Replacement of the Lys linker with an Arg linker resulting in improved melanoma uptake and reduced renal uptake of Tc-99m-labeled Arg-Gly-Asp-conjugated alpha-melanocyte stimulating hormone hybrid peptide

Abstract

The purpose of this study was to reduce the non-specific renal uptake of Arg-Gly-Asp (RGD)-conjugated alpha-melanocyte stimulating hormone (α-MSH) hybrid peptide through structural modification or L-lysine co-injection. The RGD motif {cyclic(Arg-Gly-Asp-DTyr-Asp)} was coupled to [Cys 3,4,10 , D-Phe 7 , Arg 11 ]α-MSH 3-13 {(Arg 11 )CCMSH} through the Arg linker (substituting the Lys linker) to generate a novel RGD-Arg-(Arg 11 )CCMSH hybrid peptide. The melanoma targeting and pharmacokinetic properties of 99m Tc-RGD-Arg-(Arg 11 )CCMSH were determined in B16/F1 melanoma-bearing C57 mice. The effect of L-lysine co-injection on the renal uptake was determined through the co-injection of L-lysine with 99m Tc-RGD-Arg-(Arg 11 )CCMSH or 99m Tc-RGD-Lys-(Arg 11 )CCMSH. Replacement of the Lys linker with an Arg linker exhibited a profound effect in reducing the non-specific renal uptake of 99m Tc-RGD-Arg-(Arg 11 )CCMSH, as well as increasing the tumor uptake of 99m Tc-RGD-Arg-(Arg 11 )CCMSH compared to 99m Tc-RGD-Lys-(Arg 11 )CCMSH. 99m Tc-RGD-Arg-(Arg 11 )CCMSH exhibited high tumor uptake (21.41 ± 3.74% ID/g at 2 h post-injection) and prolonged tumor retention (6.81 ± 3.71% ID/g at 24 h post-injection) in B16/F1 melanoma-bearing mice. The renal uptake values of 99m Tc-RGD-Arg-(Arg 11 )CCMSH were 40.14-64.08% of those of 99m Tc-RGD-Lys-(Arg 11 )CCMSH (p<0.05) at 0.5, 2, 4 and 24 h post-injection. Co-injection of L-lysine was effective in decreasing the renal uptakes of 99m Tc-RGD-Arg-(Arg 11 )CCMSH by 27.7% and 99m Tc-RGD-Lys-(Arg 11 )CCMSH by 52.1% at 2 h post-injection. Substitution of the Lys linker with an Arg linker dramatically improved the melanoma uptake and reduced the renal uptake of 99m Tc-RGD-Arg-(Arg 11 )CCMSH, warranting the further evaluation of 188 Re-labeled RGD-Arg-(Arg 11 )CCMSH as a novel MC1 receptor-targeting therapeutic peptide for melanoma treatment in the future.

Tc-99m-labeled RGD-conjugated alpha-melanocyte stimulating hormone hybrid peptides with reduced renal uptake

“…Specifically, three –SH groups from Cys 3 , Cys 4 and Cys 10 and one –NH group from Cys 4 form a NS 3 chelating system for 99m Tc. 99m Tc-RGD-Arg-(Arg 11 )CCMSH exhibited more favorable pharmacokinetic properties than 99m Tc-RGD-Lys-(Arg 11 )CCMSH in our previous report (Yang et al 2010). Specifically, 99m Tc-RGD-Arg-(Arg 11 )CCMSH displayed 44% higher tumor uptake and 33% less renal uptake than 99m Tc-RGD-Lys-(Arg 11 )CCMSH at 2 h post-injection (Yang et al 2010).…”

“…Novel and effective treatments are urgently needed to fulfill the desperate need for melanoma treatment since no curative treatment exists for metastatic melanoma. Recently, we have utilized the MC1 receptor-targeting (Arg 11 )CCMSH peptide as a delivery vehicle to transport the RGD motif into melanoma cells to induce apoptosis (Yang et al 2009, 2010). Both RGD-Lys-(Arg 11 )CCMSH and RGD-Arg-(Arg 11 )CCMSH exhibited remarkable growth inhibition in B16/F1 melanoma cells.…”

“…The structures of RGD-Lys-(Arg 11 )CCMSH and RGD-Arg-(Arg 11 )CCMSH were cited from the references (Yang et al 2009, 2010) for comparison.…”

“…RGD-Arg-(Arg 11 )CCMSH displayed similar remarkable clonogenic cytotoxic effect as RGD-Lys-(Arg 11 )CCMSH in B16/F1 melanoma cells (Yang et al 2010). Importantly, co-injection of 15 mg of L -lysine substantially decreased the renal uptake of 99m Tc-RGD-Lys-(Arg 11 )CCMSH by 52% and the renal uptake of 99m Tc-RGD-Arg-(Arg 11 )CCMSH by 28% at 2 h post-injection, indicating that the overall positive charges of 99m Tc-RGD-Lys-(Arg 11 )CCMSH and 99m Tc-RGD-Arg-(Arg 11 )CCMSH contributed to their non-specific renal uptake (Yang et al 2010).…”

“…Thus, both linear and cyclic alpha-melanocyte stimulating hormone (α-MSH) peptide radiopharmaceuticals have been reported to target the MC1 receptors for melanoma detection and treatment (Chen et al 2001; Cheng et al 2002, 2007; Froidevaux et al 2002, 2004, 2005; Guo et al 2009, 2009, 2010; Miao et al 2002, 2005, 2005, 2007, 2008; Wei et al 2007). Recently, we have reported a novel class of Arg-Gly-Asp-conjugated α-MSH hybrid peptides targeting the MC1 receptors for potential melanoma imaging and therapy (Yang et al 2009, 2010). The RGD motif {cyclic(Arg-Gly-Asp- D Tyr-Asp)} was used as an apoptosis inducer and was conjugated to the [Cys 3,4,10 , D-Phe 7 , Arg 11 ]α-MSH 3–13 {(Arg 11 )CCMSH} peptide through a Lys linker to yield RGD-Lys-(Arg 11 )CCMSH hybrid peptide (Yang et al 2009).…”