整合素αvβ6通过内体介导结肠癌失巢凋亡抵抗的作用机制研究

The resistance of tumor cells to anoikis plays an important role in tumor metastasis, which can be mediated by adhesion molecules. Our 20-year studies of integrins have confirmed that integrin αvβ6 is a key adhesion molecule that promotes malignant progression of colon cancer. Our recent study found that integrin αvβ6 had no significant effect on the survival and apoptosis of colon cancer cells under adherent conditions, but αvβ6 could mediate the anoikis-resistance of colon cancer cells. Under the non-adherent conditions, αvβ6 could not signal through the classical focal adhesion, and we further found that endosomes might be involved in αvβ6-mediated anoikis-resistance. Therefore, we speculated that αvβ6 might recruit relevant proteins and activate downstream pathways through the formation of endosomal complex formed after αvβ6 endocytosis, which mediated anoikis-resistance of colon cancer. This study is a continuation and further research of our preliminary work. To test our hypothesis, clinical specimens, cell experiments and animal models were processed in this study to explore the role and underlying mechanisms of integrin αvβ6 in the induction of anoikis-resistance of colon cancer with the endosomal complex formed after endocytosis of αvβ6 being the research focus, so as to provide valuable experiments and theories for target therapy of colon cancer with αvβ6 and its related proteins as the targets.

肿瘤细胞对失巢凋亡的抵抗在肿瘤转移过程中发挥重要作用，而黏附分子可以介导失巢凋亡抵抗。我们对整合素近20年的研究证实αvβ6是促进结肠癌恶性进展的关键黏附分子。我们近期研究发现，整合素αvβ6对贴壁状态下结肠癌细胞的存活及凋亡没有显著影响，但能够介导结肠癌细胞的失巢凋亡抵抗。而在非粘附状态下，αvβ6无法通过经典的黏着斑发挥作用，我们进一步发现内体可能参与αvβ6介导的失巢凋亡抵抗。因此我们推测，αvβ6有可能通过内吞后形成的内体复合体，募集相关蛋白并激活下游通路，从而介导结肠癌的失巢凋亡抵抗。本研究是前期工作的深化和延续，拟采用临床标本、细胞实验、动物模型等多层次实验，以整合素的内吞过程形成的内体复合体为切入点，揭示整合素αvβ6在结肠癌失巢凋亡抵抗中的作用，明确αvβ6介导失巢凋亡抵抗的具体分子机制，从而为以αvβ6及其相关蛋白为靶点对结肠癌进行靶向治疗提供有价值的实验基础和理论依据。

肿瘤细胞对失巢凋亡的抵抗在肿瘤转移过程中发挥重要作用，而黏附分子可以诱导失巢凋亡抵抗。整合素αvβ6是促进结肠癌进展的关键黏附分子。我们近期研究发现，整合素αvβ6对粘附状态下结肠癌细胞的存活及凋亡没有显著影响，但能够诱导结肠癌细胞的失巢凋亡抵抗。在非粘附状态下，整合素αvβ6无法通过经典的黏着斑发挥作用；而现有研究表明，内体可以作为细胞内的特殊信号平台直接参与肿瘤的发生发展过程，因此我们进一步通过CRISPR/Cas9和磷酸化蛋白芯片等多层次实验，发现在3D培养条件下，整合素αvβ6能够通过内吞过程形成内体复合体，并通过结合位点直接连接并活化ERK2，从而抑制GSK-3β通路和凋亡相关蛋白Caspase 3/9，最终诱导失巢凋亡抵抗。此外，我们通过共培养发现结肠癌细胞能够促进肿瘤微环境中的成纤维细胞分泌IL-6，而IL-6能够以旁分泌的形式，与结肠癌细胞膜的IL-6R结合，进一步激活STAT-3通路从而上调结肠癌细胞中整合素αvβ6的表达，从而促进结肠癌细胞的侵袭和上皮间质转化。本研究是前期工作的深化和延续，明确了整合素αvβ6诱导失巢凋亡抵抗的作用和具体分子机制，揭示了整合素αvβ6在肿瘤相关成纤维细胞与结肠癌细胞“交互对话”中的重要作用，从而为后续以整合素αvβ6为靶点对结肠癌进行靶向治疗提供了有价值的实验基础和理论依据。