基于PI3K/AKT/mTOR通路白头翁皂苷抗肿瘤物质基础和作用机制研究

The total saponins from Pulsatilla chinensis showed significant antitumor activity, and no obvious toxicities to immune system and hematopoietic function through biological evaluation for antitumor activity and toxicity in vivo and in vitro. The preliminary studies on its antitumor mechanism indicated that the total saponins from Pulsatilla chinensis might be a new depressant of PI3K/AKT/mTOR (phosphatidylinositol 3-kinase/AKT/mammalian target of repamycin) signal transduction pathways, and different from normal cell poisonous antitumor drug. Maker proteins of PI3K/AKT/mTOR signal transduction pathways were activated and increased in serveral tumor cells. PI3K/AKT/mTOR signal transduction pathways are intimately related to several human tumors. PI3K/AKT/mTOR plays a pivotal role in tumor cell proliferation, survival and the enhanced protection of human tumor cells from apoptosis during tumorigenesis. The activation of this pathway leads to neoplasm metastasis and the emergence of drug resistance of several tumors including carcinoma of the lungs. In addition, this signal pathway also promotes formation of tumor new vessels. In all, PI3K/AKT/mTOR pathway for drug targets of research has become a hot research topic in the treatment of cancer. In this project, the inhibitory effects of every compound from the total saponins to PI3K/AKT/mTOR pathways will be evaluated, and a preliminary SAR will be summarized, using cell screening model. Then some new saponins with high inhibitory effects to PI3K/AKT/mTOR pathways will be found, and the antitumor effect and mechanism of these active fractions or compounds will be systemically investigated, using the in vivo model of nude mouse transplanted with tumor cells. From the results of this research, we can obtain some leading compounds or candidate molecules for the research and development of new antitumor drug, which can selectively affect on tumor cells.

PI3K/AKT/mTOR通路标志蛋白在肿瘤细胞比正常细胞表达高,该通路的激活可促进肿瘤的转移和耐药的发生，还可促进肿瘤新生血管的形成，以该通路为靶点的药物研究已成为癌症治疗的研究热点。前期工作提示白头翁总皂苷具有明显的体内外抗肿瘤活性，对免疫和造血系统未表现出明显的毒副作用,不同于普通的细胞毒药物，白头翁总皂苷对PI3K/AKT/mTOR通路具有显著的抑制活性，可能是该通路的新型抑制剂。本课题拟对白头翁总皂苷进行系统的化学成分研究，采用体外筛选模型评价它们对PI3K/AKT/mTOR通路的抑制活性，探索其初步构效关系规律，优选出PI3K/AKT/mTOR通路活性分子（群），并采用裸鼠移植瘤模型评价其体内抗肿瘤作用效果。在此基础上，进一步探索白头翁皂苷抗肿瘤高效低毒的分子机制，为开发高效低毒的癌症治疗新药提供先导化合物或候选药物分子。

前期研究发现白头翁总皂苷具有显著的抗肿瘤作用，初步作用机制研究发现其抗肿瘤作用不是单纯的细胞毒作用，可能与特定的分子通路如PI3K/AKT/mTOR通路相关。在此基础上，采用体内外抗肿瘤活性筛选模型，对白头翁总皂苷活性部位中的含量丰富的单体化学成分进行了较系统的药效学评价，发现其指标性成分—白头翁皂苷B4具有显著的抗肿瘤活性。不同于细胞毒类抗肿瘤药物，白头翁皂苷B4无细胞毒、溶血性和刺激性，其可通过免疫调节作用，改善肿瘤微环境，进而发挥抗肿瘤作用。此外，白头翁皂苷B4还具有显著的抗炎活性，在慢性炎症模型试验中发现其抗炎药效与地塞米松相当，分子作用机制与地塞米松明显不同，毒副作用显著低于地塞米松。目前已发表相关SCI论文3篇，申请发明专利3项，其中两项已转让给医药研发或生产企业（转让经费合计104万元），均已进入新药临床前研究阶段。