RTN4R and neoplasm: RGD‐containing peptides have been widely used in tumor‐targeting research.25 Peptides containing the Asn‐Gly‐Arg (NGR) motif which can recognize aminopeptidase N (CD13), a membrane‐bound enzyme associated with angiogenic tumor vessels, can be used for delivering various anti‐tumor agents to the tumor vasculature.26 Based on this, RGD‐ and NGR‐containing peptides can actively target to tumor blood vessels by binding to integrin and CD13 receptors.