Tumor‐homing peptide and its utility for advanced cancer medicine

Cell‐penetrating peptides, such as 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 30 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 alternatively 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 (eg, with dye‐conjugated probes for direct visualization of invasive/metastatic tumor lesions in vivo) and therapeutics (eg, 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.