基于“线粒体动力学平衡-氧化代谢应激”交互信号揭示黄芩来源PPARγ天然激动剂的抗肝癌作用机制

China has the highest incidence of liver cancer around the world. At present, the first-line therapy for hepatocellular carcinoma is usage of sorafenib combined with chemotherapeutic agents. However, this treatment does not enhance the overall survival of hepatoma patients obviously, and causes drug resistance, severe side effects and expansive cost. Therefore, it will be imperative to develop novel anti-hepatoma drugs with good efficacy and low toxicity. Scutellaria baicalensis is a heat-clearing and detoxifying drug, which is used for the therapy of furuncle, abdominal mass and heat symptom-complex since ancient times. Our previous studies showed that the monomer composition from Scutellaria baicalensis named oroxyloside and its aglycone had strong activities against the growth of human hepatocellular carcinoma with little influence on normal tissue and cells. They activated the metabolic modulator PPARγ, and inhibited aerobic glycolysis. But the anticancer targets of oroxyloside and its aglycone are still unknown. Metabolic reprogramming is the vital feature of cancer, which has close connection with mitochondrial dynamics and is the novel aspect of cancer therapy. Through multidisciplinary approach, this project will search the anti-hepatoma target of oroxyloside and its aglycone and verify it. We will discuss the regulating manner of oroxyloside and its aglycone in mitochondrial dynamic and oxidative metabolism, and clarify the molecular mechanism based on the cross talk between mitochondrial dynamic and oxidative metabolic stress. This project will provide scientific evidences for the clinical usage of Scutellaria baicalensis as well as the modernization of its monomer composition, and supply novel target and lead compounds for hepatoma therapy.

中国是全球肝癌发病率最高的国家。目前肝癌一线治疗为靶向药物索拉非尼联合化疗，但病人生存期并无明显延长，且易发生耐药、副作用大、价格昂贵，故开发有效低毒的新型抗肝癌药物势在必行。黄芩为清热解毒类中药，自古用于治疗疖肿、症瘕等。本项目前期研究发现黄芩的有效单体成分千层纸素苷及苷元具有非常好的抗肝癌活性，且不影响正常细胞和组织；能激活代谢调控因子PPARγ，抑制有氧糖酵解，但其确切机制及靶点依然未知。代谢重编程是肿瘤的重要特征，其调控机制与线粒体动力学密切相关，是癌症治疗的新方向。本项目通过集成代谢组学、分子生物学等多学科方法，寻找并确证千层纸素苷及苷元的抗肝癌靶点，解析其对线粒体动力学及氧化代谢的调控方式，用现代科学方法诠释中药黄芩有效单体基于“线粒体动力学平衡-氧化代谢应激”交互信号的抗肝癌分子机制，为黄芩的临床应用及其有效单体成分的现代化开发提供科学依据，为肝癌治疗提供新靶点和先导化合物。

黄芩为清热解毒类中药，自古用于治疗疖肿、症瘕等。本项目旨在寻找中药黄芩的抗肝癌药效物质基础，并用现代科学方法诠释中药黄芩有效单体基于“线粒体动力学平衡-氧化代谢应激”交互信号的抗肝癌分子机制。研究发现黄芩活性单体OAG及OA均是其体内药效的重要物质基础，对多种人肝癌细胞均显示较强的体内外生长抑制作用，且OAG是OA的体内主要代谢产物。机制研究发现， OAG是PPARγ /ɑ双重激动剂，通过PPAR依赖性和非依赖性方式调控多种代谢酶，诱导糖脂代谢重构，抑制葡萄糖分解代谢，促进脂肪酸β氧化及后续氧化磷酸化，导致ROS升高以及ROS介导的G1期周期阻滞，抑制肝癌细胞生长。OA是GLUT1-线粒体融合的双重抑制剂，一方面OA抑制GLUT1而限制肿瘤细胞对葡萄糖的吸收，另一方面通过干扰CDK9与SIRT1结合，脱磷酸化SIRT1并减少其脱乙酰化酶活性，从而抑制SIRT1的表达及活性；在此基础上进一步抑制SIRT1/PGC1-α/PDK2/PARL轴，抑制人肝癌细胞发生线粒体融合。OA对SIRT1的抑制削弱PGC1-α的去乙酰化及其转录活性，导致PDK2表达下调。PDK2的减少导致PARL发生β切割，其产物PARL-β肽具有核定位倾向和潜在的转录调控功能。PARL-β肽发生核转位后，诱导多种线粒体融合相关蛋白mRNA表达下调，进而抑制线粒体融合。这种双重作用使OA在限制葡萄糖摄取抑制糖代谢、导致肝癌细胞发生代谢应激的同时，通过抑制线粒体融合限制了细胞对低能量状态的适应性，导致肝癌细胞能量缺乏，发挥更强的生长抑制作用。最后，本项目基于OA的抗肝癌分子机制开发了一种具有潜力的GLUT1抑制联合线粒体融合抑制的肿瘤治疗策略，并阐明联合协同增效作用的机制与肿瘤细胞的代谢及线粒体状态密切相关。本项目为黄芩的临床应用及其有效单体成分的现代化开发提供科学依据，也为肝癌治疗提供了靶向代谢重编程及线粒体的新治疗思路和候选药物。