基于双靶向抗体片段的髓源性抑制细胞分子影像以预测肿瘤抗血管生成治疗耐药及疗效

Anti-angiogenic therapy inhibits tumor growth, however, many patients develop resistance and have little effect. Currently, there is no way to predict the response before the administration of medication. Myeloid-derived stem cells (MDSCs) are found to be responsible for the resistance and disease progression through several mechanisms. The number of MDSCs in tumor microenvironment is directly related with resistance to anti-angiogenic therapy. But most studies in this area use the count of MDSCs in peripheral blood or regional tumor site after execution of animal model to estimate the number of MDSCs, lacking an effective way to get the number or distribution of MDSCs throughout the whole body including tumor microenvironment and metastases. We aim to verify the feasibility of in vivo near-infrared fluorescent and PET imaging with bispecific antibody fragments linked by click chemistry targeting monoclonal antibody of MDSCs surface marker CD11b and Gr-1 in the anti-angiogenic resistant tumor model. We intend to explore the association between the pattern of in vivo imaging and tumor growth, MDSCs in the circulation and tumor microenvironment. We are determined to find an noninvasive and in vivo method to reveal the distribution and number of MDSCs over the body and predict the therapy response, which hopefully may make it possible for the individualized and precision therapy.

抗血管生成治疗能抑制肿瘤生长，但部分患者出现耐药，治疗效果不理想。目前尚无方法可以在治疗前预测抗血管生成治疗的疗效。髓源性抑制细胞（MDSCs）通过多种机制介导耐药的产生，促进肿瘤生长与转移。研究表明肿瘤微环境中MDSCs的数量与耐药的产生直接相关，而目前的研究只能用外周血MDSCs计数或者处死动物后取肿瘤标本进行测定，难于在体获得肿瘤微环境及全身转移病灶MDSCs的数量和分布。本研究拟应用点击化学方法连接针对MDSCs表面标志CD11b、Gr-1的双靶向单抗Fab片段，结合近红外荧光成像和PET全身断层显像，在抗血管生成治疗耐药与敏感肿瘤模型中探索分子影像与肿瘤对抗血管生成治疗敏感性、外周血及肿瘤微环境局部MDSCs数量的相关性，建立一种在体无创评估MDSCs分布和数量、预测抗血管生成治疗疗效的新方法，指导肿瘤精准治疗。

抗血管生成治疗能抑制肿瘤生长，但部分患者出现耐药，治疗效果不理想。目前尚无方法可以在治疗前预测抗血管生成治疗的疗效。髓源性抑制细胞（MDSCs）通过多种机制介导耐药的产生，促进肿瘤生长与转移。研究表明肿瘤微环境中MDSCs的数量与耐药的产生直接相关，而目前的研究只能用外周血MDSCs计数或者处死动物后取肿瘤标本进行测定，难于在体获得肿瘤微环境及全身转移病灶MDSCs的数量和分布。本研究应用点击化学方法，连接针对MDSCs表面标志CD11b、Gr-1的单抗Fab片段，成功制备了双靶向抗体片段探针，并进行产物鉴定。并利用近红外荧光成像和PET全身断层显像方法，在抗血管生成治疗耐药肿瘤模型（Lewis细胞系皮下移植瘤）中探索并证明了双靶向抗体片段在体显像的可行性。并发现与完整单抗直接标记显像相比，双靶向抗体片段在肿瘤部位显像效果更好，肝脏摄取更低。目前正在尝试用体外共聚焦免疫荧光成像方法进一步验证双靶向抗体片段分子靶向的正是CD11b、Gr-1双阳性的MDSCs；下一步将通过抗血管生成治疗耐药和敏感的肿瘤模型显像对比，评估显像结果与治疗敏感性的相关性，有望建立在体无创追踪显示MDSCs分布、预测抗血管生成治疗疗效的新方法，实现指导肿瘤精准治疗的意义。

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