含末端半胱氨酸人表皮生长因子受体2亲和体的68Ga标记和显像  

68Ga-labeled HER2 affibody with C-terminal cysteine and its PET imaging

作　　者：蔡炯 党永红 郑堃 吴晨希 朱朝晖 李方 

机构地区：[1]100730,中国医学科学院、北京协和医学院北京协和医院核医学科

出　　处：《中华核医学与分子影像杂志》2013年第6期-,共4页Chinese Journal of Nuclear Medicine and Molecular Imaging

摘　　要：目的 在含末端半胱氨酸的人表皮生长因子受体2(HER2)亲和体的羧基末端甘氨酸-甘氨酸-甘氨酸-半胱氨酸(GGGC)的半胱氨酸残基标记68Ga,探讨该标记物用于乳腺癌模型小鼠的HER2显像.方法 通过基因工程制备含末端半胱氨酸的HER2亲和体,应用1,4,7,10-四氮环十二烷-1,4,7-三乙酸-10-马来酰亚胺乙基乙酰胺(MMA-DOTA)在半胱氨酸巯基上耦联DOTA.新洗脱的68Ga液和DOTA-HER2亲和体在90℃下反应,完成标记.标记产物经过C18柱纯化、乙醇洗脱后用于细胞结合分析和microPET显像.细胞结合分析采用表达HER2的乳腺癌细胞MBA-MD-361,动物模型采用该乳腺癌细胞接种的BALB/c裸鼠模型.于4只荷乳腺癌小鼠尾静脉注射3.7 MBq68Ga标记亲和体,分别于注射后20、60 min进行micmPET显像,随即将动物处死,取出心脏、肿瘤、肌肉、骨骼测质量,并用γ计数仪测量放射性,计算肿瘤与肝脏、肌肉、骨骼、心脏的放射性比值.结果 HER2亲和体纯度在95％以上,68Ga标记亲和体的放化纯为97％.应用HER2阳性细胞测出亲和体的亲和力KD值为1.5 nmoL/L.MicroPET显像示,68Ga标记亲和体进入荷瘤鼠血液循环系统后,很快结合于HER2阳性肿瘤,主要从泌尿系统清除.注射68Ga标记亲和体后,肿瘤与肝脏、肌肉、骨骼、心脏的放射性比值分别为17.4±1.0、35.1±10.9、20.7±6.2和20.9±4.0.结论 68Ga亲和体标记成功,适用于HER2阳性肿瘤的PET显像.Objective To label the modified human epidermal growth factor receptor 2 (HER2) affibody with 68Ga at cysteine position of carboxyl-terminal Gly-Gly-Gly-Cys (GGGC) sequence,and to image the mice model bearing HER2-expressed breast cancer with microPET.Methods The HER2 affibody with carboxyl-terminal cysteine was produced by gene engineering.The 1,4,7,10-tetraazacyclododecane-1,4,7-tris-aceticacid (DOTA) was conjugated to the thiol (SH)-group of cysteine by DOTA-10-maleimidoethylacetamide (MMA-DOTA).The newly eluted 68Ga was labeled to DOTA-HER2 affibody at 90 ℃.The labeled mixture was purified by C18 cartridge and eluted with anhydrous alcohol.The purified 68Ga-labeled affibody was prepared for cell binding analysis and microPET imaging.The HER2-expressed breast cancer cells MBA-MD-361 were used to analyze cell binding and establish cancer model with BALB/c nude mice.68Ga-labeled affibody (3.7 MBq) was administered to 4 nude mice with breast cancer via tail vein for microPET imaging at 20 and 60 min post injection.The mice were sacrificed immediately after imaging in unconscious state and their tissue/organs (tumor,muscle,bone and heart) were removed for weighing and radioactivity counting by γ counter.The tumor to normal organ ratios of radioactivity (tumor to liver,muscle,bone and heart)were calculated.Results The purity of HER2 affibody was more than 95％.The radiochemical purity of 68Ga-labeled HER2 affibody was 97％.The KD value (affinity) of 68Ga-labeled HER2 affibody was 1.5 nmol/L in HER2positive cells.MicroPET imaging showed that 68Ga-labeled HER2 affibody could bind HER2-positive cancer rapidly and excreted mainly through urinary system.The radioactivity ratios of tumor to liver,muscle,bone and heart were 17.4±1.0,35.1±10.9,20.7±6.2 and 20.9±4.0,respectively.Conclusions 68Ga could be labeled to HER2 affibody.The 68Ga-labeled HER2 affibody may be useful for PET imaging of HER2-positive tumor.

关 键 词：乳腺肿瘤 受体 表皮生长因子-尿抑胃素 亲和体 半胱氨酸 镓放射性同位素 放射性核素显像 小鼠 裸 

分 类 号：R737.9[医药卫生—肿瘤] R817.4[医药卫生—临床医学]