LKB1/AMPK通过外泌体和自噬决定Wnt3A蛋白的胞吐或降解—神经胶质瘤对贝伐单抗耐药的新机制

Bevacizumab, an anti-angiogenic agent, has been approved by the US Food and Drug Administration for the treatment of glioblastomas. However, “rebound” tumor progression with enhancement of the invasive ability has been observed after cessation of Bevacizumab therapy in patients with glioblastomas. The activation of Wnt/β-catenin pathway through unknown mechanisms has been identified as one of the key reasons for the failure of Bevacizumab treatment. Pre-trial found that lower concentration of Bevacizumab is shown to significantly activate Wnt pathway whereas higher concentration induced autophagy. According to recent studies, we can draw the following conclusions: ①Intercellular communication by tumor-derived exosomes is an important mechanism of tumor resistance. ②Wnt proteins are secreted on exosomes can activate the Wnt pathway in homologous cells. ③The activion of LKB1/AMPK-dependent Autophagy promote the degradation of cell proteins. It is speculated that lower concentration of Bevacizumab can activate Wnt pathway in an exosomes-dependenet manner whereas higher concentration induced LKB1/AMPK-dependent autophagy, which can promote the degradation of Wnt3A. To test this hypothesis, we plan to investigate the mechanism for activating Wnt pathway and the role of autophagy. The results can provide the experimental basis to explain the resistance of glioma to Bevacizumab and might be applied to dose adjustments in clinical therapy.

抗血管生成药贝伐单抗已被批准单药治疗胶质瘤，但临床发现停药后患者可出现肿瘤“反弹”，且侵袭性明显增强。瘤细胞Wnt/β-catenin通路活化已确定是该现象的重要诱因之一，但具体机制未明。预试验发现只有在低浓度时BEV才会显著激活胶质瘤细胞Wnt通路,高浓度则诱导其发生自噬。近来的研究提示:①肿瘤细胞分泌外泌体介导细胞间信息传递是其重要的耐药机制；②外泌体负载的Wnt3A蛋白可活化同源细胞Wnt通路；③LKB1/AMPK活化可诱导自噬而降解胞内蛋白。由此推测BEV低浓度时，瘤细胞通过分泌的外泌体激活Wnt通路，高浓度时则激活LKB1/AMPK诱导自噬，降解Wnt3A而抑制Wnt通路。为验证该假说，计划探讨BEV作用下，瘤细胞Wnt通路活化机制及自噬在其中的作用，研究将围绕LKB1/AMPK调控Wnt3A的胞吐和降解展开，其结果可为解释临床胶质瘤的BEV耐药现象和调整给药策略提供实验依据。

以贝伐单抗为代表的抗血管靶向药物是肿瘤治疗的新希望，但其临床疗效受到肿瘤耐药性的严重制约。本项目以胶质瘤细胞、肺癌细胞、结肠癌细胞和黑色素瘤细胞为模型，分析了贝伐单抗等肿瘤血管生成靶向治疗药物的耐药机制。研究内容围绕肿瘤细胞自噬、凋亡、糖酵解和信号通路(WNT和PI3K/AKT)展开，发现了不同浓度抗血管药物诱导的肿瘤细胞反应差异性及耐药性对肿瘤侵袭和生长的影响。本研究同时分析了临床上与贝伐单抗联合使用的化疗药物奥沙利铂所致结肠癌耐药的机制，提示了二者联合使用所致肿瘤耐药的重叠。此外，通过对WNT和PI3K通路抑制剂的筛选，我们进一步发现一些天然植物提取物可通过抑制代偿活化的信号通路增强抗血管药物及化疗药物的疗效。综上，我们如期完成了课题，部分研究结果已经以论文形式发表。其中，SCI一篇(已录用)，中文期刊5篇。本项目的实施为临床抗血管靶向药物的治疗策略提供了新的思路。