Substitution of Gly with Ala enhanced the melanoma uptake of technetium-99m-labeled Arg-Ala-Asp-conjugated alpha-melanocyte stimulating hormone peptide

The purpose of this study was to determine the melanoma targeting property of ^99mTc-RAD-Lys- (Arg¹¹)CCMSH in B16/F1 melanoma-bearing C57 mice and compare with ^99mTc-RGD-Lys-(Arg¹¹)CCMSH we previously reported. ^99mTc-RAD-Lys-(Arg¹¹)CCMSH exhibited rapid and high tumor uptake (19.91 ± 4.02% ID/g at 2 h post-injection) in B16/F1 melanoma-bearing C57 mice. The tumor uptake of ^99mTc-RAD-Lys- (Arg¹¹)CCMSH was 1.51, 1.34 and 1.43 times the tumor uptake of ^99mTc-RGD-Lys- (Arg¹¹)CCMSH at 0.5, 2 and 4 h post-injection, respectively. Flank B16/F1 melanoma lesions were clearly imaged at 2 h post-injection using ^99mTc-RAD-Lys-(Arg¹¹)CCMSH as an imaging probe. The substitution of Gly with Ala significantly enhanced the melanoma uptake of ^99mTc-RAD-Lys-(Arg¹¹)CCMSH compared to ^99mTc-RGD-Lys-(Arg¹¹)CCMSH in B16/F1 melanoma-bearing C57 mice, providing a new insight into the design of a-MSH peptides for melanoma targeting.