DDR抑制活性的强心苷类分子的作用功效与机制研究

DDR (DNA damage response) inhibitors could make cancer cells more sensitive to the effects of radiotherapy/chemotherapy. Combination of DDR inhibitors with radiotherapy/chemotherapy is viable for the clinical treatment of cancers and could enhance the survival rate. In our previous study, three new cardenolides along with 11 known ones were isolated from the leaves of Calotropis gigantea. All of the isolates were evaluated for cytotoxic activity against cancer cell lines, and all cardenolides tested were found to possess different inhibitory effects from strong to weak. Moreover, pretreatment with coroglaucigenin can delay and inhibit DNA damage repair induced by X-rays in cancer cells. In this project, we will further investigate the cardenolides from Calotropis genus by integrated application of spectral and bioactive screen. Subsequently, the structures modifications of compounds will be carried out. For the discovery of the bioactive compounds with high efficiency and low toxicity, the cytotoxic activities about the isolated and semisynthetic cardenolides will be implemented. From the above results, we expect to obtain some promising lead compounds with DDR inhibited activity and then implement the study of the molecular mechanism. This project, including our previous results and the coming research, will not only lead to the new breakthrough of natural compounds used in cancer therapy, but also have new application value for cardenolides, a class of steroid-like compounds, that are well appreciated in the treatment of congestive heart failure and arrhythmia.

在癌症的放化疗中适当地使用DDR（DNA损伤应答）抑制剂可以增强癌细胞对放化疗的敏感性，从而提高癌症病人的生存机会。前期我们从牛角瓜(Calotropis gigantea)的茎叶中分离得到3个新的和11个已知的强心苷类化合物，并发现它们对肿瘤细胞的增殖有不同程度的抑制作用，其中化合物coroglaucigenin对X-射线诱导的肺癌细胞DNA损伤的修复过程具有延缓作用。本课题拟集成波谱筛选和生物活性跟踪技术，深入挖掘牛角瓜属两种植物中强心苷类活性分子，并对量大的化合物进行结构修饰，进而评价系列强心苷类分子的细胞毒活性，对活性较好的分子进行DNA损伤修复方面的研究，探讨其对DDR通路的影响，明确具有DDR抑制活性的强心苷类分子的作用功效与机制。该研究有望使天然产物在癌症治疗作用中有新突破；也将为这类具有强心作用、临床上主要用以治疗慢性心功能不全的“强心苷类化合物”找到新的应用价值。

强心苷在现代医学中被用于充血性心力衰竭的治疗，并与利尿剂联合使用治疗房颤，以及用于一些心律失常的预防和治疗，如阵发性房性心动过速和心源性休克。我们的研究将其应用范围扩展，使强心苷在作为强心药物的同时，也可以作为抑制肿瘤细胞增殖的药物，并可以用于辅助放射疗法，起到辐射增敏作用。取得的结果如下：.1、强心苷目标分子的快速发现：通过对目标植物牛角瓜的特定分离分析方法，分离得到5种结构类型的强心苷共65个，其中首次发现的新化合物8个。.2、发现两个化合物calotropin（Cg10）和uscharidin（Cg17） 对2种胶质瘤细胞（A172, U251）的增殖抑制活性非常好，其IC50值达到纳摩尔级水平，很有开发潜力。.3、对所测强心苷的构效关系进行了探讨，发现了强心苷中药效基团的一些规律。.4、发现化合物calotropin和uscharidin不但具有细胞毒活性，从辐射增敏剂的角度来看，这些化合物的加入，降低了辐照剂量，也会减少对正常组织或邻近组织的影响，因此具有作为辐射增敏剂的潜力。.5、细胞死亡机理研究证实，这两种化合物能显著诱导细胞周期阻滞在G2/M期，显示出良好的抗癌潜力。.上述研究结果和数据，体现了强心苷在癌症治疗上的科学意义和应用潜力。