Department of Anatomy, University of Ulsan College of Medicine, 88, Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, Republic of Korea.
Department of Gastric Surgery, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, Republic of Korea.
J Cancer Res Clin Oncol. 2018 Sep;144(9):1649-1663. doi: 10.1007/s00432-018-2683-8. Epub 2018 Jun 12.
Under physiologic conditions, the binding of erythropoietin-producing hepatocellular (Eph) A2 receptor and its ligand ephrinA1 results in decreased EphA2 level and tumor suppression. However, EphA2 and ephrinA1 are highly expressed in human cancers including gastric adenocarcinoma. In this study, we tested our hypothesis that cancer-associated fibroblasts (CAFs) promote gastric tumorigenesis through EphA2 signaling in a ligand-independent manner.
Expression of EphA2 protein in primary tumor tissues of 91 patients who underwent curative surgery for gastric adenocarcinoma was evaluated by immunohistochemistry and western blotting. Conditioned medium of cancer-associated fibroblasts (CAF-CM) was used to evaluate the tumorigenic effect of CAFs on gastric cancer cell lines. Epithelial-mesenchymal transition (EMT), cell proliferation, migration, and invasion were assessed. EphrinA1-Fc ligand was used to determine the suppressor role of EphA2 receptor-ligand binding.
CAF-CM-induced EMT and promoted cancer cell motility even without cell-cell interaction. Treatment with a selective EphA2 inhibitor (ALW-II-41-27) or EphA2-targeted siRNA markedly reduced CAF-CM-induced gastric tumorigenesis. EphrinA1-Fc ligand treatment showing ligand-dependent tumor suppression diminished the EphA2 expression and EMT progression. In contrast, ephrinA1-targeted siRNA did not significantly affect CAF-CM-mediated increases in EphA2 expression and EMT progression. Treatment with VEGF showed effects like CAF-CM in terms of EphA2 activation and EMT progression.
CAFs may contribute to gastric tumorigenesis by activating EphA2 signaling pathway in a ligand-independent manner. Our results suggest that ligand-independent activation of EphA2 was triggered by VEGF released from CAF-CM. Our result may partially explain why ligand-dependent tumor suppressor roles of EphA2 are not evident in gastric cancer despite the prominent level of ephrinA1.
在生理条件下，促红细胞生成素产生肝细胞（Eph）A2 受体与其配体 EphrinA1 的结合导致 EphA2 水平降低和肿瘤抑制。然而，EphA2 和 EphrinA1 在包括胃腺癌在内的人类癌症中高度表达。在这项研究中，我们通过 EphA2 信号在配体非依赖性方式测试了我们的假设，即癌症相关成纤维细胞（CAFs）通过 EphA2 信号促进胃肿瘤发生。
通过免疫组织化学和蛋白质印迹法评估 91 例接受胃腺癌根治性手术的患者的原发性肿瘤组织中 EphA2 蛋白的表达。使用癌症相关成纤维细胞（CAF-CM）的条件培养基来评估 CAFs 对胃癌细胞系的致瘤作用。评估上皮-间充质转化（EMT）、细胞增殖、迁移和侵袭。使用 EphrinA1-Fc 配体来确定 EphA2 受体-配体结合的抑制作用。
即使没有细胞-细胞相互作用，CAF-CM 诱导的 EMT 并促进癌细胞运动。用选择性 EphA2 抑制剂（ALW-II-41-27）或 EphA2 靶向 siRNA 处理可显著减少 CAF-CM 诱导的胃肿瘤发生。用 EphrinA1-Fc 配体处理显示出配体依赖性肿瘤抑制作用，降低 EphA2 表达和 EMT 进展。相比之下， EphrinA1 靶向 siRNA 对 CAF-CM 介导的 EphA2 表达增加和 EMT 进展没有显著影响。VEGF 治疗在 EphA2 激活和 EMT 进展方面具有与 CAF-CM 相似的作用。
CAFs 可能通过以配体非依赖性方式激活 EphA2 信号通路促进胃肿瘤发生。我们的结果表明，CAF-CM 释放的 VEGF 触发 EphA2 的配体非依赖性激活。我们的结果部分解释了为什么尽管 EphrinA1 水平较高，但 EphA2 的配体依赖性肿瘤抑制作用在胃癌中并不明显。
