Abstract
A peptide targeted contrast agent, CLT1-(Gd-DTPA), was investigated for molecular imaging of fibrin-fibronectin complexes in tumor stroma with magnetic resonance imaging (MRI). The contrast agent was evaluated in female nude mice bearing MDA-MB-231 human breast carcinoma xenografts on a Siemens 3T clinical scanner with a clinical agent Gd(DTPA-BMA) as a non-targeted control. CLT1-(Gd-DTPA) specifically bound to tumor tissue and resulted in significant tumor contrast enhancement at a dose of 0.05 mmol/kg for at least 60 minutes after injection. In contrast, a non-targeted contrast agent, Gd(DTPA-BMA), cleared rapidly from the body with little tumor enhancement after 30 minutes post-injection at a dose of 0.1 mmol/kg. CLT1-(Gd-DTPA) had little non-specific binding in blood and normal tissues, including the liver and muscle, resulting in comparable non-specific enhancement in normal tissues as the control agent. The study has shown that CLT1-(Gd-DTPA) can bind to the tumor tissue, resulting in significant tumor enhancement in a mouse breast cancer model. The targeted contrast agent has a potential for MR molecular imaging of breast cancer.