长链非编码RNA MACC1-AS1通过EGFRvIII线粒体转位诱导结直肠癌 西妥昔单抗耐药

Cetuximab is a targeted drug for the anti-EGFR treatment of advanced RAS wild-type colorectal cancer. Gradual resistance during treatment is the main cause of treatment failure. Intracellular transport and signal transduction of EGFR is one of the main mechanisms of cetuximab resistance. Studies have shown that EGFR-deleted mutant EGFRvIII can undergo mitochondrial translocation under cetuximab stimulation, but its biological significance is unknown. Our preliminary experimental results showed that EGFRvIII mitochondrial translocation may contribute to endoplasmic reticulum stress tolerance and induce cetuximab resistance in colon cancer cells. Further, the translocation of EGFRvIII is regulated by the upstream LncRNA MACC1-AS1. Downstream, EGFRvIII may participate in the mitochondrial metabolism reprogramming by regulating the activity of the metabolic enzyme PKM2. This suggests that MACC1-AS1 might induce cetuximab resistance through mitochondrial translocation of EGFRvIII that mediates ER stress resistance. This study intends to clarify the role of MACC1-AS1/EGFRvIII/PKM2 signaling axis in cetuximab resistance through ER stress tolerance by means of clinical data analysis, cell and animal models, and molecular biology experiments, which provided new ideas for precision targeting therapy in colorectal cancer treatment.

西妥昔单抗是晚期RAS野生型结直肠癌抗EGFR治疗的靶向药物，治疗过程中逐渐发生的耐药是治疗失败的主因。其中EGFR的胞内转运和信号转导是西妥昔单抗耐药的机制之一。已有研究表明EGFR缺失突变体EGFRvIII在西妥昔单抗刺激下可发生线粒体转位，但其生物学意义不明。我们的预实验结果发现EGFRvIII线粒体转位可能通过内质网应激抵抗，诱导结肠癌细胞西妥昔单抗耐药。进一步，EGFRvIII转位上游受LncRNA MACC1-AS1调控，下游可能调控代谢酶PKM2的活性。由此提出设想：MACC1-AS1是否通过EGFRvIII的线粒体转位，介导内质网应激抵抗而诱导西妥昔单抗耐药？本研究拟通过临床数据分析、细胞和动物模型、分子生物学实验等手段，明确MACC1-AS1/EGFRvIII/PKM2信号轴通过内质网应激抵抗介导西妥昔单抗耐药的机制，为临床上结直肠癌的精准靶向治疗提供新思路。

西妥昔单抗耐药问题是结直肠癌（CRC）靶向治疗领域的热点和难点问题。近期的研究发现西妥昔单抗的作用靶点EGFR存在一种缺失突变亚型EGFRvIII，其能够被西妥昔单抗所阻断，但EGFRvIII的表达与西妥昔单抗疗效的关系未有研究报道。我们发现，EGFRvIII对结肠癌细胞免疫表型的影响具有与野生型EGFR不同的性质，体现在：（1）EGFRvIII通过形成腺苷介导的免疫抑制微环境诱导西妥昔单抗抵抗；（2）相比于EGFRwt，EGFRvIII更加敏感于西妥昔单抗激活的ERS及ICD效应，并促进ATP分泌到胞外；（3）EGFRvIII通过促进stat3磷酸化及入核，上调CD39及CD73表达，进一步增强胞外ATP-腺苷转化。基于此，我们提出：EGFRvIII型结直肠癌细胞通过增强ATP-腺苷转化促进免疫逃逸及西妥昔单抗耐药。本研究 临床数据分析、细胞和动物模型、分子生物学实验等手段，首次证实了EGFRvIII突变影响结直肠癌对西妥昔单抗的敏感性，探索了免疫微环境在靶向治疗耐药中的关键影响，为靶向微环境逆转耐药的策略提供了理论依据。