Evaluation of tricine and EDDA as Co-ligands for 99mTc-labeled HYNIC-MSH analogs for melanoma imaging

Anticancer Agents Med Chem. 2015;15(1):122-30. doi: 10.2174/1871520614666140825123150.

Abstract

Several radiolabeled alpha-melanocyte stimulating hormone (α-MSH) analogs have been studied for their abilities to target melanoma tumor cells through specific recognition and binding to the melanocortin receptor 1 (MCR1). In this work, a lactam bridgecyclized α-MSH analog was labeled with (99m) via the hydrazinonicotinamide (HYNIC) chelator and characterized for its melanoma tumor targeting properties. The bifunctional chelating agent HYNIC-Boc was attached to the N-terminus of the MSH peptide followed by the lactam cyclization, resulting in the HYNIC-cyc-MSH analog. The lactam cyclized peptide displayed high affinity and specificity for MC1-receptors present on B16/F1 melanoma tumor cells, exhibiting an IC50 of 6.48 nM. HYNIC-cyc-MSH was radiolabeled with (99m)Tc using two common co-ligands, tricine and EDDA. In vitro, the radiochemical stability, cell binding and efflux properties were similar between the peptides radiolabeled with tricine and EDDA as co-ligands. In vivo, biodistribution studies (n=4) demonstrated that (99m)Tc- HYNIC-cyc-MSH/tricine had superior tumor to muscle and tumor to blood ratios than (99m)Tc-HYNIC-cyc-MSH/EDDA at early time points. Planar gamma imaging of melanoma bearing mice showed that 99mTc-HYNIC-cyc-MSH/tricine was able to clearly visualize tumors, underscoring the potential utility of (99m)Tc labeled lactam cyclized MSH molecules as melanoma imaging agents.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chelating Agents / chemistry
  • Diagnostic Imaging / methods
  • Edetic Acid / analogs & derivatives*
  • Edetic Acid / chemistry
  • Glycine / analogs & derivatives*
  • Glycine / chemistry
  • Hydrazines / chemistry*
  • Ligands
  • Melanoma, Experimental / diagnosis*
  • Mice
  • Mice, Inbred C57BL
  • Nicotinic Acids / chemistry*
  • Organotechnetium Compounds / chemistry*
  • Peptides / chemistry
  • Protein Binding
  • Radiopharmaceuticals / chemistry*
  • Tissue Distribution
  • alpha-MSH / chemistry*

Substances

  • 6-hydrazinopyridine-3-carboxylic acid
  • Chelating Agents
  • Hydrazines
  • Ligands
  • Nicotinic Acids
  • Organotechnetium Compounds
  • Peptides
  • Radiopharmaceuticals
  • EDDA
  • alpha-MSH
  • Edetic Acid
  • Glycine
  • tricine