Design of radiolabeled gelatinase inhibitor peptide (99mTc-CLP) and evaluation in rats

In malignant tissues, MMP-9 (gelatinase B, 92 kDa type IV collagenase) and MMP-2 (gelatinase A, 72 kDa type IV collagenase) are the most prevalent matrix metalloproteinases related to the tumor aggressiveness and metastatic potential. Since elevated levels of gelatinases are associated with poor prognosis in cancer patients, these enzymes are potential targets for tumor imaging to possibly predict metastases. In the present study, a cyclic decapeptide, CLP (Cys-Leu-Pro-Gly-His-Trp-Gly-Phe-Pro-Ser-Cys), was selected as a basic peptide because of its selective inhibitory activity toward gelatinases. The peptide was labelled with 99mTc with a radiolabelling efficiency of 94.6±4.1%. After determining the appropriate conditions for radiolabelling, a biodistribution study of radiolabelled peptide in Albino Wistar rats was done. According to biodistribution data, 99mTc-CLP showed high uptake in the lung, liver, uterus and spleen. The amount of normal tissue MMPs enzymes is known to be lower than a tumor tissue. In this connection, our findings show that matrix metalloproteinases inhibitory peptide which is CLP is labeled with 99mTc with high yield and radiolabeled peptide might be might be utilized for the imaging of gelatinase activity due to overexpression of MMP-2 and MMP-9 in tumor tissue.