孕烷X受体介导肝细胞癌分子靶向治疗耐药的调节机制研究

Hepatocellular carcinoma (HCC) is, nowadays one of the most fatal human cancers, and the third most common cause of tumor-related death. Most patients are suffering from the advanced stage of HCC at initial diagnosis, and exhibit dismal clinical outcomes or poor prognosis due to ineffective chemotherapy/MDR. Although recent application of Sorafenib, an oral targeted therapeutic drug or a multi-target protein kinase inhibitor, decreases tumor growth and metastasis, and improves longevity and quality of life for patients, several problems still remain during its usage, with the five-year survival rate of HCC patients being very low. Its efficacy remains moderate and increasing evidence has confirmed that rapid development of drug resistance to Sorafenib also hinders the effectiveness of HCC treatments. Identification of potential mechanisms or therapeutic strategies to overcome the unanticipated efficacy-loss of Sorafenib is valuable. . Recently, we identified a potential mechanism about how HCC obtains drug resistance against Sorafenib through Pregnane X receptor (PXR). PXR is a nuclear receptor that senses the presence of foreign toxic substances including drugs and upregulates the expression of proteins involved in drug metabolism, detoxification and clearance process. Immunoprecipitation (IP) and liquid chromatography tandem mass spectrometry (LC-MS/MS) have demonstrated that Sorafenib exhibits high affinity to PXR, and functions as PXR’s potential ligand. Based on these data, this project aims as (1) identifying the effect of Sorafenib on transcription factor activity of PXR; (2) revealing the effect of PXR on Sorafenib’s efficacy and (3) detecting whether PXR and its downstream genes accelerate Sorafenib's metabolism. Our study may indicate that a novel molecular mechanism of Sorafenib resistance in HCC mediated by PXR activation offering a potential to target the drug resistance pathway and improve future HCC’s treatment outcome.

分子靶向药物索拉非尼（Sorafenib）治疗肝细胞癌（HCC）患者的临床疗效存在个体差异，在治疗过程中大部分对索拉非尼初始敏感的患者也会出现耐药。目前，索拉非尼耐药的分子机制尚未阐明，是亟需解决的热点研究问题。我们的前期研究显示：作为外源性药物与毒物代谢与清除的调控枢纽，孕烷X受体（PXR）可能是影响索拉非尼临床疗效的重要调控分子。基于分子肿瘤学、肿瘤药理学、小动物活体成像以及液相色谱-质谱联用等研究技术，本项目重点开展以下方面的研究工作：（1）检测索拉非尼对PXR转录因子活性和PXR下游相关耐药基因表达的影响；（2）确定PXR表达与活性对索拉非尼抑制HCC作用的影响，探索PXR作为HCC新型治疗/干预靶标的意义；（3）明确PXR加速索拉非尼代谢与清除的具体机制。本项目将为今后提高HCC患者分子靶向治疗的临床应答率和研究开发新的治疗策略提供理论和实验依据。

本项目系统以下方面的研究工作：（1）检测Sorafenib对PXR转录因子活性和PXR下游相关耐药基因表达的影响；（2）确定PXR表达与活性对Sorafenib抑制HCC作用的影响，探索PXR作为HCC新型治疗/干预靶标的意义；（3）明确PXR加速Sorafenib代谢、降解与清除的具体机制。课题按原计划执行，并已全部预期研究工作，通过本项目的顺利实施已取得了诸多研究成绩：（1）临床标本中高PXR水平与索拉非尼治疗的患者预后不良有关；索拉非尼与PXR结合并激活PXR途径，通过上调PXR的转录因子活性诱导HCC细胞对索拉非尼的耐药性。PXR能够诱导HCC细胞对分子靶向药物索拉非尼治疗的耐药，相关研究工作已发表SCI收录的研究论著；（2）转录因子ETS-1是HCC细胞转移与侵袭的主要调节因子。ETS-1高表达与接受索拉非尼治疗的晚期HCC患者预后负相关。ETS-1直接与核孕烷X受体（PXR）结合并增强PXR的转录因子活性，从而进一步诱导PXR的下游多药耐药相关基因的表达水平，最终加速了索拉非尼在HCC细胞中的代谢清除，相关研究工作已发表SCI收录的研究论著；（3）本研究成功利用蛋白晶体的X射线衍射技术解析了PXR的三维结构，为今后研究和开发靶向PXR的药物奠定了坚实基础，相关研究工作已发表中文核心研究论著；（4）鼠李素（rhamnetin）能够降低PXR耐药相关下游基因的表达（cyp3a4 [细胞色素P-450]或mdr-1 [多药耐药性1]）。鼠李素通过抑制Sirt1激活以上调P53的373位点乙酰化上调P53的活性，最终诱导miRNA-148a表达。miR-148a能够作用于PXR的3’UTR。鼠李素通过诱导miR-148a的表达下调PXR的表达水平，最终上调HCC细胞对分子靶向药物的敏感性，相关研究工作已发表研究论著：合计发表SCI研究论著3篇（总影响因子为14.426）、中文核心论著（科技核心）1篇以及Pubmed收录的英文论著2篇。