Metastatic castration-resistant prostate cancer (CRPC) is currently incurable. Cancer growth and progression is intimately affected by its interaction with host microenvironment. Cotargeting of the stroma and prostate cancer is therefore an emerging therapeutic strategy for metastatic CRPC. Cancer-induced osteoclastogenesis is known to contribute to CRPC bone metastasis. This study is to extend pharmacologic value of our synthesized LCC03, a derivative of 5-(2′,4′-difluorophenyl)-salicylanilide that has previously testified for its osteoclastogenesis activity, by exploring its additional cytotoxic properties and underlying mechanism in CRPC cells. LCC03 was chemically synthesized and examined for cell growth inhibition in a serial of CRPC cell lines. We demonstrated that LCC03 dose-dependently suppressed proliferation and retarded cell-cycle progression in CRPC cells. The classical autophagy features, including autophagosome formation and LC3-II conversion, were dramatically shown in LCC03-treated CRPC cells, and it was associated with the suppressed AKT/mTOR signaling pathways, a major negative regulator of autophagy. Moreover, an expanded morphology of the endoplasmic reticulum (ER), increased expression of the ER stress markers GRP78 and PERK, and eIF2α phosphorylation were observed. Blockage of autophagy and PERK pathways using small molecule inhibitors or shRNA knockdown reversed LCC03-induced autophagy and cell death, thus indicating that the PERK–eIF2α pathway contributed to the LCC03-induced autophagy. Furthermore, treatment of tumor-bearing mice with intraperitoneal administered LCC03 suppressed the growth of CRPC xenografts in mouse bone without systemic toxicity. The dual action of 5-(2′,4′-difluorophenyl)-salicylanilide on targeting both the osteoclasts and the tumor cells strongly indicates that LCC03 is a promising anticancer candidate for preventing and treating metastatic CRPC.

中文翻译：

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一种新型水杨酰苯胺衍生物通过内质网应激激活的 PERK 信号通路诱导去势抵抗性前列腺癌的自噬细胞死亡

转移性去势抵抗性前列腺癌 (CRPC) 目前无法治愈。癌症的生长和进展受其与宿主微环境的相互作用的密切影响。因此，基质和前列腺癌的共靶向是转移性 CRPC 的新兴治疗策略。已知癌症诱导的破骨细胞生成有助于 CRPC 骨转移。本研究旨在通过探索其在 CRPC 细胞中的额外细胞毒性特性和潜在机制，扩展我们合成的 LCC03 的药理价值，LCC03 是 5-(2',4'-二氟苯基)-水杨酰苯胺的衍生物，之前已证明其破骨细胞生成活性。LCC03 是化学合成的，并在一系列 CRPC 细胞系中检查细胞生长抑制。我们证明了 LCC03 剂量依赖性地抑制了 CRPC 细胞的增殖并延缓了细胞周期进程。经典的自噬特征，包括自噬体形成和 LC3-II 转化，在 LCC03 处理的 CRPC 细胞中显着显示，并且它与抑制的 AKT/mTOR 信号通路有关，这是自噬的主要负调节因子。此外，观察到内质网 (ER) 的形态扩大、ER 应激标记物 GRP78 和 PERK 的表达增加以及 eIF2α 磷酸化。使用小分子抑制剂或 shRNA 敲低阻断自噬和 PERK 通路逆转了 LCC03 诱导的自噬和细胞死亡，因此表明 PERK-eIF2α 通路有助于 LCC03 诱导的自噬。此外，用腹腔内施用 LCC03 治疗荷瘤小鼠可抑制小鼠骨骼中 CRPC 异种移植物的生长，而没有全身毒性。5-(2',4'-二氟苯基)-水杨酰苯胺对破骨细胞和肿瘤细胞的双重作用强烈表明LCCO3是预防和治疗转移性CRPC的有希望的抗癌候选物。