The currently available anticancer agents frequently cause unwanted normal cell death mainly owing to their lack of selectivity for cancer cells. In addition, molecular imaging agents for tumors exhibit low target-to-background ratios. As a consequence, elegant methods that more specifically target cancer cells need to be developed for the improvement of chemotherapeutic efficacy and diagnosis. In a recent effort aimed at improving the tumor selectivity of therapeutic and imaging agents, we designed, synthesized and explored the effectiveness of a dual-targeting delivery system that targets cancer cells more selectively. The new delivery system is composed of a synthetic ligand (octreotide) of somatostatin receptors, a dipeptide substrate for cathepsin B, and a fluorophore or an anticancer agent. The fluorophore-conjugated delivery system was found to be applicable for specific fluorescence imaging of cancer cells that express both somatostatin receptors and cathepsin B. In addition, the anticancer agent-containing delivery system leads to the death of cancer cells specifically. In contrast to cancer cells, normal cells that do not produce both somatostatin receptors and cathepsin B at high levels are unaffected by the delivery system. The new dual-targeting approach has the capability of overcoming obstacles associated with current chemotherapeutic and imaging methods.
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