RG-I型人参果胶与TRAIL协同抑制人结肠癌细胞增殖及其机制研究

TNF-related apoptosis inducing ligand (TRAIL) is a potent cancer cell-specific apoptosis-induced agent with little to no effect on normal tissues. However, acquired resistance of colorectal cancer cells to TRAIL is a roadblock, limiting the effectiveness of TRAIL in clinical application for colorectal cancer therapy. It is a new hotspot to investigate the synergistic antitumor effect of TRAIL with natural low-toxic molecules thereby augment TRAIL treatment efficacy and suppress the emergence of resistant clones in the colorectal cancer therapy. Ginseng pectin, a major effective component of ginseng, exerts significant anti-tumor effect and also potentiates anti-tumor effect of chemotherapeutic drugs on human colon cancer cells. Our previous work showed that the combination of ginseng RG-I pectin and TRAIL exert significant synergistic inhibitory effect on the proliferation of the TRAIL-resistant colon cancer cells. Thus, we intend to further investigate the mechanism of the synergistic effect including (1) the regulation of ginseng RG-I pectin on the pro-apoptotic proteins and anti-apoptotic proteins in the TRAIL-induced apoptosis pathway and the TRAIL-resistance pathway, (2) the impact of ginseng RG-I pectin on the binding and internalization of the cell-surface galectin-3 with death receptors 5 of TRAIL. (3) test the therapeutic combination effect of ginseng RG-I pectin with TRAIL and the mechanism accounted for the synergistic effect in vivo using mice model bearing xenografted colon tumors and immunohistochemistry respectively. This would be the first study on the synergistic effect of TRAIL and ginseng pectin which is a low-toxic and colon targeting macromolecule. We also comprehensively and systematically studied the mechanism accounted for the synergistic effect on cellular, molecular and in vivo levels. These results will provide a new strategy for the current therapy for colorectal cancer.

寻找毒性较低的天然药物与肿瘤坏死因子相关凋亡诱导配体TRAIL协同进而恢复结肠癌细胞对TRAIL的敏感性是当今本领域的研究热点。我们的前期工作表明从人参果胶中分离得到的I型聚鼠李半乳糖醛酸（RG-I）型果胶可逆转结肠癌细胞对TRAIL的抗药性。在此基础上本项目拟深入研究其机制，包括：(1)RG-I型人参果胶对TRAIL诱导结肠癌细胞凋亡信号通路和细胞产生TRAIL抗药性信号通路的调控；（2）RG-I型人参果胶分子在细胞膜表面的直接作用靶点，包括果胶分子对细胞膜表面的半乳凝集素-3与TRAIL死亡受体DR5的结合及内吞的影响等；（3）采用裸鼠荷瘤模型在活体水平深入研究两者协同抗结肠癌作用及机制。本项目的创新性在于首次采用低毒且能够靶向结肠部位的人参果胶和TRAIL协同抗结肠癌，同时在细胞水平、分子水平和活体水平全面系统地研究两者协同的机制。本研究结果将为结肠癌在临床上的治疗提供新的参考方案。

肿瘤坏死因子相关凋亡诱导配体TRAIL能特异性杀伤肿瘤细胞，对正常细胞鲜有作用，是抗肿瘤的希望药物。但是TRAIL的耐药性限制了其再临床上的应用，寻找毒性低的天然产物与TRAIL协同抗结肠癌是目前本领域的研究热点。我们的前期研究工作表明从人参果胶中分离得到的I 型聚鼠李半乳糖醛酸（RG-I）型果胶3-RG可逆转结肠癌细胞对TRAIL的抗药性。在此基础上，我们首先深入研究其机制发现：RG-I 型人参果胶可诱导结肠癌细胞产生活性氧，进而使JNK和其底物 c-Jun蛋白磷酸化。磷酸化的c-Jun蛋白作为转录因子上调TRAIL 死亡受体DR5表达。采用JNK抑制剂SP600125预处理细胞后，RG-I型人参果胶诱导的DR5的表达及其与TRAIL的协同作用显著下降。其次，我们发现高温修饰后的RG-I 型人参果胶DHCP与TRAIL的协同作用更显著，我们深入研究了其机制并进一步采用裸鼠荷瘤模型在活体水平深入研究两者协同抗结肠癌作用及机制。本项目采用低毒且能够靶向结肠部位的人参果胶和TRAIL 协同抗结肠癌，同时在细胞水平、分子水平和活体水平全面系统地研究两者协同的机制。项目的研究工作取得了一些突破性的进展，研究结果对中药人参的活性机理提供了新的思路，为更好地应用人参提供了新的理论。.除此之外，在项目书原有研究内容的基础上，同时开展了人参皂苷CK、N-糖基化抑制剂衣霉素和EGFR抑制剂吉非替尼与TRAIL的协同抗结肠癌作用及其机制研究。