Department of Pathology & Laboratory Medicine, University of Rochester Medical Center, Rochester, New York.
James P. Wilmot Cancer Institute, University of Rochester Medical Center, Rochester, New York.
Mol Cancer Ther. 2020 Sep;19(9):1930-1942. doi: 10.1158/1535-7163.MCT-20-0050. Epub 2020 Jul 31.
Although intravesical bacillus Calmette-Guérin (BCG) immunotherapy has been the gold standard for nonsurgical management of non-muscle-invasive bladder cancer, a considerable number of patients exhibit resistance to the adjuvant treatment with unexplained mechanisms. This study aimed to investigate whether and how androgen receptor (AR) signals modulate BCG cytotoxicity in bladder cancer. AR knockdown or overexpression in bladder cancer lines resulted in induction or reduction, respectively, in intracellular BCG quantity and its cytotoxic activity. Microarray screening identified Rab27b, a small GTPase known to mediate bacterial exocytosis, which was upregulated in BCG-resistant cells and downregulated in AR-shRNA cells. Knockdown of Rab27b, or its effector SYTL3, or overexpression of Rab27b also induced or reduced, respectively, BCG quantity and cytotoxicity. In addition, treatment with GW4869, which was previously shown to inhibit Rab27b-dependent secretion, induced them and reduced Rab27b expression in bladder cancer cells. Meanwhile, AR expression was upregulated in BCG-resistant lines, compared with respective controls. In a mouse orthotopic xenograft model, Rab27b/SYTL3 knockdown or GW4869 treatment enhanced the amount of BCG within tumors and its suppressive effect on tumor growth. Moreover, in non-muscle-invasive bladder cancer specimens from patients subsequently undergoing BCG therapy, positivity of AR/Rab27b expression was associated with significantly higher risks of tumor recurrence. AR activation thus correlates with resistance to BCG treatment, presumably via upregulating Rab27b expression. Mechanistically, it is suggested that BCG elimination from urothelial cells is induced by Rab27b/SYTL3-mediated exocytosis. Accordingly, Rab27b inactivation, potentially via antiandrogenic drugs and/or exocytosis inhibition are anticipated to sensitize the efficacy of BCG therapy, especially in patients with BCG-refractory AR/Rab27b-positive bladder cancer.
虽然膀胱内卡介苗（BCG）免疫疗法已成为非肌层浸润性膀胱癌非手术治疗的金标准，但相当数量的患者对辅助治疗表现出耐药性，其机制尚不清楚。本研究旨在探讨雄激素受体（AR）信号是否以及如何调节膀胱癌中的 BCG 细胞毒性。在膀胱癌系中敲低或过表达 AR，分别导致细胞内 BCG 数量及其细胞毒性活性增加或减少。微阵列筛选鉴定了 Rab27b，一种已知介导细菌胞吐作用的小 GTPase，其在 BCG 耐药细胞中上调，在 AR-shRNA 细胞中下调。Rab27b 的敲低、其效应物 SYTL3 的敲低或 Rab27b 的过表达也分别诱导或减少了 BCG 的数量和细胞毒性。此外，GW4869 处理，先前已显示抑制 Rab27b 依赖性分泌，诱导它们并降低膀胱癌细胞中的 Rab27b 表达。同时，与各自的对照相比，AR 表达在 BCG 耐药系中上调。在小鼠原位异种移植模型中，Rab27b/SYTL3 敲低或 GW4869 治疗增强了肿瘤内 BCG 的数量及其对肿瘤生长的抑制作用。此外，在随后接受 BCG 治疗的非肌层浸润性膀胱癌患者标本中，AR/Rab27b 表达阳性与肿瘤复发风险显著增加相关。AR 激活因此与 BCG 治疗耐药相关，推测可能是通过上调 Rab27b 表达。从机制上讲，BCG 从尿路上皮细胞中的消除是由 Rab27b/SYTL3 介导的胞吐作用诱导的。因此，预计 Rab27b 失活，可能通过抗雄激素药物和/或胞吐作用抑制，可提高 BCG 治疗的疗效，特别是在 BCG 耐药且 AR/Rab27b 阳性的膀胱癌患者中。
