VIPR1 and urinary bladder cancer: Extensive literature reports the application of peptides that specifically bind to different types of cells, such as tumor blood vessels, tumor lymphatic vessels, tumor cells, or to specific cell surface receptors, such as integrin and neuropilin, nestin, VPAC1 receptor, FGF9 in gastric and bladder cancer, or CD133 in glioblastoma (27–33).