SIRT1抑制由SCFβ-TrCP1介导的泛素化依赖性XRCC1降解促进顺铂化疗耐药

Cisplatin-based combination chemotherapy has greatly extended the survival of lung cancer patients. However, the efficacy and application of Cisplatin-based chemotherapy scheme is often limited because of the emergence of drug resistance. Therefore, it is valuable to clarify molecular mechanism of cisplatin resistance and develop novel therapeutic approaches to reverse cisplatin resistance. Our preliminary experiments found the deacetylation enzyme SIRT1 was high expressed in cisplatin resistant lung cancer cells, and knockdown SIRT1 can effectively reverse cisplatin resistance by promoting XRCC1 degradation. Once the E3 ligase SCFβ-TrCP1 was knocked down, SIRT1 inhibited failed to reduce XRCC1 protein levels. Treatment with si-β-TrCP1 inhibited cisplatin resistance cells apoptosis. Therefore, we proposed that SIRT1 inhibits SCFβ-TrCP1-mediated ubiquitination-dependent degradation of XRCC1 to promote cisplatin resistance in lung cancer. To prove it, we will perform a series of experiments to clarify the function and relevance of SIRT1 to cisplatin resistance in lung cancer, the effect of SIRT1 on XRCC1 protein degradation mediated by E3 ligase SCFβ-TrCP1. By doing so, we believe that this study will enrich our understanding on drug resistance and ubiquitination-dependent protein degradation, and provide valuable information for the development of novel approaches to reverse drug resistance.

尽管顺铂为基础的化疗方案疗效显著，但顺铂耐药性的产生可导致化疗失败，限制了顺铂在治疗中的应用。目前顺铂耐药的分子机制尚不明确，导致临床上缺泛有效的逆转策略。我们预实验发现去乙酰化酶SIRT1在顺铂耐药细胞中高表达，抑制其活性能增强DNA修复因子XRCC1的乙酰化，促进其降解从而逆转耐药；一旦敲低E3泛素连接酶SCFβ-TrCP1，SIRT1抑制剂不再能诱导XRCC1的泛素化依赖性降解；敲减β-TrCP1抑制顺铂耐药细胞凋亡。因此，我们认为：SIRT1通过抑制由SCFβ-TrCP1介导的泛素化依赖性XRCC1降解来促进肺癌顺铂耐药。本项目将解析SIRT1在肺癌顺铂耐药的作用及其机制，阐明SIRT1去乙酰化XRCC1阻滞E3泛素连接酶SCFβ-TrCP1依赖性降解的机制，揭示SCFβ-TrCP1调控XRCC1稳定性在肿瘤细胞顺铂耐药中的作用，从而为逆转肺癌顺铂耐药提供新的理论依据和治疗靶点。

化疗是治疗肿瘤的主要手段之一，但肿瘤对化疗药物的耐受性抵抗可导致化疗失败。但目前肿瘤耐药机制尚未完全阐明，导致目前临床上尚无有效的肿瘤耐药逆转手段。顺铂是一种广谱的抗癌化疗药物，但肿瘤具有异常的DNA修复能力，可导致顺铂诱导DNA损伤的修复，导致化疗失败。研究表明翻译后修饰在肿瘤的发生发展过程中起着重要作用。.本研究聚焦于DNA损伤的修复因子XRCC1，研究了XRCC1的翻译后修饰乙酰化和泛素化修饰对XRCC1的调控研究。在前期研究基础上，本研究验证了“SIRT1通过去乙酰化XRCC1抑制了SCFβ-TrCP1E3泛素连接酶对XRCC1的泛素化降解，导致XRCC1表达增加，促进肺癌顺铂耐药性的发生”的科学假说。通过项目研究得到以下科学结论：一、SIRT1促进肺癌细胞顺铂耐药；二、敲降SIRT1和SIRT1抑制剂可以逆转肺癌细胞顺铂耐药；三、SIRT1通过抑制XRCC1泛素化降解促进XRCC1的稳定性;四、β-TrCP 是 XRCC1泛素化降解的E3酶，SIRT1去乙酰化XRCC1影响XRCC1与β-TrCP的结合。.上述科学结论，撰写为下列论文，已发表。Yousafzai N A, Zhou Q, Xu W, Shi Q, Xu J, Feng L, Chen H, Shin V Y, Jin H, Wang X. SIRT1 deacetylated and stabilized XRCC1 to promote chemoresistance in lung cancer [J]. Cell Death & Disease 2019, 10(5): 1-12...本研究高表达SIRT1和XRCC1促进肺癌顺铂耐药机制的阐明，不仅有助于深入研究肿瘤顺铂耐药的基础理论，对于临床肿瘤顺铂耐药的诊疗也具有十分重要的意义，可能为顺铂耐药提供新的治疗思路。