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Uehara H.,U.S. National Institutes of Health | Gonzalez N.,U.S. National Institutes of Health | Sancho V.,U.S. National Institutes of Health | Mantey S.A.,U.S. National Institutes of Health | And 4 more authors.
Peptides | Year: 2011

The mammalian bombesin (Bn)-receptor family [gastrin-releasing peptide-receptor (GRPR-receptor), neuromedin B-receptor (NMB receptor)], their natural ligands, GRP/NMB, as well as the related orphan receptor, BRS-3, are widely distributed, and frequently overexpressed by tumors. There is increased interest in agonists for this receptor family to explore their roles in physiological/pathophysiological processes, and for receptor-imaging/ cytotoxicity in tumors. However, there is minimal data on human pharmacology of Bn receptor agonists and most results are based on nonhuman receptor studies, particular rodent-receptors, which with other receptors frequently differ from human-receptors. To address this issue we compared hNMB-/GRP-receptor affinities and potencies/efficacies of cell activation (assessing phospholipase C activity) for 24 putative Bn-agonists (12 natural, 12 synthetic) in four different cells with these receptors, containing native receptors or receptors expressed at physiological densities, and compared the results to native rat GRP-receptor containing cells (AR42J-cells) or rat NMB receptor cells (C6-glioblastoma cells). There were close correlations (r = 0.92-99, p < 0.0001) between their affinities/potencies for the two hGRP- or hNMB-receptor cells. Twelve analogs had high affinities (≤1 nM) for hGRP receptor with 15 selective for it (greatest = GRP, NMC), eight had high affinity/potencies for hNMB receptors and four were selective for it. Only synthetic Bn analogs containing β-alanine 11 had high affinity for hBRS-3, but also had high affinities/potencies for all GRP-/hNMB-receptor cells. There was no correlation between affinities for human GRP receptors and rat GRP receptors (r = 0.131, p = 0.54), but hNMB receptor results correlated with rat NMB receptor (r = 0.71, p < 0.0001). These results elucidate the human and rat GRP-receptor pharmacophore for agonists differs markedly, whereas they do not for NMB receptors, therefore potential GRP-receptor agonists for human studies (such as Bn receptor-imaging/cytotoxicity) must be assessed on human Bn receptors. The current study provides affinities/potencies on a large number of potential agonists that might be useful for human studies. © 2011 Elsevier Inc. Source

Tsai C.,Peptide Research Laboratories | Leslie J.S.,Peptide Research Laboratories | Franko-Tobin L.G.,Peptide Research Laboratories | Prasnal M.C.,Peptide Research Laboratories | And 7 more authors.
Archives of Gynecology and Obstetrics | Year: 2013

Purpose: We investigated the effects of the anti-epilepsy drug valproic acid (VPA) alone and in combination in treating cervical cancer. Methods: VPA was investigated for its effects on cervical cancer Hela cell proliferation and tumor growth via in vitro and in vivo assays. Results: VPA induce cell growth suppression and cell cycle arrest, with an increase of Notch1 that acts as a tumor suppressor and the change of other tumor-associated genes such as p21, p63 and PCNA. VPA was also found to induce cell morphological change, with an increase of certain cell transformation markers such as snail1, snail2 and N-cadherin. Moreover, VPA could significantly up-regulate somatostatin receptor type II (SSTR2). Our in vivo study further demonstrated that VPA via inducing SSTR2 up-regulation extremely enhanced the anti-tumor ability of the SSTR2-preferential cytotoxic COL-SST conjugate in xenografts. Conclusions: VPA could not only suppress tumor progression but also provide a novel promising therapeutic choice in combination with a receptor-targeted cytotoxic conjugate via activating the specific receptor. © 2013 Springer-Verlag Berlin Heidelberg. Source

Moreno P.,U.S. National Institute of Diabetes and Digestive and Kidney Diseases | Mantey S.A.,U.S. National Institute of Diabetes and Digestive and Kidney Diseases | Nuche-Berenguer B.,U.S. National Institute of Diabetes and Digestive and Kidney Diseases | Reitman M.L.,U.S. National Institute of Diabetes and Digestive and Kidney Diseases | And 4 more authors.
Journal of Pharmacology and Experimental Therapeutics | Year: 2013

Bombesin-receptor-subtype-3 (BRS-3) is an orphan G-proteincoupled receptor of the bombesin (Bn) family whose natural ligand is unknown and which does not bind any natural Bnpeptide with high affinity. It is present in the central nervous system, peripheral tissues, and tumors; however, its role in normal physiology/pathophysiology is largely unknown because of the lack of selective ligands. Recently, MK-5046 [(2S)-1,1,1-trifluoro-2-[4-(1H-pyrazol-1-yl)phenyl]- 3-(4-{[1-(trifluoromethyl) cyclopropyl]methyl}-1H-imidazol-2-yl)propan-2-ol] and Bantag-1 [Boc-Phe-His-4-amino-5-cyclohexyl-2,4,5-trideoxypentonyl-Leu-(3- dimethylamino) benzylamide N-methylammonium trifluoroacetate], a nonpeptide agonist and a peptide antagonist, respectively, for BRS-3 have been described, but there have been limited studies on their pharmacology. We studied MK-5046 and Bantag-1 interactions with human Bn-receptors-human bombesin receptor subtype-3 (hBRS-3), gastrin-releasing peptide receptor (GRP-R), and neuromedin B receptor (NMB-R)-and compared them with the nonselective, peptide-agonist [D-Tyr6,βAla11,Phe13, Nle14]Bn-(6-14) (peptide #1). Receptor activation was detected by activation of phospholipase C (PLC), mitogen-activated protein kinase (MAPK), focal adhesion kinase (FAK), paxillin, and Akt. In hBRS-3 cells, the relative affinities were Bantag-1 (1.3 nM) > peptide #1 (2 nM) > MK-5046 (37-160 nM) > GRP, NMB (>10 μM), and the binding-dose- inhibition curves were broad (>4 logs), with Hill coefficients differing significantly from unity. Curve-fitting demonstrated high-affinity (MK-5046, Ki = 0.08 nM) and low-affinity (MK-5046, Ki = 11-29 nM) binding sites. For PLC activation in hBRS-3 cells, the relative potencies were MK-5046 (0.02 nM) > peptide #1 (6 nM) > GRP, NMB, Bantag-1 (>10 μM), and MK-5046 had a biphasic dose response, whereas peptide #1 was monophasic. Bantag-1 was a specific hBRS-3-antagonist. In hBRS-3 cells, MK-5046 was a full agonist for activation of MAPK, FAK, Akt, and paxillin; however, it was a partial agonist for phospholipase A2 (PLA2) activation. The kinetics of activation/duration of action for PLC/MAPK activation of MK-5046 and peptide #1 differed, with peptide #1 causing more rapid stimulation; however, MK-5046 had more prolonged activity. Our study finds that MK-5046 and Bantag-1 have high affinity/selectivity for hBRS-3. The nonpeptide MK-5046 and peptide #1 agonists differ markedly in their receptor coupling, ability to activate different signaling cascades, and kinetics/duration of action. These results show that their hBRS-3 receptor activation is not always concordant and could lead to markedly different cellular responses. Copyright © 2013 by The American Society for Pharmacology and Experimental Therapeutics. Source

Uehara H.,U.S. National Institutes of Health | Hocart S.J.,Peptide Research Laboratories | Gonzalez N.,U.S. National Institutes of Health | Mantey S.A.,U.S. National Institutes of Health | And 4 more authors.
Biochemical Pharmacology | Year: 2012

There is increased interest in the Bn-receptor family because they are frequently over/ectopically expressed by tumors and thus useful as targets for imaging or receptor-targeted-cytotoxicity. The synthetic Bn-analog, [d-Tyr 6, β-Ala 11, Phe 13, Nle 14]Bn(6- 14) [Univ.Lig] has the unique property of having high affinity for all three human BNRs (GRPR, NMBR, BRS-3), and thus could be especially useful for this approach. However, the molecular basis of this property is unclear and is the subject of this study. To accomplish this, site-directed mutagenesis was used after identifying potentially important amino acids using sequence homology analysis of all BnRs with high affinity for Univ.Lig compared to the Cholecystokinin-receptor (CCK AR), which has low affinity. Using various criteria 74 amino acids were identified and 101 mutations made in GRPR by changing each to those of CCK AR or to alanine. 22 GRPR mutations showed a significant decrease in affinity for Univ.Lig (>2-fold) with 2 in EC2[D97N, G112V], 1 in UTM6[Y284A], 2 in EC4[R287N, H300S] showing >10-fold decrease in Univ.Lig affinity. Additional mutations were made to explore the molecular basis for these changes. Our results show that high affinity for Univ.Lig by human Bn-receptors requires positively charged amino acids in extracellular (EC)-domain 4 and to a lesser extent EC2 and EC3 suggesting charge-charge interactions may be particularly important for determining the general high affinity of this ligand. Furthermore, transmembrane amino acids particularly in UTM6 are important contributing both charge-charge interactions as well as interaction with a tyrosine residue in close proximity suggesting possible receptor-peptide cation-π or H-bonding interactions are also important for determining its high affinity. © 2012 Elsevier Inc. All rights reserved. Source

Sun L.,Fudan University | Sun L.,Peptide Research Laboratories | Sun G.,Fudan University | Yu Y.,Fudan University | Coy D.H.,Peptide Research Laboratories
Anti-Cancer Agents in Medicinal Chemistry | Year: 2015

Hepatocellular carcinoma (HCC) is one of the most malignant cancers, with the second highest cancer death rate world-wide, next to lung cancer. The signaling mechanisms in HCC are currently not clear. Notch signaling, which is highly conserved and plays a critical role in many cancers, was found to be aberrantly upregulated in HCC tissues compared to normal liver tissues. Accumulating evidence supports that Notch signaling plays a significantly important role in HCC carcinogenesis. This review discusses the functions of Notch signaling in HCC and its potential therapeutic applications against this cancer. © 2015 Bentham Science Publishers. Source

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