竹节参苷Ⅳa丁酯通过抑制STAT3信号转导通路增强乳腺癌细胞对TRAIL的敏感性研究

TRAIL resistance to many cancer cells is the main reason to hinder TRAIL clinical application. The main cause of TRAIL tolerance results from constitutive STAT3 activation in breast cancer. ChikusetsusaponinⅣa butyl ester is screened as a STAT3 luciferase activity inhibitor from the activity compounds of national traditional Chinese medicine Panax japonicus C. A. Mey, which traditionally exhibits anti-inflammation, anti-cancer and immune-regulation activity. We found that chikusetsusaponinⅣa butyl ester sensitized to TRAIL-induced breast cancer cell apoptosis, indicating that it may enhance TRAIL sensitivity by abrogation STAT3 activation. To further elucidate the mechanism of TRAIL sensitization by chikusetsusaponinⅣa butyl ester, western blot, EMSA, RNA interference, cell apoptosis assay will be used in this project. We will also evaluate the in vivo efficacy of chikusetsusaponinⅣa butyl ester combination with TRAIL in nude mice breast cancer model. This project will not only elucidate the mechanism of TRAIL sensitization by chikusetsusaponinⅣa butyl ester, but also could be guidance for the clinical application of natural STAT3 inhibitor as TRAIL sensitization agents.

肿瘤细胞对TRAIL耐受是阻碍TRAIL临床用药的最主要的原因，STAT3信号通路在乳腺癌细胞中的过度活化是导致其对TRAIL耐受的主要机制。竹节参苷Ⅳa丁酯是从具有抑炎，抗肿瘤及免疫调节作用的民族中药竹节参中通过STAT3荧光素酶报告基因筛选到的具有抑制STAT3转录活力的活性成分。我们发现竹节参苷Ⅳa丁酯能增强乳腺癌细胞对TRAIL的敏感性，提示竹节参参苷Ⅳa丁酯可能通过抑制STAT3介导TRAIL增敏。为了探索竹节参苷Ⅳa丁酯对TRAIL增敏的机理，本课题拟应用Western blot、EMSA、细胞凋亡检测、RNAi等技术研究竹节参苷Ⅳa丁酯调节STAT3信号通路的作用机制，并通过建立裸鼠乳腺癌模型体内评价竹节参苷Ⅳa丁酯对TRAIL的增敏效应。本课题的实施不仅能揭示竹节参苷Ⅳa丁酯对TRAIL增敏的机理，还将为中药活性成分靶向STAT3作为克服TRAIL耐药的临床用药提供新思路。

肿瘤细胞对TRAIL耐受是阻碍TRAIL临床用药的最主要的原因， IL-6/STAT3信号通路的激活与很多肿瘤的发病密切相关，介导了肿瘤细胞异常增殖、侵袭转移、血管生成以及化疗耐药等功能，STAT3信号通路在乳腺癌细胞中的过度活化是导致其对TRAIL耐受的主要机制。以IL-6/STAT3信号通路作为肿瘤分子治疗的靶点，寻找阻断肿瘤细胞中STAT3信号通路的药物对于肿瘤治疗及解决TRAIL耐药具有重要意义。我们从中药竹节参中提取到一种五环三萜的天然化合物竹节参苷Ⅳa丁酯能诱导多种肿瘤细胞的凋亡并且能增强乳腺癌细胞对TRAIL的敏感性，本课题应用了Western blot、EMSA、细胞凋亡检测、RNAi等技术研究了竹节参苷Ⅳa丁酯调节STAT3 信号通路以及介导对TRAIL增敏的作用机制，我们发现竹节参苷Ⅳa丁酯能有效抑制组成型的及IL-6诱导的STAT3信号通路的活化，提示竹节参苷Ⅳa丁酯可能通过抑制STAT3信号通路介导对TRAIL的增敏作用。深入研究发现竹节参苷Ⅳa丁酯能直接作用于IL-6R(结合常数Kd是663.74 nM)，而对IL-6家族其他受体LIFR和 LeptinR的结合能力较IL-6R弱，表明竹节参苷Ⅳa丁酯能选择性地抑制IL-6与IL-6R的结合，抑制IL-6诱导的STAT3信号通路的活化，是一种IL-6R的拮抗剂。我们通过研究进一步揭示了竹节参苷Ⅳa丁酯是通过抑制IL-6/STAT3信号通路进而上调TRAIL受体DR5并下调Mcl-1家族抗凋亡蛋白来介导对TRAIL诱导的凋亡的增敏效应的。本课题的实施不仅揭示了竹节参苷Ⅳa丁酯对TRAIL增敏的机理，还将为中药活性成分靶向STAT3作为克服TRAIL耐药的临床用药提供新思路。