Molecular Imaging Program at Stanford (MIPS), Department of Radiology and Bio-X Program, Stanford University, California, Stanford, CA 94305-5344, USA.
Amino Acids. 2012 Jul;43(1):405-13. doi: 10.1007/s00726-011-1096-7. Epub 2011 Oct 8.
Molecular imaging of human epidermal growth factor receptor type 2 (HER2) expression has drawn significant attention because of the unique role of the HER2 gene in diagnosis, therapy and prognosis of human breast cancer. In our previous research, a novel cyclic 2-helix small protein, MUT-DS, was discovered as an anti-HER2 Affibody analog with high affinity through rational protein design and engineering. MUT-DS was then evaluated for positron emission tomography (PET) of HER2-positive tumor by labeling with two radionuclides, 68Ga and 18F, with relatively short half-life (t1/2<2 h). In order to fully study the in vivo behavior of 2-helix small protein and demonstrate that it could be a robust platform for labeling with a variety of radionuclides for different applications, in this study, MUT-DS was further radiolabeled with 64Cu or 111In and evaluated for in vivo targeting of HER2-positive tumor in mice. Design 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) conjugated MUT-DS (DOTA-MUT-DS) was chemically synthesized using solid phase peptide synthesizer and I2 oxidation. DOTA-MUT-DS was then radiolabeled with 64Cu or 111In to prepare the HER2 imaging probe (64Cu/111In-DOTA-MUT-DS). Both biodistribution and microPET imaging of the probe were evaluated in nude mice bearing subcutaneous HER2-positive SKOV3 tumors. DOTA-MUT-DS could be successfully synthesized and radiolabeled with 64Cu or 111In. Biodistribution study showed that tumor uptake value of 64Cu or 111In-labeled DOTA-MUT-DS was 4.66±0.38 or 2.17±0.15%ID/g, respectively, in nude mice bearing SKOV3 xenografts (n=3) at 1 h post-injection (p.i.). Tumor-to-blood and tumor-to-muscle ratios for 64Cu-DOTA-MUT-DS were attained to be 3.05 and 3.48 at 1 h p.i., respectively, while for 111In-DOTA-MUT-DS, they were 2.04 and 3.19, respectively. Co-injection of the cold Affibody molecule ZHER2:342 with 64Cu-DOTA-MUT-DS specifically reduced the SKOV3 tumor uptake of the probe by 48%. 111In-DOTA-MUT-DS displayed lower liver uptake at all the time points investigated and higher tumor to blood ratios at 4 and 20 h p.i., when compared with 64Cu-DOTA-MUT-DS. This study demonstrates that the 2-helix protein based probes, 64Cu/111In DOTA-MUT-DS, are promising molecular probes for imaging HER2-positive tumor. Two-helix small protein scaffold holds great promise as a novel and robust platform for imaging and therapy applications.
人表皮生长因子受体 2（HER2）表达的分子成像因其在人乳腺癌的诊断、治疗和预后中的独特作用而受到极大关注。在我们之前的研究中，通过合理的蛋白质设计和工程，发现了一种新型的环 2 螺旋小蛋白 MUT-DS，它是一种具有高亲和力的抗 HER2 Affibody 类似物。然后，通过用两种放射性核素 68Ga 和 18F 标记，对 MUT-DS 进行正电子发射断层扫描（PET）以检测 HER2 阳性肿瘤进行了评估，这些放射性核素的半衰期（t1/2<2 h）相对较短。为了充分研究 2 螺旋小蛋白的体内行为，并证明它可以作为一种强大的平台，用于标记各种放射性核素，以用于不同的应用，在这项研究中，MUT-DS 进一步用 64Cu 或 111In 进行放射性标记，并在携带皮下 HER2 阳性 SKOV3 肿瘤的小鼠中进行体内靶向评估。通过固相肽合成仪和 I2 氧化法化学合成 1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸（DOTA）偶联的 MUT-DS（DOTA-MUT-DS）。然后用 64Cu 或 111In 标记 DOTA-MUT-DS 制备 HER2 成像探针（64Cu/111In-DOTA-MUT-DS）。在携带皮下 HER2 阳性 SKOV3 肿瘤的裸鼠中评估了探针的生物分布和 microPET 成像。DOTA-MUT-DS 可以成功合成，并与 64Cu 或 111In 进行放射性标记。生物分布研究表明，在携带 SKOV3 异种移植瘤的裸鼠中，64Cu 或 111In 标记的 DOTA-MUT-DS 的肿瘤摄取值在 1 h 时分别为 4.66±0.38%ID/g 或 2.17±0.15%ID/g（n=3）。64Cu-DOTA-MUT-DS 的肿瘤与血液和肿瘤与肌肉的比值在 1 h 时分别达到 3.05 和 3.48，而 111In-DOTA-MUT-DS 的比值分别为 2.04 和 3.19。64Cu-DOTA-MUT-DS 与冷 Affibody 分子 ZHER2:342 共注射时，特异性降低了探针在 SKOV3 肿瘤中的摄取，降低了 48%。与 64Cu-DOTA-MUT-DS 相比，111In-DOTA-MUT-DS 在所有研究的时间点均显示较低的肝脏摄取，并且在 4 和 20 h 时具有更高的肿瘤与血液比值。这项研究表明，基于 2 螺旋蛋白的探针 64Cu/111In DOTA-MUT-DS 是一种很有前途的 HER2 阳性肿瘤成像分子探针。2 螺旋蛋白支架作为成像和治疗应用的新型强大平台具有很大的应用前景。
