GRPR and prostate carcinoma: As summarized in Table 1, N4-GRP(14–27) showed high affinity for the GRPR expressed in resected prostate carcinoma specimens (IC50 = 4.2 ± 1.0 nM, n = 3, vs. IC50 = 2.4 ± 1.0 nM, n = 3 for N4-GRP(18–27) [23]), very low affinity for NMBR present in ileal carcinoid biopsy samples (IC50 = 72 ± 7.6 nM, n = 3, vs. IC50 = 106 ± 13 nM; n = 2 for N4-GRP(18–27) [23]), and no affinity for the BB3R expressed in bronchial carcinoid samples (IC50 > 1000 nM, n = 3, identical to N4-GRP(18–27) [23]).