肾上腺髓质素ADM介导M2型肿瘤相关巨噬细胞促胶质瘤干细胞放疗抵抗的作用机制研究

Radiation resistance significantly contributes to glioblastoma (GBM) recurrence and dismal patient outcome, which may be closely associated with the role of glioma stem cells (GSCs). Investigations of the mechanisms that drive GSC-mediated radiation resistance and the indicated therapeutic approach are of critical translational significance. Our previous studies have demonstrated that M2 tumor-associated macrophages (M2 TAMs) are crucially important to support GSC maintenance and their malignant behaviors. However, the role of M2 TAMs on GSC-mediated radiation resistance and the underlying mechanisms remain largely unknown. Our recent preliminary results reveal that M2 TAMs preferentially express adrenomedullin (ADM) and GSCs highly express the ADM receptor (ADMR). Since exogenous ADM could activate anti-apoptotic pathways of tumor cells to impair cell apoptosis, we propose that M2 TAMs may paracrine abundant ADM which binds to ADMR preferentially expressed in GSCs, thus promote the activation of anti-apoptotic pathways in GSCs and preserve GSCs from radiation-induced cell apoptosis. In this project, we will employ tumor sample analyses, cellular function assays and in vivo therapeutic experiments to address the role of ADM in mediating the effect of M2 TAM on GSC-driven radiation resistance and its therapeutic value. The findings of this study will provide rational to improve the therapeutic efficiency of radiation and to facilitate the development of GSC-targeting therapy.

放疗抵抗是胶质母细胞瘤（GBM）复发致死的重要原因，机制可能与胶质瘤干细胞（GSC）密切相关。深入研究GSC抵抗放疗的诱导因素并探索其阻滞新策略具有重要临床转化意义。我们前期发现，M2型肿瘤相关巨噬细胞（M2 TAM）对维持GSC生存和促进GSC恶性生物学行为十分重要，但M2 TAM对诱导GSC产生放疗抵抗的作用及调控机制尚不清楚。近期预实验提示，M2 TAM高表达肾上腺髓质素（ADM），而GSC高表达ADM受体（ADMR）。鉴于外源性ADM能活化抗凋亡信号通路并抑制肿瘤细胞凋亡，我们推测M2 TAM能大量分泌ADM并与其表达于GSC的受体ADMR结合，激活抗凋亡通路并诱导GSC产生放疗抵抗。本课题将通过临床样本检测、细胞功能实验和动物治疗实验，探讨ADM在介导M2 TAM诱导GSC放疗抵抗中的作用、分子机制及治疗意义，为提高GBM放疗效果及研发GSC靶向治疗新策略提供依据。

按原计划完成了所有内容。发现肿瘤相关巨噬细胞（Tumor-associated macrophage，TAM）高表达肾上腺髓质素adrenomedullin (ADM)，促进胶质瘤干细胞（glioma stem cell, GSC）自我更新和放疗抵抗；高表达ADM的胶质母细胞患者放疗预后差。ADM与GSC细胞上高表达的受体CRLR（Calcitonin receptor-like receptor）结合，促进AKT磷酸化和通路活化，是ADM促GSC放疗抵抗的分子基础。采用ADM拮抗剂AMA竞争性拮抗ADM活化效应，能逆转GSC放疗抵抗行为并抑制GSC颅内移植瘤生长（论文撰写中，并基于上述发现申报国家发明专利1项，实质审查阶段）。我们还发现，CCR2阳性外周单核细胞可募集进入血管周区域并极化成为TAM，是胶质瘤内ADM的主要分泌来源。ADM多在血管周区域富集，其表达量与胶质瘤微血管密度、CCR2+ TAM在血管周浸润程度呈正相关关系。ADM-CRLR旁分泌通路介导CCR2+ TAM与血管内皮细胞相互作用，诱导内皮细胞迁移，促进血管生成。ADM拮抗剂AMA可特异性阻断ADM的促血管生成效应，延长荷瘤鼠生存期（论文撰写中，并基于上述发现申请发明专利1项，实质审查阶段）。在本项目资助下，培养国家自然科学基金优秀青年基金获得者1名、中国医师协会脑胶质瘤专业委员会优秀青年科技工作者1名，博士后1名，硕士研究生2名；项目团队成员参与会议交流6次（含会议发言4次）。