64Cu-Labeled alpha-melanocyte-stimulating hormone analog for MicroPET imaging of melanocortin 1 receptor expression
64Cu-Labeled alpha-melanocyte-stimulating hormone analog for MicroPET imaging of melanocortin 1 receptor expression
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DOI：
10.1021/bc060306g
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发表时间：
2007-05-01
影响因子：
4.7
通讯作者：
Gambhir, Sanjiv Sam
中科院分区：
文献类型：
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作者：
Cheng, Zhen;Xiong, Zhengming;Gambhir, Sanjiv Sam
α-黑素细胞刺激激素（α-MSH）受体（黑皮质素1型受体，或MC 1 R）在黑色素瘤细胞的发育和生长中起重要作用。发现MC 1 R在大多数鼠和人黑素瘤上过表达，使其成为黑素瘤成像和治疗的有希望的分子靶标。放射性标记的α-MSH肽及其类似物可以与MC 1 R特异性结合，已被广泛探索用于开发用于黑色素瘤检测和放射性核素治疗的新型药物。本研究的目的是评价Cu-64标记的α-MSH类似物Ac-Nle-Asp-His-D-Phe-Arg-Trp-Gly-Lys（DOTA）-NH 2（DOTA-NAPamide）作为黑素瘤异种移植小鼠模型中黑素瘤和MC 1 R表达的microPET成像的潜在分子探针。合成1，4，7，10-四氮杂环十二烷-1，4，7，10-四乙酸（DOTA）缀合的NAP酰胺，并在50 ℃下用Cu-64（t（12）=12 h）在NH 40 Ac（0.1 M; pH 5.5）缓冲溶液中放射性标记60 min。细胞培养研究揭示了Cu-64-DOTA-NAPamide在B16 F10细胞中的快速和高摄取和内化。超过90%的受体结合示踪剂在3小时孵育时内化。细胞保留研究表明，受体结合的Cu-64-DOTA-NAPamide从B16 F10细胞缓慢释放到培养基中;即使在孵育3小时后，66%的放射性仍与细胞相关。然后在具有高MC 1 R能力的皮下鼠B16 F10黑素瘤肿瘤的C57 BL/6小鼠和具有相对低数量的MC 1 R受体的人A375 M黑素瘤的Fox Chase Scid小鼠中研究Cu-64-DOTA-NAPamide的生物分布。发现Cu-64-DOTA-NAPamide的肿瘤摄取值在注射后2小时（pi）在B16 F10和A375 M异种移植的黑素瘤中分别为4.63 +/-0.45%和2.49 +/-0.31%ID/g。共注射过量的α-MSH肽后，B16 F10肿瘤摄取在注射后2小时进一步抑制至2.29 +/-0.24%ID/g，而A375 M肿瘤摄取在注射后2小时保持为2.20 +/-0.41%ID/g。Cu-64-DOTA-NAPamide在B16 F10肿瘤小鼠中的MicroPET成像清楚地显示出良好的肿瘤定位。然而，观察到低的A375 M肿瘤摄取和差的肿瘤与正常组织对比。本研究表明，Cu-64-DOTA-NAPamide是一种有前途的分子探针，可用于活体小鼠中α-MSH受体阳性黑色素瘤PET成像以及MC 1 R表达成像。
The alpha-melanocyte-stimulating hormone (alpha-MSH) receptor (melanocortin type 1 receptor, or MC1R) plays an important role in the development and growth of melanoma cells. It was found that MC1R was overexpressed on most murine and human melanoma, making it a promising molecular target for melanoma imaging and therapy. Radiolabeled alpha-MSH peptide and its analogs that can specifically bind with MC1R have been extensively explored for developing novel agents for melanoma detection and radionuclide therapy. The goal of this study was to evaluate a Cu-64-labeled alpha-MSH analog, Ac-Nle-Asp-His-D-Phe-Arg-Trp-Gly-Lys(DOTA)-NH2 (DOTA-NAPamide), as a potential molecular probe for microPET imaging of melanoma and MC1R expression in melanoma xenografted mouse models. 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) conjugated NAPamide was synthesized and radiolabeled with Cu-64 (t(1/2)=12 h) in NH4OAc (0.1 M; pH 5.5) buffered solution for 60 min at 50 degrees C. Cell culture studies reveal rapid and high uptake and internalization of Cu-64-DOTA-NAPamide in B16F10 cells. Over 90% of receptor-bound tracer is internalized at 3 h incubation. A cellular retention study demonstrates that the receptor-bound Cu-64-DOTA-NAPamide is slowly released from the B16F10 cells into the medium; 66% of the radioactivity is still associated with the cells even after 3 h incubation. The biodistribution of Cu-64-DOTA-NAPamide was then investigated in C57BL/6 mice bearing subcutaneous murine B16F10 melanoma tumors with high capacity of MC1R and Fox Chase Scid mice bearing human A375M melanoma with a relatively low number of MC1R receptors. Tumor uptake values of Cu-64-DOTA-NAPamide are found to be 4.63 +/- 0.45% and 2.49 +/- 0.31% ID/g in B16F10 and A375M xenografted melanoma at 2 h postinjection (pi), respectively. The B16F10 tumor uptake at 2 h pi is further inhibited to 2.29 +/- 0.24% ID/g, while A375M tumor uptake at 2 h pi remains 2.20 +/- 0.41% ID/g with a coinjection of excess alpha-MSH peptide. MicroPET imaging of Cu-64-DOTA-NAPamide in B16F10 tumor mice clearly shows good tumor localization. However, low A375M tumor uptake and poor tumor to normal tissue contrast were observed. This study demonstrates that Cu-64-DOTA-NAPamide is a promising molecular probe for alpha-MSH receptor positive melanoma PET imaging as well as MC1R expression imaging in living mice.