The Key Laboratory of Experimental Teratology, Department of Pathology, School of Basic Medical Sciences, Ministry of Education, Shandong University, Jinan, 250012, Shandong, China.
Department of Pathology, Qilu Hospital, Shandong University, Jinan, 250012, China.
Cell Commun Signal. 2024 Jun 19;22(1):339. doi: 10.1186/s12964-024-01703-w.
Endocrine resistance driven by sustained activation of androgen receptor (AR) signaling pathway in advanced prostate cancer (PCa) is fatal. Characterization of mechanisms underlying aberrant AR pathway activation to search for potential therapeutic strategy is particularly important. Rac GTPase-activating protein 1 (RACGAP1) is one of the specific GTPase-activating proteins. As a novel tumor proto-oncogene, overexpression of RACGAP1 was related to the occurrence of various tumors.
Bioinformatics methods were used to analyze the relationship of expression level between RACGAP1 and AR as well as AR pathway activation. qRT-PCR and western blotting assays were performed to assess the expression of AR/AR-V7 and RACGAP1 in PCa cells. Immunoprecipitation and immunofluorescence experiments were conducted to detect the interaction and co-localization between RACGAP1 and AR/AR-V7. Gain- and loss-of-function analyses were conducted to investigate the biological roles of RACGAP1 in PCa cells, using MTS and colony formation assays. In vivo experiments were conducted to evaluate the effect of RACGAP1 inhibition on the tumor growth.
RACGAP1 was a gene activated by AR, which was markedly upregulated in PCa patients with CRPC and enzalutamide resistance. AR transcriptionally activated RACGAP1 expression by binding to its promoter region. Reciprocally, nuclear RACGAP1 bound to the N-terminal domain (NTD) of both AR and AR-V7, blocking their interaction with the E3 ubiquitin ligase MDM2. Consequently, this prevented the degradation of AR/AR-V7 in a ubiquitin-proteasome-dependent pathway. Notably, the positive feedback loop between RACGAP1 and AR/AR-V7 contributed to endocrine therapy resistance of CRPC. Combination of enzalutamide and in vivo cholesterol-conjugated RIG-I siRNA drugs targeting RACGAP1 induced potent inhibition of xenograft tumor growth of PCa.
In summary, our results reveal that reciprocal regulation between RACGAP1 and AR/AR-V7 contributes to the endocrine resistance in PCa. These findings highlight the therapeutic potential of combined RACGAP1 inhibition and enzalutamide in treatment of advanced PCa.
晚期前列腺癌（PCa）中雄激素受体（AR）信号通路的持续激活导致内分泌抵抗，这是致命的。因此，深入研究导致 AR 通路异常激活的机制，寻找潜在的治疗策略尤为重要。Rac GTP 酶激活蛋白 1（RACGAP1）是一种特异性 GTP 酶激活蛋白。作为一种新型肿瘤原癌基因，RACGAP1 的过表达与多种肿瘤的发生有关。
使用生物信息学方法分析 RACGAP1 与 AR 以及 AR 通路激活之间表达水平的关系。通过 qRT-PCR 和 Western blot 检测 PCa 细胞中 AR/AR-V7 和 RACGAP1 的表达。通过免疫沉淀和免疫荧光实验检测 RACGAP1 与 AR/AR-V7 的相互作用和共定位。通过 MTS 和集落形成实验进行增益和缺失功能分析，研究 RACGAP1 在 PCa 细胞中的生物学作用。通过体内实验评估 RACGAP1 抑制对肿瘤生长的影响。
RACGAP1 是 AR 激活的基因，在 CRPC 和恩扎卢胺耐药的 PCa 患者中显著上调。AR 通过结合其启动子区域转录激活 RACGAP1 的表达。反过来，核 RACGAP1 与 AR 和 AR-V7 的 N 端结构域（NTD）结合，阻止它们与 E3 泛素连接酶 MDM2 相互作用。因此，这阻止了 AR/AR-V7 在泛素蛋白酶体依赖性途径中的降解。值得注意的是，RACGAP1 与 AR/AR-V7 之间的正反馈环导致 CRPC 的内分泌治疗抵抗。恩扎卢胺与体内胆固醇偶联的 RIG-I siRNA 药物联合靶向 RACGAP1 可显著抑制 PCa 异种移植瘤的生长。
总之，我们的研究结果表明，RACGAP1 与 AR/AR-V7 之间的相互调节导致了 PCa 的内分泌抵抗。这些发现强调了联合 RACGAP1 抑制和恩扎卢胺治疗晚期 PCa 的治疗潜力。
Zotero 插件
