骨肉瘤血管微环境促发c-Met 靶向治疗耐受性的分子机制研究

c-Met is one of oncogenes of osteosarcoma and plays an important role in the generation and malignant process of osteosarcoma, which will be a very promising therapeutic target for osteosarcoma. Our previous studies demonstrated that c-Met inhibitor PF02341066 induced the apoptosis of osteosarcoma cells with high c-Met phosphorylated activity. However, vascular microenvironment significantly reduced the expression and activity of c-Met in osteosarcoma cells, resulting in the originally sensitive osteosarcoma cells acquired the resistance to PF02341066 induced-apoptosis. Our results further showed that c-Met-target therapy could not suppress the osteosarcoma growth in vivo. There were signs that osteosarcoma cells in vascular microenvironment highly expressed VEGFR2 to replace its dependence to c-Met activity. In the present study, we intend to understand the mechanism of vascular microenvironment regulating c-Met pathway; analyze the interaction between c-Met with VEGFR2; explore the role of VEGFR2 signaling on proliferation and tumor recurrence; clarify the effect of VEGFR2 signaling on c-Met-targeted therapy. Our finding should provide the evidence for further understanding the interaction between vascular microenvironment and osteosarcoma cells, and provide theoretical basis for the treatment of osteosarcoma.

c-Met是骨肉瘤的原癌基因，c-Met的异常激活与骨肉瘤患者的不良预后密切相关。因此，靶向c-Met有望为骨肉瘤的治疗提供新思路。项目组的前期动物实验表明，c-Met靶向抑制剂虽然在初期有效抑制骨肉瘤的增殖，但随后对c-Met抑制剂的耐受导致肿瘤的快速反弹复发。体外实验结果也表明，血管微环境不仅下调骨肉瘤细胞中c-Met的表达及其磷酸化活性，激活骨肉瘤细胞的VEGFR2通路，而且促发骨肉瘤细胞获得对c-Met抑制剂的耐受能力。因此，本项目拟分析血管微环境调控骨肉瘤细胞中c-Met通路活性的分子机制；解析c-Met与VEGFR2的相互作用；探索VEGFR2信号通路对促进骨肉瘤细胞增殖和肿瘤复发的分子机理；并进一步阐明VEGFR2信号通路对c-Met受体靶向药物疗效的影响。项目成果将为进一步认识血管微环境与骨肉瘤细胞间的相互作用，探索治疗骨肉瘤的有效方法提供理论基础。

骨肉瘤是青少年中最常见的原发恶性骨肿瘤，具有容易耐药复发和远端转移等不良预后等特点。c-Met是一个关键的癌基因，在靶向治疗骨肉瘤中受到了越来越多的关注。本研究中，我们揭示了c-Met抑制剂PF02341066能够在体外特异性杀伤具有高c-Met磷酸化活性的骨肉瘤细胞。然而在体内实验中，由于受血管微环境的影响，PF02341066不能持续抑制骨肉瘤的生长。临近血管或者形成血管拟态的骨肉瘤细胞，其c-Met表达与c-Met磷酸化活性显著下调。并且，骨肉瘤细胞中VEGFR2表达被激活，从而获得对c-Met抑制剂的耐受性。双靶点抑制c-Met与VEGFR2的磷酸化活性，能够有效缩减小鼠异种移植瘤的体积。对于具有c-Met异常高表达的骨肉瘤患者，或许能够从c-Met靶向治疗联合VEGFR2抑制中受益。总体而言，我们的结果证实了骨肉瘤的肿瘤异质性，以及肿瘤中的血管微环境在c-Met靶向治疗药物耐受中的关键作用，并且揭示了药物耐受的分子机制。