ADAM12调控EphB2信号通路诱导垂体腺瘤细胞EMT的作用和机制研究

Accumulative studies elucidated that tumor invasion of pituitary adenomas was associated with incomplete tumor resection, tumor recurrence and poor prognosis. Epithelial-mesenchymal transition (EMT) is the initial period and key procedure of tumor invasion. We previously reported that the over-expression of a disintegrin and metalloproteinase 12 (ADAM12) contributed to tumor invasion of pituitary adenomas. A significant EMT phenomenon of pituitary adenoma cells came into sight after ADAM12 up-regulation, which indicated that ADAM12 could induce EMT to promote tumor invasion in pituitary adenomas. However, the potential mechanism has been largely elusive. By employing RTK Phosphorylation Antibody Array, we found that EphB2 might be the target of ADAM12 in pituitary adenomas. Numerous evidence demonstrated that EphB2 signaling pathway plays an important role in EMT. Therefore, this project is to explore the impact of ADAM12 on pituitary adenoma cell EMT in vitro and in vivo, and to address the potential mechanism of ADAM12 regulating EphB2 signaling pathway and its role in pituitary adenoma cell EMT at both molecular and functional levels. This novel study may provide the evidence for defining ADAM12 as a new biomarker and therapeutic target for invasive pituitary adenomas.

肿瘤侵袭是造成垂体腺瘤手术无法根除，导致复发和影响预后的关键因素。EMT是肿瘤侵袭的早期事件和关键环节。我们前期发现ADAM12高表达促进垂体腺瘤侵袭。通过进一步预实验，我们发现上调ADAM12表达，垂体腺瘤细胞出现明显的EMT现象(E-cadherin下调，N-cadherin、Fibronectin上调)。这些结果提示ADAM12能够诱导垂体腺瘤细胞发生EMT促进肿瘤侵袭，然而，其潜在调控机制尚未阐明。利用蛋白芯片筛选我们发现EphB2可能是ADAM12的作用靶点。结合文献报道EphB2信号通路在肿瘤细胞EMT中发挥重要作用。基于此，本项目拟以人垂体腺瘤组织，体外细胞和体内动物为实验对象，采用分子生物学和药物干预等手段，探讨ADAM12调控EphB2信号通路在诱导垂体腺瘤细胞EMT中的作用和分子机制。本项目的完成有望为侵袭性垂体腺瘤提供一个全新的生物标志物和治疗靶点。

肿瘤侵袭是造成垂体腺瘤手术无法根除，导致复发和影响预后的关键因素。EMT是肿瘤侵袭的早期事件和关键环节。本项目以人垂体腺瘤组织，体外细胞和体内动物模型为实验对象，采用分子生物学和药物干预等手段，探讨了ADAM12调控EphB2信号通路诱导垂体腺瘤细胞EMT中的作用和分子机制。我们在人垂体腺瘤组织样本检测中发现，ADAM12在侵袭性垂体腺瘤内特异性高表达，其表达与细胞上皮表型标志物E-cadherin表达负相关，与间质表型标志物Fibronectin表达正相关，提示ADAM12通过诱导垂体腺瘤细胞发生上皮间质转化（EMT）进而促进其侵袭。在体外细胞实验中，我们发现下调ADAM12表达后，垂体腺瘤细胞的形态由间质表型向上皮表型转化，肿瘤的增殖、迁移和侵袭能力显著下降，但凋亡水平未受影响；信号通路筛选发现EphB2受体及其下游ERK1/2的磷酸化程度显著下调，随后，我们在稳定下调ADAM12表达的垂体腺瘤细胞中使用激动剂（ephrinA2-Fc）激活EphB2受体，发现肿瘤细胞形态由上皮表型向间质表型逆转，肿瘤细胞的增殖、迁移和侵袭能力恢复，这些结果提示ADAM12是通过EphB2/ERK信号通路诱导垂体腺瘤细胞发生EMT从而促进其增殖、迁移和侵袭。最后，我们通过动物模型进行验证，发现下调ADAM12表达后，继发瘤体积显著缩小，继发瘤内E-cadherin表达上调，Fibronectin表达下调，Ki-67指数下调，这些结果与体外细胞实验完全吻合。综上所述，我们通过该项目证实了ADAM12通过调控EphB2/ERK信号通路诱导垂体腺瘤细胞发生EMT促进肿瘤侵袭。本项目的完成为侵袭性垂体腺瘤提供一个全新的特异性生物标志物，也为其治疗提供了新的靶点和思路。