Department of Gastrointestinal Surgery, The Second Affiliated Hospital, Jiangxi Medical College, Nanchang University, Nanchang, Jiangxi Province, China.
Jiangxi Province Key Laboratory of Molecular Medicine, The Second Affiliated Hospital, Jiangxi Medical College, Nanchang University, Nanchang, Jiangxi Province, China.
Cell Commun Signal. 2024 Aug 29;22(1):420. doi: 10.1186/s12964-024-01789-2.
Colon cancer is one of the most prevalent tumors in the digestive tract, and its stemness feature significantly contribute to chemoresistance, promote the epithelial-mesenchymal transition (EMT) process, and ultimately lead to tumor metastasis. Therefore, it is imperative for researchers to elucidate the molecular mechanisms underlying the enhancement of stemness feature, chemoresistance, and EMT in colon cancer.
Sphere-formation and western blotting assays were conducted to assess the stemness feature. Edu, flow cytometry, and cell viability assays were employed to evaluate the chemoresistance. Immunofluorescence and western blotting assays were utilized to detect EMT. Immunoprecipitation, ubiquitination, agarose gel electrophoresis, chromatin immunoprecipitation followed by quantitative PCR (chip-qPCR), and dual luciferase reporter gene assays were employed for mechanistic investigations.
We demonstrated a markedly higher expression level of OTUB2 in colon cancer tissues compared to adjacent tissues. Furthermore, elevated OTUB2 expression was closely associated with poor prognosis and distant tumor metastasis. Functional experiments revealed that knockdown of OTUB2 attenuated stemness feature of colon cancer, enhanced its sensitivity to oxaliplatin, inhibited its EMT process, ultimately reduced the ability of tumor metastasis. Conversely, overexpression of OTUB2 exerted opposite effects. Mechanistically, we identified OTUB2 as a deubiquitinase for SP1 protein which bound specifically to SP1 protein, thereby inhibiting K48 ubiquitination of SP1 protein. The SP1 protein functioned as a transcription factor for the GINS1, exerting its regulatory effect by binding to the 1822-1830 region of the GINS1 promoter and enhancing its transcriptional activity. Ultimately, alterations in GINS1 expression directly regulated stemness feature, chemosensitivity, and EMT progression in colon cancer.
Collectively, the OTUB2/SP1/GINS1 axis played a pivotal role in driving stemness feature, chemoresistance, and EMT in colon cancer. These results shed new light on understanding chemoresistance and metastasis mechanisms involved in colon cancer.
结肠癌是消化道最常见的肿瘤之一，其干性特征显著促进化疗耐药性，促进上皮-间充质转化（EMT）过程，最终导致肿瘤转移。因此，研究人员迫切需要阐明增强结肠癌干性特征、化疗耐药性和 EMT 的分子机制。
采用球形成和 Western blot 检测评估干性特征。采用 Edu、流式细胞术和细胞活力检测评估化疗耐药性。采用免疫荧光和 Western blot 检测 EMT。采用免疫沉淀、泛素化、琼脂糖凝胶电泳、染色质免疫沉淀定量 PCR（chip-qPCR）和双荧光素酶报告基因检测进行机制研究。
我们发现 OTUB2 在结肠癌组织中的表达水平明显高于相邻组织。此外，OTUB2 表达升高与不良预后和远处肿瘤转移密切相关。功能实验表明，OTUB2 敲低可减弱结肠癌的干性特征，增强其对奥沙利铂的敏感性，抑制 EMT 过程，从而降低肿瘤转移能力。相反，OTUB2 的过表达则产生相反的效果。机制上，我们发现 OTUB2 是 SP1 蛋白的去泛素化酶，特异性结合 SP1 蛋白，从而抑制 SP1 蛋白的 K48 泛素化。SP1 蛋白作为 GINS1 的转录因子，通过结合 GINS1 启动子的 1822-1830 区域发挥其调节作用，增强其转录活性。最终，GINS1 表达的改变直接调节结肠癌的干性特征、化疗敏感性和 EMT 进展。
综上所述，OTUB2/SP1/GINS1 轴在驱动结肠癌的干性特征、化疗耐药性和 EMT 中发挥关键作用。这些结果为理解结肠癌化疗耐药性和转移机制提供了新的视角。
