Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
James Buchanan Brady Urological Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Endocr Relat Cancer. 2020 Apr;27(4):231-244. doi: 10.1530/ERC-20-0004.
Androgen receptor (AR) and estrogen receptor-β (ERβ) have been implicated in urothelial tumor outgrowth as promoters, while underlying mechanisms remain poorly understood. Our transcription factor profiling previously performed identified FOXO1 as a potential downstream target of AR in bladder cancer cells. We here investigated the functional role of FOXO1 in the development and progression of urothelial cancer in relation to AR and ERβ signals. In non-neoplastic urothelial SVHUC cells or bladder cancer lines, AR/ERβ expression or dihydrotestosterone/estradiol treatment reduced the expression levels of FOXO1 gene and induced those of a phosphorylated inactive form of FOXO1 (p-FOXO1). In chemical carcinogen-induced models, FOXO1 knockdown via shRNA or inhibitor treatment resulted in considerable induction of the neoplastic transformation of urothelial cells or bladder cancer development in mice. Similarly, FOXO1 inhibition considerably induced the viability, migration, and invasion of bladder cancer cells. Importantly, in FOXO1 knockdown sublines, an anti-androgen hydroxyflutamide or an anti-estrogen tamoxifen did not significantly inhibit the neoplastic transformation of urothelial cells, while dihydrotestosterone or estradiol did not significantly promote the proliferation or migration of urothelial cancer cells. In addition, immunohistochemistry in surgical specimens showed that FOXO1 and p-FOXO1 expression was down-regulated and up-regulated, respectively, in bladder tumor tissues, which was further associated with worse patient outcomes. AR or ERβ activation is thus found to correlate with inactivation of FOXO1 which appears to be their key downstream effector. Moreover, FOXO1, as a tumor suppressor, is likely inactivated in bladder cancer, which contributes in turn to inducing urothelial carcinogenesis and cancer growth.
雄激素受体 (AR) 和雌激素受体-β (ERβ) 已被认为是促进尿路上皮肿瘤生长的促进剂，但其潜在机制仍知之甚少。我们之前进行的转录因子谱分析确定 FOXO1 是膀胱癌细胞中 AR 的潜在下游靶标。我们在此研究了 FOXO1 在与 AR 和 ERβ 信号相关的尿路上皮癌发生和进展中的功能作用。在非肿瘤性尿路上皮 SVHUC 细胞或膀胱癌系中，AR/ERβ 表达或二氢睾酮/雌二醇处理降低了 FOXO1 基因的表达水平，并诱导了 FOXO1 的磷酸化失活形式 (p-FOXO1) 的表达。在化学致癌剂诱导的模型中，通过 shRNA 或抑制剂处理敲低 FOXO1 导致尿路上皮细胞的肿瘤转化或小鼠膀胱癌的发展得到相当大的诱导。同样，FOXO1 抑制也显著诱导了膀胱癌细胞的活力、迁移和侵袭。重要的是，在 FOXO1 敲低亚系中，抗雄激素羟基氟他胺或抗雌激素他莫昔芬不能显著抑制尿路上皮细胞的肿瘤转化，而二氢睾酮或雌二醇不能显著促进尿路上皮癌细胞的增殖或迁移。此外，手术标本的免疫组织化学显示，FOXO1 和 p-FOXO1 的表达在膀胱肿瘤组织中分别下调和上调，这与患者预后较差进一步相关。因此，AR 或 ERβ 的激活与 FOXO1 的失活相关，FOXO1 似乎是它们的关键下游效应物。此外，作为肿瘤抑制因子的 FOXO1 可能在膀胱癌中失活，这反过来又有助于诱导尿路上皮癌发生和肿瘤生长。
