p28Gankyrin经由keap1-Nrf2通路正调控肝癌细胞抗氧化应激损伤的机制研究

The homeostasis of cell Reactive Oxygen Species (ROS) is delicately regulated mainly through transcription factors such as Nrf2. While per-oxidative damage always promote carcinogenesis and development of hepatocellular carcinoma(HCC), the cancer cell also " hijacked" this mechanism for its escape from damage induced by oxidative stress and enhanced resistance against chemotherapy. Recently, we found that p28Gank, a novel onco-protein in HCC, could up-regulate the anti-oxidant enzymes, thereby reducing ROS level and protecting the tumor cell from apoptosis. Furthermore, Nrf2, the key molecule for transcription of various anti-oxidant enzymes, is increased by p28Gank. In this project, we would like to confirm the role of Nrf2 in p28Gank induced anti-oxidant up-regulation and clarify its significance and mechanism.The implement of this project is prospected to deepen the knowledge on p28Gank-induced carcinogenesis and identify novel target for reverse of HCC chemotherapy resistance. Our research group has been focusing on P28Gank-centered signalling pathway for years, some achievments of which have been published in peer-viewed journals such Gastrotenterology,Hepatology and Cell Research.The platforms as well as technologies involved in this project are availabe in our lab or through co-operation with other lab.

细胞内活性氧（ROS）的水平受精细调控，一方面失调控引起的氧化应激损伤与细胞的癌变密切相关，另一方面肿瘤细胞又能"劫持"该调控机制应对氧化应激对自身的损伤，提高对化疗药物的耐受性。表达、结构、稳定性等受氧化还原状态影响的Nrf2等转录因子对氧化应激起核心调控作用。我们新近的研究表明，肝癌重要的癌蛋白 p28GANK可通过提高细胞内的抗氧化酶系统，降低细胞内ROS水平，抑制癌细胞发生凋亡。我们还发现，p28GANK通过抑制降解机制，上调对抗氧化酶系统起关键调控作用的Nrf2的水平。所以，我们设想 p28GANK可能通过提高Nrf2参与调节肝癌细胞内氧化应激耐受，从而使细胞在高能量代谢状态和化疗药物压力下下仍然维持细胞活力。本项目拟明确p28GANK经由NRF2调控肝癌细胞氧化应激耐受的作用，阐明调控的作用。项目有助全面认识p28GANK的促癌机制，为研发新的克服肝癌耐药性的药物提供靶标。

本研究主要发现在肝癌组织中gankyrin与Nrf2之间存在正反馈调节，gankyrin可以竞争性结合Keap1蛋白的Kelch结构域，抑制Nrf2与Keap1结合并通过蛋白酶体途径降解，稳定Nrf2的表达；而Nrf2则能够通过结合gankyrin启动子区的ARE元件促进gankyrin的表达。Gankyrin-Nrf2正反馈协同作用诱导下游抗氧化酶靶基因的转录，维持肝癌细胞内的氧化还原稳态，保护细胞免受氧化应激所导致的线粒体损伤和细胞死亡。在大鼠DEN诱癌模型中，Gankyrin与Nrf2随着肝细胞癌发生发展过程中在癌巢组织中相互伴随累积。Gankyrin与Nrf2在人类HCC组织中也存在相关性， Gankyrin与Nrf2高表达患者预后差，存活时间短。项目较系统地阐释了重要的肝癌癌蛋白Gankyrin的新作用机制，丰富了对肝癌恶性进展的机制的认识，为研发新的干预手段提供了线索。