PET imaging of very late antigen-4 in melanoma: comparison of 68Ga- and 64Cu-labeled NODAGA and CB-TE1A1P-LLP2A conjugates.
PET imaging of very late antigen-4 in melanoma: comparison of 68Ga- and 64Cu-labeled NODAGA and CB-TE1A1P-LLP2A conjugates.
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DOI：
10.2967/jnumed.114.144881
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发表时间：
2014-11
期刊：
影响因子：
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通讯作者：
Anderson CJ
中科院分区：
文献类型：
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作者：
Beaino W;Anderson CJ
黑色素瘤是一种来源于表皮黑素细胞的恶性肿瘤，它以其侵袭性、治疗抗性和晚期转移倾向而闻名。极晚期抗原-4（VLA-4;也称为整合素α4β1）是一种在黑色素瘤肿瘤中过表达的跨膜非共价异源二聚体，通过促进癌细胞的粘附和迁移在肿瘤生长、血管生成和转移中发挥重要作用。在这项研究中，我们评估了2个共轭物的高亲和力VLA-4肽模拟配体，LLP 2A，PET/CT成像在皮下和转移性黑色素瘤肿瘤。将LLP 2A缀合至1，4，8，11-四氮杂环十四烷-1-（甲烷膦酸）-8-（甲烷羧酸）（CB-TE 1A 1 P）和2-（4，7-双（羧甲基）-1，4，7-三唑烷-1-基）戊二酸（NODAGA）螯合剂，用于68 Ga和64 Cu标记。通过固相肽合成法合成缀合物，通过反相高效液相色谱法纯化缀合物，并通过液相色谱质谱法验证缀合物。用B16 F10黑素瘤细胞的饱和和竞争性结合测定确定了化合物对VLA-4的亲和力。在小鼠B16 F10皮下荷瘤C57 BL/6小鼠中评价LLP 2A缀合物的生物分布。心内注射B16 F10细胞诱导黑色素瘤转移。在注射64 Cu示踪剂后2、4和24 h以及注射68 Ga示踪剂后1 h进行PET/CT成像。64 Cu标记的CB-TE 1A 1 P-PEG 4-LLP 2A和NODAGA-PEG 4-LLP 2A显示出对VLA-4的高亲和力，具有相当的解离常数（0.28 vs. 0.23 nM）和受体浓度（296 vs. 243 fmol/mg）。注射后2小时的肿瘤摄取对于2种探针是相当的，但是64 Cu-CB-TE 1A 1 P-PEG 4-LLP 2A倾向于比64 Cu-NODAGA-PEG 4-LLP 2A更高的摄取（16.9 ± 2.2相对于13.4 ± 1.7百分比注射剂量/克，P = 0.07）。来自生物分布和PET/CT图像的肿瘤与肌肉和肿瘤与血液的比率对于64 Cu-CB-TE 1A 1 P-PEG 4-LLP 2A显著高于64 Cu-NODAGA-PEG 4-LLP 2A（所有P值< 0.05）。用68 Ga-NODAGA-PEG 4-LLP 2A和64 Cu-NODAGA-PEG 4-LLP 2A进行的转移性黑色素瘤的PET/CT成像显示在转移部位的探针的高摄取，与肿瘤的生物发光成像相关。这些数据表明，64 Cu标记的CB-TE 1A 1 P/NODAGA LLP 2A缀合物和68 Ga标记的NODAGA-LLP 2A是用于黑色素瘤和潜在的其他VLA-4阳性肿瘤的优异的成像剂。64 Cu-CB-TE 1A 1 P-PEG 4-LLP 2A作为黑色素瘤的PET成像剂，具有最佳的肿瘤与非靶组织比率。
Melanoma is a malignant tumor derived from epidermal melanocytes, and it is known for its aggressiveness, therapeutic resistance, and predisposition for late metastasis. Very late antigen-4 (VLA-4; also called integrin α4β1) is a transmembrane noncovalent heterodimer overexpressed in melanoma tumors that plays an important role in tumor growth, angiogenesis, and metastasis by promoting adhesion and migration of cancer cells. In this study, we evaluated 2 conjugates of a high-affinity VLA-4 peptidomimetic ligand, LLP2A, for PET/CT imaging in a subcutaneous and metastatic melanoma tumor. LLP2A was conjugated to 1,4,8,11-tetraazacyclotetradecane-1-(methane phosphonic acid)-8-(methane carboxylic acid) (CB-TE1A1P) and 2-(4,7-bis(carboxymethyl)-1,4,7-triazonan-1-yl)pentanedioic acid (NODAGA) chelators for 68Ga and 64Cu labeling. The conjugates were synthesized by solid-phase peptide synthesis, purified by reversed-phase high-performance liquid chromatography, and verified by liquid chromatography mass spectrometry. Saturation and competitive binding assays with B16F10 melanoma cells determined the affinity of the compounds for VLA-4. The biodistributions of the LLP2A conjugates were evaluated in murine B16F10 subcutaneous tumor–bearing C57BL/6 mice. Melanoma metastasis was induced by intracardiac injection of B16F10 cells. PET/CT imaging was performed at 2, 4, and 24 h after injection for the 64Cu tracers and 1 h after injection for the 68Ga tracer. 64Cu-labeled CB-TE1A1P-PEG4-LLP2A and NODAGA-PEG4-LLP2A showed high affinity to VLA-4, with a comparable dissociation constant (0.28 vs. 0.23 nM) and receptor concentration (296 vs. 243 fmol/mg). The tumor uptake at 2 h after injection was comparable for the 2 probes, but 64Cu-CB-TE1A1P-PEG4-LLP2A trended toward higher uptake than 64Cu-NODAGA-PEG4-LLP2A (16.9 ± 2.2 vs. 13.4 ± 1.7 percentage injected dose per gram, P = 0.07). Tumor-to-muscle and tumor-to-blood ratios from biodistribution and PET/CT images were significantly higher for 64Cu-CB-TE1A1P-PEG4-LLP2A than 64Cu-NODAGA-PEG4-LLP2A (all P values < 0.05). PET/CT imaging of metastatic melanoma with 68Ga-NODAGA-PEG4-LLP2A and 64Cu-NODAGA-PEG4-LLP2A showed high uptake of the probes at the site of metastasis, correlating with the bioluminescence imaging of the tumor. These data demonstrate that 64Cu-labeled CB-TE1A1P/NODAGA LLP2A conjugates and 68Ga-labeled NODAGA-LLP2A are excellent imaging agents for melanoma and potentially other VLA-4–positive tumors. 64Cu-CB-TE1A1P-PEG4-LLP2A had the most optimal tumor–to–nontarget tissue ratios for translation into humans as a PET imaging agent for melanoma.