小鼠HCCLM3肝癌模型中超声分子成像对抗血管生成治疗的早期评价

Molecular ultrasound imaging with VEGFR2-targeted microbubbles in early assessment of antiangiogenic therapy in a mouse liver cancer model

目的:探讨靶向血管内皮生长因子受体2(vascular endothelial growth factor receptor 2,VEGFR2)的超声造影在裸小鼠HCCLM3肝癌移植瘤模型中早期评价贝伐单抗抑制肿瘤血管生成的可行性。方法:采用"生物素-亲和素"桥接法制备携VEGFR2单克隆抗体的靶向超声微泡,建立裸小鼠HCCLM3肝癌皮下移植瘤模型。将荷瘤鼠随机分为治疗组(n=6,贝伐单抗10 mg/kg每周2次,治疗1周)和对照组(n=6,等体积0.9%NaCl溶液给药)。治疗前(第0天)、治疗第2天、治疗第7天行超声造影检查,绘制时间-强度曲线(time-intensity curve,TIC),比较相关定量参数的组间差异及组内各参数的变化,同时采用CD31免疫组织化学染色比较2组间微血管密度(microvessel density,MVD)。结果:治疗第7天,治疗组达峰时间(time to peak,TTP)、平均渡越时间(mean transit time,MTT)较治疗前缩短,曲线下面积(area under curve,AUC)较治疗前减小,差异均有统计学意义(P<0.05);组间比较发现,治疗第7天治疗组流入相曲线下面积(area under wash-in curve,WiAUC)低于对照组[(36.4±11.6) dB·s vs (61.9±12.4) dB·s,P=0.010];免疫组织化学结果显示,治疗组MVD值低于对照组(8.3±2.1 vs 18.4±7.6,P=0.039)。结论:靶向VEGFR2的超声造影可用于早期无创监测裸小鼠HCCLM3肝癌皮下移植瘤模型中抗血管生成治疗反应,TTP、MTT、AUC及WiAUC等定量参数是有效的参考指标。

Objective:To investigate the feasibility of vascular endothelial growth factor receptor 2(VEGFR2)-targeted contrast-enhanced ultrasound in monitoring the efficacy of antiangiogenic therapy in a subcutaneous xenograft tumor model of HCCLM3.Methods:Anti-VEGFR2 monoclonal antibody was conjugated onto the surface of lipid microbubbles by the biotinavidin interaction.The vascular effects of therapy were examined in mice carrying HCCLM3 xenografts.In vivo molecular contrastenhanced ultrasound imaging with VEGFR2-targeted microbubbles was performed before and 2,7 d after bevacizumab or saline treatment.Intratumoral perfusion areas were quantified by binarizing ultrasound images and the microvessel density was observed by CD31 immunohistochemistry.Perfusion parameters derived from time-intensity curve(TIC)were compared between the bevacizumab group and the control group,and longitudinal comparison of the parameters within the two groups was performed.Results:Although tumor volume was not significantly different between the two groups throughout the therapy period,longitudinal analysis of perfusion parameters showed a significant decrease in time to peak(TTP),mean transit time(MTT)and area under curve(AUC)7 d after bevacizumab treatment,but no significant changes appeared in the control group.There was a significant difference in area under the wash-in curve(WiAUC)between the two groups on day 7.Immunohistochemistry confirmed the lower microvessel density in the bevacizumab group.Conclusion:The efficacy of antiangiogenic therapy could be noninvasively monitored with VEGFR2-targeted ultrasound in a murine model of human liver cancer with a significant decline of multiple perfusion parameters.