Tumor‐homing peptide and its utility for advanced cancer medicine

Cell-penetrating peptides, like antibodies, have gained great attention as tools for the development of specific delivery systems for payloads, which might be applied as non-invasive carriers in vivo. Among these, tumor-homing peptides recently have been studied for use in tumor medicine. Tumor-homing peptides are oligopeptides, usually consisting of thirty or fewer amino acids, that are efficiently and specifically incorporated into tumor cells, suggesting their potential use in establishing novel non-invasive tumor imaging systems for diagnostic and therapeutic applications. Here, we briefly introduce the biological characteristics of our tumor-homing peptides, focusing especially on those developed using a random peptide library constructed using mRNA display technology. The advantage of the tumor-homing peptides is their biological safety, given that these molecules do not show significant cytotoxicity against non-neoplastic cells; lack serious antigenicity, which otherwise might evoke unfavorable immune responses and inflammation in vivo; and are rapidly incorporated into target cells/tissues, with rates exceeding those seen for antibodies. Given their small size, tumor-homing peptides also are easy to modify and redesign. Based on these merits, tumor-homing peptides are expected to find wide application in various aspects of tumor medicine, including imaging diagnostics (e.g., with dye-conjugated probes for direct visualization of invasive/metastatic tumor lesions in vivo) and therapeutics (e.g., using peptide-drug conjugates (PDCs) for tumor targeting). Although further evidence will be required to demonstrate their practical utility, tumor-homing peptides are expected to show great potential as a next-generation bio-tool contributing to precision medicine for cancer patients.