Peptides containing the RGD (Arg–Gly–Asp) motif, which specifically bind to integrins, and those with the NGR (Asn–Gly–Arg) motif, which selectively target APN, are classified as tumor-homing peptides.56 In this context, the primary significance of APN in cancer diagnosis and therapy lies in its role as a target molecule for NGR peptides conjugated with various compounds—either as diagnostic probes for imaging tumor neovasculature or as carriers of antineoplastic agents. The gene discussed is RTN4R; the disease is cancer.