天然黄杨生物碱降解突变p53的抗肿瘤机理研究

P53 is the most important tumor suppressor gene, in cancer cells chaperone Hsp70 and Hsp90 can stabilize mutant p53 by forming complex, the expression of mutant p53 promotes tumor initiation and progression, therefore, mutant p53 is an efficient therapeutic target. We have screened a series of compounds extracted from tranditional Buxus and found that the Buxus alkaloids can simultaneously down regulate the expression of mutant p53 and Hsp90. Therefore, this finding may help to solve the current decreased Hsp90 inhibitor efficacy caused by feedback activation of Hsp90 and Hsp70. This study is to investigate the mechanistic action of mutant p53 degradation pathway such as ubiquitin-proteasom and autophagy with Buxus alkaloids treatment. The p53 conformational change and its down stream signallings pathway are to be studied. In addition, the role of the alkaloids on the effects of p53-Hsp complex is going to be investigated. Moreover, the transcriptional action and phosphorylation of HSF1 will be explored. Finally the anti-tumor effects of the alkaloids will be evaluated in vivo. In conclusion, this cellular, molecular and in vivo study will provide theoretical basis for inventing the natural products with anti-tumor activity.

P53是重要的抑癌基因，肿瘤细胞中p53的突变并与Hsp70、Hsp90形成稳定的复合体，促进了肿瘤的发生、发展。因此，降解突变p53是肿瘤治疗的有效靶点。 前期研究发现天然黄杨生物碱具有同时下调肿瘤细胞突变p53和Hsp90的表达， 而对正常细胞的毒性较小。此类化合物有可能解决目前Hsp90抑制剂治疗肿瘤、因Hsp70和Hsp90被反馈性激活而疗效降低的问题。本项目拟研究黄杨生物碱对突变p53降解通路的泛素化-蛋白酶体及自噬调控; 分析化合物作用后p53构象变化；研究黄杨生物碱对突变p53-Hsp90复合体的干预作用，探讨其对调控Hsp表达的转录因子HSF1的转录功能和磷酸化作用，并进行动物体内抗肿瘤药效评价。 本研究从细胞、分子和体内水平揭示黄杨生物碱抗肿瘤作用，将为研发抗肿瘤天然药物提供理论基础和科学依据。

P53是重要的抑癌基因，肿瘤细胞中p53的突变并与Hsp70、Hsp90形成稳定的复合体，促进了肿瘤的发生、发展。因此，降解突变p53是肿瘤治疗的有效靶点。同时， 恢复突变p53的功能是抗肿瘤药物研究的靶点。本项目探讨了黄杨生物碱KBA01化合物降解突变p53的作用机理主要是通过降低HSF1的表达，打破HSF1-Hsp90-mutantp53复合体从而促使突变p53通过CHIP和MDM2泛素化-蛋白酶体途径降解。除此之外，我们研究发现KBA01可以恢复野生型p53的功能，恢复了p53的DNA结合活性、转录激活功能从而发挥抗肿瘤作用。测序的结果进一步证实了KBA01可以恢复p53功能。 此课题为开发KBA01在突变p53的抗肿瘤作用奠定一定的基础。