RT Journal Article
SR Electronic
T1 Identification of Bombesin Receptor Subtype-Specific Ligands: Effect of <em>N</em>-Methyl Scanning, Truncation, Substitution, and Evaluation of Putative Reported Selective Ligands
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 980
OP 989
DO 10.1124/jpet.106.107011
VO 319
IS 2
A1 Mantey, Samuel A.
A1 Gonzalez, Nieves
A1 Schumann, Michael
A1 Pradhan, Tapas K.
A1 Shen, Lin
A1 Coy, David H.
A1 Jensen, Robert T.
YR 2006
UL http://jpet.aspetjournals.org/content/319/2/980.abstract
AB Mammalian bombesin (Bn) receptors include the gastrin-releasing peptide receptor, neuromedin B receptor, and bombesin receptor subtype 3 (BRS-3). These receptors are involved in a variety of physiological/pathologic processes, including thermoregulation, secretion, motility, chemotaxis, and mitogenic effects on both normal and malignant cells. Tumors frequently overexpress these receptors, and their presence is now used for imaging and receptor-mediated cytotoxicity. For these reasons, there is an increased need to develop synthetic, selective receptor subtype-specific ligands, especially agonists for these receptors. In this study, we used a number of strategies to identify useful receptor subtype-selective ligands, including synthesizing new analogs (N-methyl-substituted constrained analogs, truncations, and substitutions) in [d-Tyr6,βAla11,Phe13,Nle14]Bn(6–14), which has high affinity for all Bn receptors and is metabolically stable, as well as completely pharmacologically characterized analogs recently reported to be selective for these receptors in [Ca2+]i assays. Affinities and potencies of each analog were determined for each human Bn receptor subtype. N-Methyl substitutions in positions 14, 12, 11, 10, 9, and 8 did not result in selective analogs, with the exception of position 11, which markedly decreased affinity/potency. N-Terminal truncations or position 12 substitutions did not increase selectivity as previously reported by others. Of the four shortened analogs of [d-Phe6,βAla11,Phe13,Nle14]Bn(6–14) reported to be potent selective BRS-3 ligands on [Ca2+]i assays, only AcPhe,Trp,Ala,His(τBzl),Nip,Gly,Arg-NH2 had moderate selectivity for hBRS-3; however, it was less selective than previously reported Apa11 analogs, demonstrating these are still the most selective BRS-3 analogs available. However, both of these analogs should be useful templates to develop more selective BRS-3 ligands. The American Society for Pharmacology and Experimental Therapeutics