Zhang Zhengxing, Amouroux Guillaume, Pan Jinhe, Jenni Silvia, Zeisler Jutta, Zhang Chengcheng, Liu Zhibo, Perrin David M, Bénard François, Lin Kuo-Shyan
Department of Molecular Oncology, BC Cancer Agency , Vancouver, British Columbia V5Z 1L3, Canada.
Chemistry Department, University of British Columbia , Vancouver, British Columbia V6T 1Z1, Canada.
Mol Pharm. 2016 Aug 1;13(8):2823-32. doi: 10.1021/acs.molpharmaceut.6b00428. Epub 2016 Jul 14.
Bradykinin B1 receptor (B1R), which is upregulated in a variety of malignancies, is an attractive cancer imaging biomarker. In this study we optimized the selection of radiolabel-chelator complex to improve tumor uptake and tumor-to-background contrast of radiolabeled analogues of B9958 (Lys-Lys-Arg-Pro-Hyp-Gly-Cpg-Ser-d-Tic-Cpg), a potent B1R antagonist. Peptide sequences were assembled on solid phase. Cold standards were prepared by incubating DOTA-/NODA-conjugated peptides with GaCl3, and by incubating AlOH-NODA-conjugated peptide with NaF. Binding affinities were measured via in vitro competition binding assays. (68)Ga and (18)F labeling experiments were performed in acidic buffer and purified by HPLC. Imaging/biodistribution studies were performed in mice bearing both B1R-positive (B1R+) HEK293T::hB1R and B1R-negative (B1R-) HEK293T tumors. Z02176 (Ga-DOTA-Pip-B9958; Pip: 4-amino-(1-carboxymethyl)piperidine), Z02137 (Ga-NODA-Mpaa-Pip-B9958; Mpaa: 4-methylphenylacetic acid), and Z04139 (AlF-NODA-Mpaa-Pip-B9958) bound hB1R with high affinity (Ki = 1.4-2.5 nM). (68)Ga-/(18)F-labeled peptides were obtained on average in ≥32% decay-corrected radiochemical yield with >99% radiochemical purity and 100-261 GBq/μmol specific activity. Biodistribution/imaging studies at 1 h postinjection showed that all tracers cleared rapidly from background tissues (except kidneys) and were excreted predominantly via the renal pathway. Only kidneys, bladders, and B1R+ tumors were clearly visualized in PET images. Uptake in B1R+ tumor was higher by using (68)Ga-Z02176 (28.9 ± 6.21 %ID/g) and (18)F-Z04139 (22.6 ± 3.41 %ID/g) than (68)Ga-Z02137 (14.0 ± 4.86 %ID/g). The B1R+ tumor-to-blood and B1R+ tumor-to-muscle contrast ratios were also higher for (68)Ga-Z02176 (56.1 ± 17.3 and 167 ± 57.6) and (18)F-Z04139 (58.0 ± 20.9 and 173 ± 42.9) than (68)Ga-Z02137 (34.3 ± 15.2 and 103 ± 30.2). With improved target-to-background contrast (68)Ga-Z02176 and (18)F-Z04139 are promising for imaging B1R expression in cancers with PET.
缓激肽B1受体（B1R）在多种恶性肿瘤中上调，是一种有吸引力的癌症成像生物标志物。在本研究中，我们优化了放射性标记螯合剂复合物的选择，以提高B9958（Lys-Lys-Arg-Pro-Hyp-Gly-Cpg-Ser-d-Tic-Cpg）（一种有效的B1R拮抗剂）放射性标记类似物的肿瘤摄取和肿瘤与背景的对比度。肽序列在固相上组装。通过将DOTA-/NODA缀合肽与GaCl3孵育，以及将AlOH-NODA缀合肽与NaF孵育来制备冷标准品。通过体外竞争结合试验测量结合亲和力。在酸性缓冲液中进行（68）Ga和（18）F标记实验，并通过HPLC纯化。在同时携带B1R阳性（B1R+）HEK293T::hB1R和B1R阴性（B1R-）HEK293T肿瘤的小鼠中进行成像/生物分布研究。Z02176（Ga-DOTA-Pip-B9958；Pip：4-氨基-（1-羧甲基）哌啶）、Z02137（Ga-NODA-Mpaa-Pip-B9958；Mpaa：4-甲基苯乙酸）和Z04139（AlF-NODA-Mpaa-Pip-B9958）以高亲和力（Ki = 1.4 - 2.5 nM）结合hB1R。（68）Ga-/（18）F标记的肽平均以≥32%的衰变校正放射化学产率获得，放射化学纯度>99%，比活度为100 - 261 GBq/μmol。注射后1小时的生物分布/成像研究表明，所有示踪剂均迅速从背景组织（肾脏除外）清除，主要通过肾脏途径排泄。在PET图像中仅肾脏、膀胱和B1R+肿瘤清晰可见。使用（68）Ga-Z02176（28.9±6.21 %ID/g）和（18）F-Z04139（22.6±3.41 %ID/g）时，B1R+肿瘤中的摄取高于（68）Ga-Z02137（14.0±4.86 %ID/g）。（68）Ga-Z02176（56.1±17.3和167±57.6）和（18）F-Z04139（58.0±20.9和173±42.9）的B1R+肿瘤与血液和B1R+肿瘤与肌肉的对比度比值也高于（68）Ga-Z02137（34.3±15.2和103±30.2）。由于改善了靶与背景的对比度，（68）Ga-Z02176和（18）F-Z04139有望用于PET成像癌症中的B1R表达。
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