B 受体拮抗剂 CGP46381 处理，显著增强了顺铂的细胞毒性活性。然而，在 GABBR2 敲低的细胞中，CGP46381 对顺铂诱导的生长抑制没有额外的作用。此外，在没有顺铂的情况下，CGP46381 处理和 GABBR2 敲低对细胞增殖或迁移没有显著影响。这些发现表明，GABBR2 是 AR 信号诱导顺铂耐药的关键下游效应因子。因此，抑制 GABBR2 有可能成为化疗增敏的一种手段，特别是在 AR/GABBR2 阳性的膀胱癌患者中。
