Evaluation of a novel Arg-Gly-Asp-conjugated α-melanocyte stimulating hormone hybrid peptide for potential melanoma therapy.
The purpose of this study was to determine whether Arg-Gly-Asp (RGD)-conjugated α-melanocyte stimulating hormone (α-MSH) hybrid peptide could be employed to target melanocortin-1 (MC1) receptor for potential melanoma therapy.


METHODS
The RGD motif {cyclic(Arg-Gly-Asp-DTyr-Asp)} was coupled to [Cys(3,4,10), DPhe(7), Arg(11)]α-MSH(3-13) {(Arg(11))CCMSH} to generate RGD-Lys-(Arg(11))CCMSH hybrid peptide. The MC1 receptor binding affinity of RGD-Lys-(Arg(11))CCMSH was determined in B16/F1 melanoma cells. The internalization and efflux, melanoma targeting and pharmacokinetic properties and single photon emission computed tomography/CT (SPECT/CT) imaging of (99m)Tc-RGD-Lys-(Arg(11))CCMSH were determined in B16/F1 melanoma cells and melanoma-bearing C57 mice. Clonogenic cytotoxic effect of RGD-Lys-(Arg(11))CCMSH was examined in B16/F1 melanoma cells.


RESULTS
RGD-Lys-(Arg(11))CCMSH displayed 2.1 nM MC1 receptor binding affinity. (99m)Tc-RGD-Lys-(Arg(11))CCMSH showed rapid internalization and extended retention in B16/F1 cells. The cellular uptake of (99m)Tc-RGD-Lys-(Arg(11))CCMSH was MC1 receptor-mediated. (99m)Tc-RGD-Lys-(Arg(11))CCMSH exhibited high tumor uptake (14.83 ± 2.94% ID/g 2 h postinjection) and prolonged tumor retention (7.59 ± 2.04% ID/g 24 h postinjection) in B16/F1 melanoma-bearing mice. Nontarget organ uptakes were generally low except for the kidneys. Whole-body clearance of (99m)Tc-RGD-Lys-(Arg(11))CCMSH was rapid, with approximately 62% of the injected radioactivity cleared through the urinary system by 2 h postinjection. Flank melanoma tumors were clearly imaged by small animal SPECT/CT using (99m)Tc-RGD-Lys-(Arg(11))CCMSH as an imaging probe 2 h postinjection. Single treatment (3 h incubation) with 100 nM of RGD-Lys-(Arg(11))CCMSH significantly (p < 0.05) decreased the clonogenic survival of B16/F1 cells by 65% compared to the untreated control cells.


CONCLUSIONS
Favorable melanoma targeting property of (99m)Tc-RGD-Lys-(Arg(11))CCMSH and remarkable cytotoxic effect of RGD-Lys-(Arg(11))CCMSH in B16/F1 cells warranted the further evaluation of (188)Re-labeled α-MSH hybrid peptides as novel therapeutic peptides for melanoma treatment once the strategies of amino acid coinjection or structural modification of peptide sequence substantially reduce the renal uptake.
Yang
Jianquan
J
College of Pharmacy, University of New Mexico, Albuquerque, New Mexico 87131-0001, USA.
Guo
Haixun
H
Gallazzi
Fabio
F
Berwick
Marianne
M
Padilla
R Steven
RS
Miao
Yubin
Y
D000818:Animals; D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology / Q000627:therapeutic use*; D002470:Cell Survival / Q000187:drug effects; D005260:Female; D008546:Melanoma, Experimental / Q000188:drug therapy*; D051379:Mice; D008810:Mice, Inbred C57BL; D009842:Oligopeptides / Q000737:chemistry*; D013329:Structure-Activity Relationship; D013667:Technetium / Q000737:chemistry; D014018:Tissue Distribution; D023041:Xenograft Model Antitumor Assays; D000521:alpha-MSH / Q000737:chemistry* / Q000494:pharmacology / Q000627:therapeutic use*
D000970:Antineoplastic Agents; D009842:Oligopeptides; D000521:alpha-MSH; D013667:Technetium; C047981:arginyl-glycyl-aspartic acid