细胞凋亡近红外线荧光显像在评价肿瘤放疗早期疗效中的作用

Evaluation of early efficacy of tumor radiation therapy using NIRF imaging

目的:研究近红外线荧光(NIRF)标记的annexin V是否能显示小鼠体内细胞凋亡的情况。方法:合成了Cy5.5-annexin V,并对其体外与磷脂酰丝氨酸(PS)的结合特性进行研究。建立小鼠乳腺癌(MCA29)动物模型,将其分为放射治疗组与非放射治疗组,于放射治疗后6h静脉注射Cy5.5-annexin V,24小时后进行显像,比较两组浓聚Cy5.5-annexin V的差异。结果:Cy5.5-annexin V与PS结合的结合力(Kd)为2.51×10-9,未标记的annexin V与PS的Kd为1.54×10-9,两者间无显著差异,表明经Cy5.5标记后并未改变annexin V与PS的Kd。采用流式细胞检测仪及共聚焦激光扫描显微镜研究表明Cy5.5-annexin V与PS结合的特性与FITC-annexin V相似,说明Cy5.5-annexin V在体外具有鉴别凋亡细胞与正常细胞的能力。小鼠MCA29肿瘤细胞动物模型显像表明经放射治疗后的肿瘤细胞浓聚Cy5.5-annexin V高于未治疗的肿瘤细胞。结论:Cy5.5-annexin V可以用于肿瘤放射治疗的早期疗效评价。

Objective： In order to investigate whether near-infrared fluorescence （NIRF） labeled annexin V could also demonstrate apoptotic cells in small animal model. Methods： Cy5.5-annexin V, a novel NIRF contrast agent was synthesized and characterized. Its binding ability to target apoptotic cells was demonstrated in vitro. MCa-29 tumor cells were inoculated in the hind legs of mice to set up the animal models. The mice were divided into radiation and non-radiation groups. Cy5.5- annexin V was injected into mouse intravenously 6 hours after radiation. The imaging was performed 24 hours after injection. Results： The binding affinity, Kd, to phosphatidylserine（PS） was 2.51nM for the Cy5.5-annexin V and 1.54nM for the unmodified annexin V respectively. The results of flow cytometry and confocal fluorescence microscopy showed Cy5.5-annexin V targeted non-viable mouse thymocytes in similar patterns to FITC-annexin V. Fluorescence images of mice with MCa-29 tumor cells demonstrated that the fluorescence intensity in the radiated tumors was higher than that in untreated tumors. Conclusion： Cy5.5-annexin V could be useful in the early evaluation of radiation effect of the tumor.