首页 | 本学科首页   官方微博 | 高级检索  
   检索      


Dimeric DOTA-alpha-melanocyte-stimulating hormone analogs: synthesis and in vivo characteristics of radiopeptides with high in vitro activity
Authors:Bapst Jean-Philippe  Froidevaux Sylvie  Calame Martine  Tanner Heidi  Eberle Alex N
Institution:Laboratory of Endocrinology, Department of Research, University Hospital and University Children's Hospital, Basel, Switzerland.
Abstract:Dimeric analogs of alpha-melanocyte-stimulating hormone (alpha-MSH) labeled with radiometals are potential candidates for diagnosis and therapy of melanoma by receptor-mediated tumor targeting. Both melanotic and amelanotic melanomas (over-)express the melanocortin-1 receptor (MC1-R), the target for alpha-MSH. In the past, dimerized MSH analogs have been shown to display increased receptor affinity compared to monomeric MSH, offering the possibility of improving the ratio between specific uptake of radiolabeled alpha-MSH by melanoma and nonspecific uptake by the kidneys. We have designed three linear dimeric analogs containing a slightly modified MSH hexapeptide core sequence (Nle-Asp-His-d-Phe-Arg-Trp) in parallel or antiparallel orientation, a short spacer, and the DOTA chelator for incorporation of the radiometal. In vitro, all three peptides were more potent ligands of the mouse B16-F1 melanoma cell melanocortin-1 receptor (MC1-R) than DOTA-NAPamide, which served as standard. The binding activity of DOTA-diHexa(NC-NC)-amide was 1.75-fold higher, that of diHexa(NC-NC)-Gly-Lys(DOTA)-amide was 3.37-fold higher, and that of DOTA-diHexa(CN-NC)-amide was 2.34-fold higher. Using human HBL melanoma cells, the binding activity of diHexa(NC-NC)-Gly-Lys(DOTA)-amide was sixfold higher than that of DOTA-NAPamide. Uptake by cultured B16-F1 cells was rapid and almost quantitative. In vivo, however, the data were less promising: tumor-to-kidney ratios 4 hr postinjection were 0.11 for (111)In]DOTA-diHexa(NC-NC)-amide, 0.26 for diHexa(NC-NC)-Gly-Lys((111)In]DOTA)-amide, and 0.36 for (111)In]DOTA-diHexa(CN-NC)-amide, compared to 1.67 for (111)In]DOTA-NAPamide. It appears that despite the higher affinity to the MC1-R of the peptide dimers and their excellent internalization in vitro, the uptake by melanoma tumors in vivo was lower, possibly because of reduced tissue penetration. More striking, however, was the marked increase of kidney uptake of the dimers, explaining the unfavorable ratios. In conclusion, although radiolabeled alpha-MSH dimer peptides display excellent receptor affinity and internalization, they are no alternative to the monomeric DOTA-NAPamide for in vivo application.
Keywords:
本文献已被 PubMed 等数据库收录!
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号