极性基因Scribble通过活化NOX-ROS信号通路调控肺癌化疗敏感性的分子机制研究

Disruption of cell polarity is an important hallmark of cancer. A set of crucial polarity proteins are known as tumor suppressors based upon studies in Drosophila. The role polarity protein Scribble plays during tumorigenesis in mammals is still poorly understood. The appearance of cancer cell population loss sensitivity to chemotherapeutic agents represents a major problem in the treatment of cancer patients. The regulation of oxidative stress is an important factor in tumour responses to anticancer therapies. In fact, many antitumor agents, such as cisplatin, vinblastine, doxorubicin, camptothecin, neocarzinostatin and many others exhibit antitumor activity via ROS-dependent activation of apoptotic cell death, suggesting potential use of ROS as an antitumor principle. Thus, a unique anticancer strategy named "oxidation therapy" has been developed by inducing cytotoxic oxystress for cancer treatment. Drug resistance,the principal mechanism by which cancer develop resistance to chemotherapy drugs, is a major factor in the failure of chemotherapy. We generated several drug-resistant cancer cell lines, We demonstrated that downregulation of Scribble induced cisplatin-related drug resistance in those cells. This approach shows that decreased sensitivity to drug mediated by the loss of expression of Scribble, is one mechanism that tumor cells use to escape death induced by chemotherapeutic agents. However, the molecular mechanism by which Scribble regulates drug sensitivity to anti-cancer treatment has remained elusive. We showed that downregulation of Scribble conferred increased cisplatin resistance by blocking NOX-derived ROS signaling and apoptosis. This study will focuses on the pathologic role of the Scribble in lung cancer and on the potential therapeutic implication of targeting this axis for the treatment. we will demonstrated that Scribble binding to NADPH oxidase was critical for the generation of reactive oxygen species and cisplatin-induced apoptosis. . This work reveals a potential mechanism whereby polarity protein Scribble involves in redox signaling of cancer cells and impacts on redox-sensitive pathologies, such as resistance to apoptosis after treatment of NSCLC.Our study will enable us to predict the clinical effect of chemotherapy and, provides an effective and pivotal target for the development of new antitumor drugs.

极性基因 Scribble是一种抑癌基因，极性基因异常在肿瘤中的重要作用近年来受到很大关注，但认识还非常有限。我们预实验发现Scribble基因与非小细胞肺癌对顺铂敏感性密切相关。近年Tak Mak综述道ROS信号在决定肿瘤化学疗效中具有重要作用，顺铂等均可通过ROS起作用。而NOX家族是重要的ROS信号来源。我们初步的研究结果提示Scribble可与NOX家族核心蛋白p22phox结合，从而活化NOX亚基以及导致ROS信号蓄积，触发肿瘤细胞对顺铂发生凋亡，最终影响肿瘤细胞对化疗药物的敏感性；而回复Scribble水平显示其顺铂的敏感性明显上升。我们将探讨Scribble与NOX作用与Rac1活化的分子机制，以及Scribble在调控NOX蛋白泛素化降解的机制。并且探讨临床上Scribble作为肺癌化疗敏感性标志物以及预后指标的可能性，并为探索临床化疗敏感性提供新的治疗靶点。

肺癌是目前全球发病率、死亡率最高的恶性肿瘤，其中非小细胞肺癌（non-small cell lung cancer, NSCLC）占所有肺癌患者的85%，严重威胁人类健康。含铂类药物化疗是NSCLC一线化疗的主要治疗手段，顺铂应用最为广泛。但是顺铂耐药普遍发。如何保证NSCLC患者更好的响应顺铂化疗、提高预后并实现个性化治疗仍然是亟待解决的重要问题。极性蛋白Scribble（Scrib）是极性蛋白复合物Scribble/Discs large (Dlg) /Lethal giant larvae (Lgl)中的重要组成成分，定位在上皮细胞顶端部位。Scribble的错位和缺失存在于多种恶性肿瘤中，对肿瘤细胞增殖、肿瘤转移和耐药有促进作用。但是Scribble在NSCLC化疗耐药（尤其是顺铂耐药）中的作用机制仍知之甚少。..我们利用临床收集的NSCLC患者的化疗前肿瘤组织样本，分析Scribble蛋白水平与铂类药物化疗预后的相关性；并发现在NSCLC组织样本和耐药细胞株中，Scribble与NRF2/PDL-1显著负相关。进一步证明了Scribble与顺铂敏感性负相关。体外实验显示，Scribble与Nox2在细胞膜上共定位，而Scribble通过LRR结构域与Nox2相结合并增强Nox2蛋白稳定性。在顺铂处理的NSCLC细胞中，Scribble对Nox2蛋白的稳定有利于ROS的大量产生进而促进细胞凋亡，增强顺铂敏感性。Nrf2（Nuclear factor, erythroid 2 like 2）是ROS的重要调节因子；在黑色素瘤中Nrf2上调PD-L1表达且PD-L1促进肺癌化疗耐药产生。我们利用数据库分析和Kras肺癌模型小鼠，发现在NSCLC组织样本和耐药细胞株中，Scribble与NRF2/PDL-1显著负相关。体外研究发现，Scribble通过抑制Nrf2转录进而降低PD-L1水平，而且Scribble对Nrf2/PD-L1的负向调控部分依赖Scribble/Nox2/ROS信号通路。我们的研究发现了Scribble调控NSCLC顺铂化疗敏感性的作用和机制，而Scribble高表达的NSCLC患者在铂类药物化疗中预后较好，而Scribble低表达的NSCLC患者应更倾向于选择基于PD-L1/PD-1免疫抑制剂的免疫治疗，为实现NSCLC个性化治疗提供靶标。