Nonpeptide neuromedin B receptor antagonists inhibit the proliferation of C6 cells

The ability of nonpeptide antagonists to interact with neuromedin B recepto rs on C6 cells was investigated. 2-[3-(2,6-Diisopropylphenyl)-ureido]3-(1H- indol-3-yl)-2-methyl-N-(1-pyridin-2-yl-cyclohexylmethyl)-proprionate (PD165 929), 3-(1H-indol-3-yl)-2-methyl-2-[3(4-nitro-phenyl)-ureido]-N-(1-pyridin- 2-yl-cyclohexylmethyl)-propionamide (PD168368) and 3-(1H-indol-3-yl)-N-[1-( 5-methoxy-pyridin-2-yl)-cyclohexylmethyl]-2-methyl-2-[3-(4-mitro-phenyl)-ur eido]-propionamide (PD176252) inhibited (I-125-Tyr(0))neuromedin B binding with IC50 values of 2000, 40 and 50 nM, respectively. Because neuromedin B is a G-protein coupled serpentine receptor, the effects of neuromedin B ant agonists on second messenger production and proliferation were investigated . PD168368 inhibited the ability of 10 nM neuromedin B to cause elevation o f cytosolic Ca2+, whereas it had no effect on basal cytosolic Ca2+. PD16836 8 inhibited the ability of 100 nM neuromedin B to cause elevation of c-fos mRNA. Also, PD168368 in a dose-dependent manner inhibited the ability of 10 0 nM neuromedin B to cause phosphorylation of focal adhesion kinase. Using a [3-(4,5 dimethylthiazol-2-yl)-2.5-diphenyl-2H-tetrazolium bromide] assay, the order of antagonist potency to inhibit C6 proliferation was PD168368 = PD176252 > PD165929. Also, 1 muM PD168368 and PD176252 significantly inhib ited colony number using a proliferation assay in vitro. PD168368 significa ntly inhibited C6 xenograft growth in nude mice in vivo. These results indi cate that PD168368 is a C6 cell neuromedin B receptor antagonist, which inh ibits proliferation. (C) 2000 Elsevier Science B.V. All rights reserved.