18F标记的抗HER2纳米抗体缀合物用于免疫PET成像HER2受体表达的临床前评估
Preclinical Evaluation of 18F-Labeled Anti-HER2 Nanobody Conjugates for Imaging HER2 Receptor Expression by Immuno-PET.
作者信息
Vaidyanathan Ganesan, McDougald Darryl, Choi Jaeyeon, Koumarianou Eftychia, Weitzel Douglas, Osada Takuya, Lyerly H Kim, Zalutsky Michael R
机构信息
Department of Radiology, Duke University Medical Center, Durham, North Carolina
Department of Radiology, Duke University Medical Center, Durham, North Carolina.
出版信息
J Nucl Med. 2016 Jun;57(6):967-73. doi: 10.2967/jnumed.115.171306. Epub 2016 Feb 18.
UNLABELLED
The human growth factor receptor type 2 (HER2) is overexpressed in breast as well as other types of cancer. Immuno-PET, a noninvasive imaging procedure that could assess HER2 status in both primary and metastatic lesions simultaneously, could be a valuable tool for optimizing application of HER2-targeted therapies in individual patients. Herein, we have evaluated the tumor-targeting potential of the 5F7 anti-HER2 Nanobody (single-domain antibody fragment; ∼13 kDa) after (18)F labeling by 2 methods.
METHODS
The 5F7 Nanobody was labeled with (18)F using the novel residualizing label N-succinimidyl 3-((4-(4-(18)F-fluorobutyl)-1H-1,2,3-triazol-1-yl)methyl)-5-(guanidinomethyl)benzoate ((18)F-SFBTMGMB; (18)F-RL-I) and also via the most commonly used (18)F protein-labeling prosthetic agent N-succinimidyl 3-(18)F-fluorobenzoate ((18)F-SFB). For comparison, 5F7 Nanobody was also labeled using the residualizing radioiodination agent N-succinimidyl 4-guanidinomethyl-3-(125)I-iodobenzoate ((125)I-SGMIB). Paired-label ((18)F/(125)I) internalization assays and biodistribution studies were performed on HER2-expressing BT474M1 breast carcinoma cells and in mice with BT474M1 subcutaneous xenografts, respectively. Small-animal PET/CT imaging of 5F7 Nanobody labeled using (18)F-RL-I also was performed.
RESULTS
Internalization assays indicated that intracellularly retained radioactivity for (18)F-RL-I-5F7 was similar to that for coincubated (125)I-SGMIB-5F7, whereas that for (18)F-SFB-5F7 was lower than coincubated (125)I-SGMIB-5F7 and decreased with time. BT474M1 tumor uptake of (18)F-RL-I-5F7 was 28.97 ± 3.88 percentage injected dose per gram of tissue (%ID/g) at 1 h and 36.28 ± 14.10 %ID/g at 2 h, reduced by more than 90% on blocking with trastuzumab, indicating HER2 specificity of uptake, and was also 26%-28% higher (P < 0.05) than that of (18)F-SFB-5F7. At 2 h, the tumor-to-blood ratio for (18)F-RL-I-5F7 (47.4 ± 13.1) was significantly higher (P < 0.05) than for (18)F-SFB-5F7 (25.4 ± 10.3); however, kidney uptake was 28-36-fold higher for (18)F-RL-I-5F7.
CONCLUSION
(18)F-RL-I-5F7 is a promising tracer for evaluating HER2 status by immuno-PET; however, in settings in which renal background is problematic, strategies for reducing its kidney uptake may be needed.
未标记
人表皮生长因子受体2（HER2）在乳腺癌以及其他类型癌症中过度表达。免疫正电子发射断层扫描（Immuno-PET）是一种可同时评估原发性和转移性病变中HER2状态的非侵入性成像程序，可能是优化HER2靶向治疗在个体患者中应用的有价值工具。在此，我们通过两种方法评估了（18）F标记后5F7抗HER2纳米抗体（单域抗体片段；约13 kDa）的肿瘤靶向潜力。
方法
使用新型残留标记物N-琥珀酰亚胺基3-（（4-（4-（18）F-氟丁基）-1H-1,2,3-三唑-1-基）甲基）-5-（胍基甲基）苯甲酸酯（（18）F-SFBTMGMB；（18）F-RL-I）以及通过最常用的（18）F蛋白质标记辅助剂N-琥珀酰亚胺基3-（18）F-氟苯甲酸酯（（18）F-SFB）对5F7纳米抗体进行（18）F标记。为作比较，5F7纳米抗体也使用残留放射性碘化剂N-琥珀酰亚胺基4-胍基甲基-3-（125）I-碘苯甲酸酯（（125）I-SGMIB）进行标记。分别在表达HER2的BT474M1乳腺癌细胞和带有BT474M1皮下异种移植瘤的小鼠中进行了配对标记（（18）F/（125）I）内化试验和生物分布研究。还对使用（18）F-RL-I标记的5F7纳米抗体进行了小动物PET/CT成像。
结果
内化试验表明，（18）F-RL-I-5F7细胞内保留的放射性与共孵育的（125）I-SGMIB-5F7相似，而（18）F-SFB-5F7的细胞内保留放射性低于共孵育的（125）I-SGMIB-5F7，并随时间下降。（18）F-RL-I-5F7在BT474M1肿瘤中的摄取在1小时时为每克组织28.97±3.88注射剂量百分比（%ID/g），在2小时时为36.28±14.10 %ID/g，用曲妥珠单抗阻断后降低超过90%，表明摄取具有HER2特异性，并且也比（18）F-SFB-5F7高26%-28%（P<0.05）。在2小时时，（18）F-RL-I-5F7的肿瘤与血液比值（47.4±13.1）显著高于（18）F-SFB-5F7（25.4±10.3）（P<0.05）；然而，（18）F-RL-I-5F7的肾脏摄取高28-36倍。
结论
（18）F-RL-I-5F7是一种通过免疫正电子发射断层扫描评估HER2状态的有前景的示踪剂；然而，在肾脏本底有问题的情况下，可能需要采取减少其肾脏摄取的策略。
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