用一种位点特异性99mTc标记的重组亲和体分子ZHER2:2395靶向HER2表达肿瘤，该亲和体分子C端经工程改造含有半胱氨酸。
Targeting of HER2-expressing tumors with a site-specifically 99mTc-labeled recombinant affibody molecule, ZHER2:2395, with C-terminally engineered cysteine.
作者信息
Ahlgren Sara, Wållberg Helena, Tran Thuy A, Widström Charles, Hjertman Magnus, Abrahmsén Lars, Berndorff Dietmar, Dinkelborg Ludger M, Cyr John E, Feldwisch Joachim, Orlova Anna, Tolmachev Vladimir
机构信息
Department of Medical Sciences, Uppsala University, Uppsala, Sweden.
出版信息
J Nucl Med. 2009 May;50(5):781-9. doi: 10.2967/jnumed.108.056929. Epub 2009 Apr 16.
UNLABELLED
The detection of human epidermal growth factor receptor type 2 (HER2) expression in malignant tumors provides important information influencing patient management. Radionuclide in vivo imaging of HER2 may permit the detection of HER2 in both primary tumors and metastases by a single noninvasive procedure. Small (7 kDa) high-affinity anti-HER2 Affibody molecules may be suitable tracers for SPECT visualization of HER2-expressing tumors. The use of generator-produced (99m)Tc as a label would facilitate the prompt translation of anti-HER2 Affibody molecules into use in clinics.
METHODS
A C-terminal cysteine was introduced into the Affibody molecule Z(HER2:342) to enable site-specific labeling with (99m)Tc. Two recombinant variants, His(6)-Z(HER2:342)-Cys (dissociation constant [K(D)], 29 pM) and Z(HER2:2395)-Cys, lacking a His tag (K(D), 27 pM), were labeled with (99m)Tc in yields exceeding 90%. The binding specificity and the cellular processing of Affibody molecules were studied in vitro. Biodistribution and gamma-camera imaging studies were performed in mice bearing HER2-expressing xenografts.
RESULTS
(99m)Tc-His(6)-Z(HER2:342)-Cys was capable of targeting HER2-expressing SKOV-3 xenografts in SCID mice, but the liver radioactivity uptake was high. A series of comparative biodistribution experiments indicated that the presence of the His tag caused elevated accumulation in the liver. (99m)Tc-Z(HER2:2395)-Cys, not containing a His tag, showed low uptake in the liver and high and specific uptake in HER2-expressing xenografts. Four hours after injection, the radioactivity uptake values (percentage of injected activity per gram of tissue [%IA/g]) were 6.9 +/- 2.5 (mean +/- SD) %IA/g in LS174T xenografts (moderate level of HER2 expression) and 15 +/- 3 %IA/g in SKOV-3 xenografts (high level of HER2 expression). The corresponding tumor-to-blood ratios were 88 +/- 24 and 121 +/- 24, respectively. Both LS174T and SKOV-3 xenografts were clearly visualized with a clinical gamma-camera 1 h after injection of (99m)Tc-Z(HER2:2395)-Cys.
CONCLUSION
The Affibody molecule (99m)Tc-Z(HER2:2395)-Cys is a promising tracer for SPECT visualization of HER2-expressing tumors.
未标记
检测恶性肿瘤中人类表皮生长因子受体2（HER2）的表达可为患者管理提供重要信息。HER2的放射性核素体内成像可通过单一非侵入性程序检测原发性肿瘤和转移灶中的HER2。小分子量（7 kDa）的高亲和力抗HER2亲和体分子可能是用于HER2表达肿瘤SPECT显像的合适示踪剂。使用发生器产生的（99m）Tc作为标记将有助于抗HER2亲和体分子迅速应用于临床。
方法
在亲和体分子Z（HER2:342）的C末端引入半胱氨酸，以便用（99m）Tc进行位点特异性标记。两种重组变体，His(6)-Z(HER2:342)-Cys（解离常数[K(D)]，29 pM）和缺乏His标签的Z(HER2:2395)-Cys（K(D)，27 pM），用（99m）Tc标记，产率超过90%。在体外研究了亲和体分子的结合特异性和细胞处理过程。在携带HER2表达异种移植瘤的小鼠中进行了生物分布和γ相机成像研究。
结果
（99m）Tc-His(6)-Z(HER2:342)-Cys能够靶向SCID小鼠中表达HER2的SKOV-3异种移植瘤，但肝脏放射性摄取较高。一系列比较生物分布实验表明，His标签的存在导致肝脏中积累增加。不含His标签的（99m）Tc-Z(HER2:2395)-Cys在肝脏中的摄取较低，在表达HER2的异种移植瘤中的摄取较高且具有特异性。注射后4小时，LS174T异种移植瘤（HER2表达水平中等）的放射性摄取值（每克组织注射活性的百分比[%IA/g]）为6.9±2.5（平均值±标准差）%IA/g，SKOV-3异种移植瘤（HER2表达水平高）为15±3 %IA/g。相应的肿瘤与血液比值分别为88±24和121±24。注射（99m）Tc-Z(HER2:2395)-Cys 1小时后，用临床γ相机可清晰观察到LS174T和SKOV-3异种移植瘤。
结论
亲和体分子（99m）Tc-Z(HER2:2395)-Cys是用于HER2表达肿瘤SPECT显像的一种有前景的示踪剂。
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