Small-Animal PET of Melanocortin 1 Receptor Expression Using a 18F-Labeled α-Melanocyte-Stimulating Hormone Analog

Journal of Nuclear Medicine

Mangal Dandekar¹  Lan Zhang¹  Edward Graves¹  Zhengming Xiong¹  Sanjiv Sam Gambhir¹  Xiaoyuan Chen¹  Zhen Cheng¹ 

关键词: melanoma;    α-melanocyte-stimulating hormone;    PET;    imaging;    ¹⁸F;   

DOI  :  10.2967/jnumed.107.039602

学科分类：医学（综合）

来源: Society of Nuclear Medicine

【 摘 要 】

18F-Labeled small synthetic peptides have emerged as attractive probes for imaging various molecular targets with PET. The α-melanocyte-stimulating hormone (α-MSH) receptor (melanocortin type 1 receptor [MC1R]) is overexpressed in most murine and human melanomas. It is a promising molecular target for diagnosis and therapy of melanomas. However, 18F compounds have not been successfully developed for imaging the MC1R. Methods: In this study, an α-MSH analog, Ac-Nle-Asp-His-d-Phe-Arg-Trp-Gly-Lys-NH2 (NAPamide), was radiolabeled with N-succinimidyl-4-18F-fluorobenzoate (18F-SFB). The resulting radiopeptide was evaluated as a potential molecular probe for small-animal PET of melanoma and MC1R expression in melanoma xenografted mouse models. Results: The binding affinity of 19F-SFB−conjugated NAPamide, 19F-FB-NAPamide, was determined to be 7.2 ± 1.2 nM (mean ± SD) using B16/F10 cells and 125I-(Tyr2)-[Nle4,d-Phe7]-α-MSH [125I-(Tyr2)-NDP] as a radioligand. The biodistribution of 18F-FB-NAPamide was then investigated in C57BL/6 mice bearing subcutaneous murine B16/F10 melanoma tumors with high expression of MC1Rs and Fox Chase Scid mice bearing human A375M melanoma with a relatively low number of MC1R receptors. Biodistribution experiments showed that tumor uptake values (percentage injected dose per gram of tumor [%ID/g]) of 18F-FB-NAPamide were 1.19 ± 0.11 %ID/g and 0.46 ± 0.11 %ID/g, in B16/F10 and A375M xenografted melanoma at 1 h after injection, respectively. Furthermore, the B16/F10 tumor uptake was significantly inhibited by coinjection with excess α-MSH peptide (P < 0.05), indicating that 18F-FB-NAPamide specifically recognizes the MC1R in living mice. Small-animal PET of 18F-FB-NAPamide in mice bearing B16/F10 and A375M tumors at 1 h after tail vein injection revealed good B16/F10 tumor-to-background contrast and low A375M tumor-to-background ratios. Conclusion: 18F-FB-NAPamide is a promising molecular probe for α-MSH receptor-positive melanoma PET and warrants further study.

【 授权许可】

Unknown