A Phage Display-Identified Peptide Selectively Binds to Kidney Injury Molecule-1 (KIM-1) and Detects KIM-1-Overexpressing Tumors In Vivo

Purpose This study was carried out to identify a peptide that selectively binds to kidney injury molecule-1 (KIM-1) by screening a phage-displayed peptide library and to use the peptide for the detection of KIM-1-overexpressing tumors in vivo. Materials and Methods Biopanning of a phage-displayed peptide library was performed on KIM-1-coated plates. The binding of phage clones, peptides, and a peptide multimer to the KIM-1 protein and KIM-1-overexpressing and KIM-1-low expressing cells was examined by enzyme-linked immunosorbent assay, fluorometry, and flow cytometry. A biotin-peptide multimer was generated using NeutrAvidin. In vivo homing of the peptide to KIM-1-overexpressing and KIM-1-low expressing tumors in mice was examined by whole-body fluorescence imaging. Results A phage clone displaying the CNWMINKEC peptide showed higher binding affinity to KIM-1 and KIM-1-overexpressing 769-P renal tumor cells compared to other phage clones selected after biopanning. The CNWMINKEC peptide and a NeutrAvidin/biotin-CNWMINKEC multimer selectively bound to KIM-1 over albumin and to KIM-1-overexpressing 769-P cells and A549 lung tumor cells compared to KIM-1-low expressing HEK293 normal cells. Co-localization and competition assays using an anti-KIM-1 antibody demonstrated that the binding of the CNWMINKEC peptide to 769-P cells was specifically mediated by KIM-1. The CNWMINKEC peptide was not cytotoxic to cells and was stable for up to 24 hours in the presence of serum. Whole-body fluorescence imaging demonstrated selective homing of the CNWM-INKEC peptide to KIM-1-overexpressing A498 renal tumor compared to KIM-1-low expressing HepG2 liver tumor in mice. Conclusion The CNWMINKEC peptide is a promising probe for in vivo imaging and detection of KIM-1-overexpressing tumors.