抗癌药物正从传统的细胞毒药物向针对作用机制的新型药物发展，如以基因为靶点的抗癌药物。本课题采用RNA干扰技术，以RNA分子为靶点，设计特异性针对肿瘤相关基因mRNA的小分子siRNA，检测不同siRNA对肿瘤细胞的生长抑制作用，探讨siRNA信号转导机制，对细胞凋亡和细胞周期调控的影响，通过干扰RNA治疗恶性肿瘤，为肿瘤基因治疗提供新的理论基础。

Carcinogenesis is regulated by network of many genes associated with apoptosis, proliferation, cell cycle progression and etc. We synthesized siRNAs against mRNAs of tumor-related genes, including bcl2, cdk2, hras, pkc-a, mdm2 and vegf. These siRNAs were transfected into various tumor cells with liposome, and cytotoxicity of these siRNAs was determined with MTT assay. The results showed that the IC50 values of bcl2-siRNA、mdm2-siRNA、cdk2-siRNA、pkcα-siRNA、hras-siRNA were approximately 200 nM and vegf-siRNA was 2000 nM, respectively. Furthermore, the data showed that the cytotoxicity of mdm2-siRNA was 10-fold higher to p53 wild-type MCF-7 cells than to p53 mutant HT-29 cells, indicating that mdm2-siRNA-mediated cytotoxicity was dependent of p53 signaling pathway. Flow cytometry results revealed that mdm2-siRNA induced cell arrest at G1 phase in a time-dependent manner, and that the proportion of G1 phase was elevated from 49.8% to 83.2% compared with control. Furthermore, the results showed that apoptotic cell death was partially induced after 36 h treatment. These results suggested that mdm2-siRNA could inhibit cell growth and induce cell cycle arrest. The results showed that mdm2-siRNA specifically and effectively inhibited the expression of mdm2 gene in MCF-7 cells. In addition, the knockdown of mdm2 expression

针对mdm2等肿瘤相关基因的mRNA序列设计并合成了相应的siRNA。MTT法检测siRNA活性，结果显示5种siRNA对肿瘤细胞有强的生长抑制作用。mdm2-siRNA对p53野生型MCF-7细胞作用强，对p53突变型HT-29细胞作用弱，显示其抗肿瘤作用依赖于p53途径。mdm2-siRNA导致MCF-7细胞G1期阻滞，凋亡细胞随时间而增加。mdm2-siRNA能特异地降低靶蛋白水平，同时引起周期阻滞和凋亡相关蛋白水平变化，包括p53和p21和Bax蛋白水平明显升高，Bcl-2，NF-κB蛋白水平下降。体内mdm2-siRNA对裸鼠移植性MCF-7肿瘤的生长抑制率可达68%；mdm2-siRNA与丝裂霉素联合应用有协同作用，其肿瘤生长抑制率达89％。研究表明mdm2-siRNA可以特异性地抑制靶蛋白的表达，提高p53的水平，进而诱导细胞周期阻滞和细胞凋亡，且mdm2-siRNA在体内也具有抑制肿瘤生长的作用。因此，mdm2-siRNA可能成为一种新型肿瘤基因治疗药物。