Correlation between Properties of pHLIP Peptide-Lipid Interaction and Tumor Targeting In Vivo

Abstract

We have discovered a way to target acidity in vivo, which is a hallmark of many pathological states. The tumor targeting is based on the pH-dependent transmembrane insertion and folding of the water-soluble membrane peptide, pHLIP - pH (Low) Insertion Peptide. Here we present the result of the sequence variation study of pHLIP, which was carried out with the main goal to improve blood clearance and tumor targeting at low pH. We have investigated more than 10 pHLIP variants with various mutations in transmembrane and C-terminal parts, including peptides with significantly truncated transmembrane part. Currently our library of pHLIP variants, contains peptides inserting into bilayer with pKa ranging from 4.5 to 6.5, which have different affinity to lipid bilayer at neutral and low pHs. Kinetics measurements indicate that all investigated variants containing truncated or no C-terminal flanking sequence demonstrate fast insertion into lipid bilayer. The results of biophysical studies are in excellent agreement with the tumor targeting and blood clearance data obtained in vivo. Our data contribute in understanding of main principles of peptide-lipid interactions.