Table 2.

Peptide receptors which have potential in cancer therapy.

Peptide receptors	Receptor subtypes	Expressing tumor type	Targeting agents
Somatostatin	sst1, sst2, sst3, sst4, and sst5	GH-producing pituitary adenoma, paraganglioma, nonfunctioning pituitary adenoma, pheochromocytomas	Radioisotopes, AN-201 (a potent cytotoxic radical 2-pyrrolinodoxorubicin), doxorubicin
Pituitary adenylate cyclase activating peptide (PACAP)	PAC1	Pheochromocytomas and paragangliomas	Radioisotopes, doxorubicin
Vasoactive intestinal peptide (VIP/PACAP)	VPAC1, VPAC2	Cancers of lung stomach, colon, rectum, breast, prostate, pancreatic ducts, liver, and urinary bladder	Radioisotopes, camptothecin
Cholecystokinin (CCK)	CCK1 (formerly CCK-A) and CCK2	Small cell lung cancers, medullary thyroid carcinomas, astrocytomas, and ovarian cancers	Radioisotopes, cisplatin
Bombesin/gastrin-releasing peptide (GRP)	BB1, GRP receptor subtype (BB2), the BB3 and BB4	Renal cell, breast, and prostate carcinomas	Doxorubicin, 2-pyrrolinodoxorubicin
Neurotensin	NTR1, NTR2, NTR3	Small cell lung cancer, neuroblastoma, pancreatic and colonic cancer	Radioisotopes
Substance P	NK1 receptor	Glial tumors	Radioisotopes
Neuropeptide Y	Y1–Y6	Breast carcinomas	Radioisotopes