Abstract：
BACKGROUND: Cetuximab (CTX) is an effective targeted drug for the treatment of metastatic colorectal cancer, but it is effective only in patients with wild-type KRAS genes. Even in this subset of patients, the sensitivity of CTX in patients with right hemi-colon cancer is much lower than that in patients with left hemi-colon cancer. This significantly limits its clinical application. Therefore, further elucidation of the underlying molecular mechanisms is needed. N-myc downstream-regulated gene 1 (NDRG1) plays an important role in solid tumor invasion and metastasis, but whether it can influence CTX sensitivity has not been thoroughly investigated.
OBJECTIVE: Our study aimed to identify a novel mechanism by which NDRG1 affects CTX sensitivity.
METHODS: Through mass spectrometry analysis of our previously constructed CTX-resistant RKO and HCT116 cells, we found that the signal transducer and activator of transcription-1 (Stat1) might be a potential target of NDRG1. By knocking out NDRG1 or/and Stat1 genes, we then applied the loss-of-function experiments to explore the regulatory relationship between NDRG1 and Stat1 and their roles in the cell cycle, epithelial-mesenchymal transition (EMT), and the sensitivity to CTX in these two colorectal cancer (CRC) cells. Finally, we used the nude-mouse transplanted tumor model and human CRC samples to verify the expression of NDRG1 and Stat1 and their impact on CTX sensitivity in vivo.
RESULTS: Stat1 was upregulated in CTX-resistant cells, whereas NDRG1 was downregulated. Mechanically, NDRG1 was inversely correlated with Stat1 expression. It suppressed CRC cell proliferation, migration, and invasion, and promoted apoptosis and epithelial-mesenchymal transition (EMT) by inhibiting Stat1. In addition, NDRG1 directly interacted with Stat1 and promoted Smurf1-induced Stat1 ubiquitination. Importantly, this novel NDRG1-dependent regulatory loop also enhanced CTX sensitivity both in vitro and in vivo.
CONCLUSIONS: Our study revealed that NDRG1 enhanced the sensitivity to Cetuximab by inhibiting Stat1 expression and promoting its ubiquitination in colorectal cancer, elucidating NDRG1 might be a potential therapeutic target for refractory CTX-resistant CRC tumors. But its clinical value still needs to be validated in a larger sample size as well as a different genetic background.
OBJECTIVE: Our study aimed to identify a novel mechanism by which NDRG1 affects CTX sensitivity.
METHODS: Through mass spectrometry analysis of our previously constructed CTX-resistant RKO and HCT116 cells, we found that the signal transducer and activator of transcription-1 (Stat1) might be a potential target of NDRG1. By knocking out NDRG1 or/and Stat1 genes, we then applied the loss-of-function experiments to explore the regulatory relationship between NDRG1 and Stat1 and their roles in the cell cycle, epithelial-mesenchymal transition (EMT), and the sensitivity to CTX in these two colorectal cancer (CRC) cells. Finally, we used the nude-mouse transplanted tumor model and human CRC samples to verify the expression of NDRG1 and Stat1 and their impact on CTX sensitivity in vivo.
RESULTS: Stat1 was upregulated in CTX-resistant cells, whereas NDRG1 was downregulated. Mechanically, NDRG1 was inversely correlated with Stat1 expression. It suppressed CRC cell proliferation, migration, and invasion, and promoted apoptosis and epithelial-mesenchymal transition (EMT) by inhibiting Stat1. In addition, NDRG1 directly interacted with Stat1 and promoted Smurf1-induced Stat1 ubiquitination. Importantly, this novel NDRG1-dependent regulatory loop also enhanced CTX sensitivity both in vitro and in vivo.
CONCLUSIONS: Our study revealed that NDRG1 enhanced the sensitivity to Cetuximab by inhibiting Stat1 expression and promoting its ubiquitination in colorectal cancer, elucidating NDRG1 might be a potential therapeutic target for refractory CTX-resistant CRC tumors. But its clinical value still needs to be validated in a larger sample size as well as a different genetic background.
摘要：
背景：西妥昔单抗（CTX）是治疗转移性结直肠癌的有效靶向药物，但它仅对具有野生型KRAS基因的患者有效。即使在这部分患者中，右半结肠癌患者CTX的敏感性远低于左半结肠癌患者。这显著限制了其临床运用。因此,需要进一步阐明潜在的分子机制。N-myc下游调节基因1(NDRG1)在实体瘤的侵袭和转移中起重要作用,但它是否会影响CTX的敏感性尚未被彻底研究.
目的：我们的研究旨在确定NDRG1影响CTX敏感性的新机制。
方法：通过对我们先前构建的CTX抗性RKO和HCT116细胞的质谱分析，我们发现信号转导和转录激活因子-1(Stat1)可能是NDRG1的潜在靶点.通过敲除NDRG1或/和Stat1基因，然后，我们应用功能丧失实验来探索NDRG1和Stat1之间的调节关系及其在细胞周期中的作用，上皮-间质转化（EMT），以及这两种结直肠癌（CRC）细胞对CTX的敏感性。最后,我们使用裸鼠移植瘤模型和人CRC样本来验证NDRG1和Stat1的表达及其对体内CTX敏感性的影响。
结果：Stat1在CTX耐药细胞中上调，而NDRG1下调。机械上,NDRG1与Stat1表达呈负相关。它抑制CRC细胞增殖，迁移,和入侵,并通过抑制Stat1促进细胞凋亡和上皮间质转化（EMT）。此外,NDRG1直接与Stat1相互作用并促进Smurf1诱导的Stat1泛素化。重要的是,这种新的NDRG1依赖性调节环也在体外和体内增强了CTX的敏感性.
结论：我们的研究表明，NDRG1通过抑制Stat1表达并促进其在结直肠癌中的泛素化而增强了对西妥昔单抗的敏感性，阐明NDRG1可能是难治性CTX耐药CRC肿瘤的潜在治疗靶点.但其临床价值仍需要在更大的样本量以及不同的遗传背景下进行验证。
目的：我们的研究旨在确定NDRG1影响CTX敏感性的新机制。
方法：通过对我们先前构建的CTX抗性RKO和HCT116细胞的质谱分析，我们发现信号转导和转录激活因子-1(Stat1)可能是NDRG1的潜在靶点.通过敲除NDRG1或/和Stat1基因，然后，我们应用功能丧失实验来探索NDRG1和Stat1之间的调节关系及其在细胞周期中的作用，上皮-间质转化（EMT），以及这两种结直肠癌（CRC）细胞对CTX的敏感性。最后,我们使用裸鼠移植瘤模型和人CRC样本来验证NDRG1和Stat1的表达及其对体内CTX敏感性的影响。
结果：Stat1在CTX耐药细胞中上调，而NDRG1下调。机械上,NDRG1与Stat1表达呈负相关。它抑制CRC细胞增殖，迁移,和入侵,并通过抑制Stat1促进细胞凋亡和上皮间质转化（EMT）。此外,NDRG1直接与Stat1相互作用并促进Smurf1诱导的Stat1泛素化。重要的是,这种新的NDRG1依赖性调节环也在体外和体内增强了CTX的敏感性.
结论：我们的研究表明，NDRG1通过抑制Stat1表达并促进其在结直肠癌中的泛素化而增强了对西妥昔单抗的敏感性，阐明NDRG1可能是难治性CTX耐药CRC肿瘤的潜在治疗靶点.但其临床价值仍需要在更大的样本量以及不同的遗传背景下进行验证。
