SUMO化修饰影响膀胱癌的发生发展和化疗敏感性的研究

Bladder cancer (BC) is the most common human malignancy affecting the urinary system and has no effective therapeutic molecular target so far. Sumoylation is an essential posttranslational modification to help cells respond to stimuli and maintain homeostasis of cellular environment. Abnormal expressiton of sumoylation is observed in various cancer and closely associated with tumorgenesis, progression and chemosensitivity, which has being exploited in anticancer therapies. Our previous results showed that UBC9 and SUMO subtypes, key components of SUMO pathway, were overexpressed in bladder cancer tissues. In particular, the expression level of SUMO2/3 was positively correlated with clinical stages, indicating SUMO pathway plays an important role in tumorgenesis and progression of bladder cancer. The results of MTT and RNA-seq displayed that knocking down SUMO3 by shRNA sensitized bladder tumour cells T24 to the chemotherapy drug. Preliminary study showed that sumoylation has an effect on the stability of critical factors of chemotherapy resistance, e.g ATF4, which could subsequently affect signaling pathways related to bladder cancer chemosensitivity. In this project, we plan to investigate the function and clinical significance of sumoylation in bladder cancer and demonstrate the molecular mechanism underlying the effect of sumoylation on chemosensitivity. We will conduct this project from multiple levels by using Immunohistochemistry, CRISPR-Cas9, Chip-seq, RNA-seqetc. The achievement of our project will provide new ideas for preventing and treating bladder cancer.

膀胱癌是泌尿系统中最常见的恶性肿瘤，目前缺乏有效的分子诊治靶点。SUMO化修饰是蛋白质翻译后修饰的重要形式，对细胞应激起关键保护作用。SUMO通路在多种肿瘤中不正常表达，与肿瘤的发生发展及化疗敏感性密切相关。我们前期研究发现SUMO通路重要分子UBC9，SUMO各亚型在膀胱癌组织异常活化，且SUMO2/3的表达与膀胱癌临床分期显著正相关，提示SUMO通路可能在膀胱癌发生发展中有重要作用。MTT和RNA-seq实验表明，敲低SUMO3的表达，膀胱癌细胞对化疗药物敏感性明显升高，初步研究发现其分子机制可能是SUMO化修饰改变了细胞应激关键保护因子如ATF4的稳定性，进而影响膀胱癌化疗敏感相关信号通路。本课题将采用免疫组化，CRISPR/Cas9，Chip-seq，RNA-seq等技术从多层面研究SUMO化修饰在膀胱癌中的作用，阐明其介导膀胱癌化疗敏感性的分子机制，为临床膀胱癌诊治提供新思路。

膀胱癌是一个具有不同临床病程，不同治疗反应且高度异质的疾病，是泌尿系统中最常见的恶性肿瘤。SUMO化修饰是蛋白质翻译后修饰的重要形式，对细胞应激起关键保护作用。SUMO通路在多种肿瘤中异常表达，与肿瘤的发生发展密切相关。UBC9是SUMO反应中唯一的结合酶，在维持体内平衡和抑制应激反应中发挥关键作用。通过对公共数据库数据的分析，我们发现UBC9在膀胱尿路上皮癌中的表达显著高于癌旁组织，但是其在晚期和高级别肿瘤中低表达。进一步的分子生物学实验表明，UBC9敲除可以抑制细胞增殖和迁移、阻滞细胞周期、促进细胞凋亡同时激活炎症相关基因的表达。内质网应激的中枢分子ATF4是细胞适应应激反应的关键蛋白，本研究通过细胞和动物实验证明ATF4敲除可以抑制膀胱癌T24细胞的生长，增强T24细胞对化疗药物氯喹、二甲双胍和维替泊芬的敏感性，促进细胞凋亡，抑制细胞的成瘤能力。此外，我们通过全转录文库筛选技术找到了ATF4的协同致死基因，初步阐释了ATF4影响膀胱癌的作用机制。综上所述，本研究证实UBC9和ATF4是膀胱癌细胞适应应激反应所必需的。UBC9缺失有助于炎症活化、上皮-间充质转化和干细胞样细胞亚群的形成，导致癌症进展。ATF4下调可抑制细胞增殖、增强药物敏感性、促进凋亡同时减弱细胞的成瘤能力。因此，本研究证实UBC9和ATF4是膀胱癌个性化治疗的新的潜在靶点。

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