GRPR and cancer: The use of carrier peptidesfor targeted drug delivery has been shown to be effective in prostatecancer, where a high percentage of primary tumors and bone metastaseshave been found to overexpress the gastrin-releasing peptide receptor(GRPR).25−28 GRPR is also overexpressed in other human cancers, including breast,colorectal, lung, or pancreatic, while it is poorly expressed in healthytissues, making it an attractive target for selective cancer treatment.29,30,31