基于PKC/NF-κB-PXR通路调控P-gp的桑皮苷A与紫杉醇联用抗NSCLC增效作用研究

Lung cancer is the leading cause of cancer death in China and throughout the world, and NSCLC accounts for approximately 80% of lung cancer cases with most patients being diagnosed with locally advanced and distant metastatic disease. The decrease of NSCLC cell sensitivity to paclitaxel is the major factor leading to the failure of chemotherapy, and one of the most important mechanisms decreasing NSCLC cell sensitivity to paclitaxel is the P-gp over-expression. The results in our preliminary research demonstrated that Mul A treatment significantly decreased the mRNA and protein expression of P-gp in Caco-2 cells. Furthermore, Mul A treatment displayed apparently inhibitory effect on the function of P-gp both in vitro and in vivo. In addition, activation of PKC activity and NF-κB nuclear translocation were observed in the presence of Mul A, which suggested that PKC and NF-κB might play crucial roles in Mul A-induced suppression of P-gp. Till now, the effect of Mul A on the anti-NSCLC of paclitaxe and the underlying mechanism are still unknown but are worth exploring. Firstly, the synergistic anti-NSCLC between Mulberroside A and paclitaxel will be verified by MTT assay and flow cytometry analysis in A549 cells. Secondly, in order to elucidate the underlying mechanism, siRNA interference and specific inhibitors will be recruited to clarify the signal transduction pathway involved in the synergistic anti-NSCLC between Mulberroside A and paclitaxel. After that, we will conduct a pharmacokinetic study in rat and tumor xenograft experiment to confirm the synergistic anti-NSCLC and its mechanism. The results from this study will be useful to understand the synergistic anti-NSCLC between Mulberroside A and paclitaxe, and provide the novel strategy for improving NSCLC cell sensitivity and rate of chemotherapy success.

非小细胞肺癌（NSCLC）细胞对紫杉醇耐药是造成化疗失败的主要原因，而P-gp是引起多药耐药的重要机制，因此开发基于P-gp抑制的增效剂，是提高紫杉醇对NSCLC化疗成功率的重要策略。我们近期研究发现，桑皮苷A（Mul A）可以下调P-gp的表达水平和外排转运功能，且增强NF-κB和PKC活性，但Mul A能否经由下调NSCLC细胞中P-gp进而增效紫杉醇抗NSCLC作用及其确切分子机制仍不清楚。本项目拟利用细胞存活率检测和流式细胞术明确Mul A对紫杉醇的增效作用，并通过siRNA干扰以及特异性抑制剂揭示Mul A增效紫杉醇的信号通路，同时采用大鼠药动学实验和裸鼠移植瘤抑制实验确证Mul A对紫杉醇的增效作用及其分子机制，最终阐明Mul A增效紫杉醇的抗NSCLC作用及分子机制，为提高NSCLC化疗成功率这一核心问题提供新思路和新策略。

非小细胞肺癌细胞对紫杉醇敏感性降低，造成化疗后出现复发或转移是导致化疗失败的主要原因，课题组前期研究发现桑皮苷A可下调P-gp的表达，且能增强NF-κB和PKC活性，但桑皮苷A能否经由下调NSCLC细胞中P-gp进而增效紫杉醇抗NSCLC作用及其分子机制仍不清楚。因此，本项目以P-gp介导紫杉醇在NSCLC细胞内转运为切入点，探究桑皮苷A是否能作为基于P-gp抑制的增效剂，提高紫杉醇对NSCLC的化疗成功率。主要研究内容为桑皮苷A在体内外对紫杉醇抗NSCLC的增效作用及其分子机制。研究结果显示紫杉醇联用Mul A处理可明显增效紫杉醇的抗A549细胞作用；与紫杉醇单用对比，20 μM和40 μM Mul A与紫杉醇联用可分别使A549细胞48 h存活率显著性下降约20.1%和36.0%。并且Mul A作用后A549细胞中P-gp 的mRNA和蛋白表达均显著下降。研究还发现Mul A可以明显增强细胞中的PKC活性并激活NF-κB通路，其中20 μM和40 μM Mul A能分别使A549细胞中的PKC活性增加2.5和4.3倍。siRNA转染实验表明干扰细胞中PKCα和RelA 均可以显著削弱Mul A对P-gp蛋白表达的下调作用。此外，大鼠药代动力学实验结果显示高剂量的桑皮苷A（40 mg/kg）可显著性的升高紫杉醇的AUC0-12h约2.3倍。本项目成功建立人肺癌A549细胞裸鼠移植瘤模型，利用该模型研究发现联合灌胃桑皮苷A可以增强紫杉醇给药的抑瘤作用。本课题研究及结果为阐明Mul A增效紫杉醇的抗NSCLC作用及分子机制提供了数据支持，为提高NSCLC化疗成功率这一核心问题提供了新思路和新策略。