From a theranostic perspective, for tumor scanning and, more recently, for peptide receptor radiotherapy treatment of tumors, radiolabeled peptides such as neurotensin, substance P, gastrin-releasing peptide, glucagon-like peptide 1, and neuropeptide Y (NPY) have been studied for targeting breast, prostate, ovarian, pancreatic, and brain cancers [91]. The gene discussed is NPY; the disease is brain cancer.