Noninvasive imaging and expression profile of matrix metalloproteinases in inflammation-induced colon cancer

Objectives Increased expression of matrix metalloproteinases (MMPs) in colon cancer accelerates primary tumor growth and possibly contributes to tumorigenesis. The purpose of this study is to characterize and image MMP expression with a near-infrared fluorescent (NIRF) cyclic His-Try-Gly-Phe peptide in a mouse model of inflammation-induced colon cancer.

Methods c(KAHWGFTLD)NH2 (C6) peptide to target MMPs was prepared from standard Fmoc peptide synthesis. Cy5.5 was conjugated to C6 peptide for NIRF imaging and Cy5.5-C6 was purified by preparative RP-HPLC. To develop a mouse model for inflammation-related colon cancer, mice (female, 6 week-old) were given a single intraperitoneal administration (10 mg/kg body weight) of azoxymethane (AOM) and a 1-week oral exposure to 2% dextran sodium sulfate (DSS). In vivo MMP-targeted imaging of Cy5.5-C6 was accessed using an IVIS optical imaging system in a colon cancer model. MMP expression and beta-catenin activation in the colon cancer of the mouse model was characterized by immunohistochemical staining.

Results Molecular weight of Cy5.5-C6 determined by maldi-tof-ms analysis was 1954.78 (calculated MW = 1955.23). In the inflammation-induced colon cancer model, histological examination of the cancer tissues revealed high MMP expression. Identification of MMP expression profiles correlated to beta-catenin activation in the colon lesions. The in vitro characterization of Cy5.5-C6 exhibited MMP binding specificity in a cell experiment. In vivo NIRF imaging showed high tumor accumulation of Cy5.5-C6 with correlation to MMP expression in the colon lesions after intravenous injection. The MMP specificity of Cy5.5-C6 was confirmed by successful inhibition of tumor uptake in the presence of excess C6 peptide.

Conclusions The inflammation-induced colon cancer showed increased MMP expression and beta-catenin activation. Cy5.5-C6 has the potential to be developed into an effective molecular imaging agent to monitor MMP expression in colon cancer