Investigation of a MMP-2 activity-dependent anchoring probe for nuclear imaging of cancer

Abstract

Purpose: Since matrix metalloproteinase-2 (MMP-2) is an important marker of tumor malignancy, we developed an original drug design strategy, MMP-2 activity dependent anchoring probes (MDAP), for use in MMP-2 activity imaging, and evaluated the usefulness of this probe in in vitro and in vivo experiments. Methods: We designed and synthesized MDAP 1000, MDAP 3000, and MDAP 5000, which consist of 4 independent moieties: RI unit ( 111 In hydrophilic chelate), MMP-2 substrate unit (short peptide), anchoring unit (alkyl chain), and anchoring inhibition unit (polyethylene glycol (PEGn; where n represents the approximate molecular weight, n = 1000, 3000, and 5000). Probe cleavage was evaluated by chromatography after MMP-2 treatment. Cellular uptake of the probes was then measured. Radioactivity accumulation in tumor xenografts was evaluated after intravenous injection of the probes, and probe cleavage was evaluated in tumor homogenates. Results: MDAP 1000, MDAP 3000, and MDAP 5000 were cleaved by MMP-2 in a concentration-dependent manner. MDAP 3000 pretreated with MMP-2 showed higher accumulation in tumor cells, and was completely blocked by additional treatment with an MMP inhibitor. MDAP 3000 exhibited rapid blood clearance and a high tumor accumulation after intravenous injection in a rodent model. Furthermore, pharmacokinetic analysis revealed that MDAP 3000 exhibited a considerably slow washout rate from tumors to blood. A certain fraction of cleaved MDAP 3000 existed in tumor xenografts in vivo. Conclusions: The results indicate the possible usefulness of our MDAP strategy for tumor imaging. © 2014 Temma et al.