KHC-4 inhibits ß-catenin expression in prostate cancer cells.

KHC-4 is a 2-phenyl-4-quinolone analogue that exhibits anticancer activity. Aberrant activation of ß-catenin signaling contributes to prostate cancer development and progression. Therefore, targeting ß-catenin expression could be a useful approach to treating prostate cancer. We found that KHC-4 can inhibit ß-catenin expression and its signaling pathway in DU145 prostate cancer cells. Treatment with KHC-4 decreased total ß-catenin expression and concomitantly decreased ß-catenin levels in both the cytoplasm and nucleus of cells. KHC-4 treatment also inhibited ß-catenin expression and that of its target proteins, PI3K, AKT, GSK3ß and TBX3. We monitored the stability of ß-catenin with the proteasomal inhibitor, MG132, in DU145 cells and found that MG132 reversed KHC-4-induced proteasomal ß-catenin degradation. We verified CDK1/ß-catenin expression in KHC-4 treated DU145 cells. We found that roscovitine treatment reversed cell proliferation by arresting the cell cycle at the G2/M phase and ß-catenin expression caused by KHC-4 treatment. We suggest that KHC-4 inhibits ß-catenin signaling in DU145 prostate cancer cells.

Pathways of assimilation of [13N]N2 and 13NH4+ by cyanobacteria with and without heterocysts.

The principal initial product of metabolism of [13N]N2 and 13NH4+ by five diverse cyanobacteria is glutamine. Methionine sulfoximine inhibits formation of [13N]glutamine except in the case of Gloeothece sp., an organism with a thick sheath through which the inhibitor may not penetrate. Thus, glutamine synthetase appears to catalyze the initial step in the assimilation of N2-derived or exogenous NH4+ by these organisms. [13N]Glutamate is, in all cases, the second major product of assimilation of 13N-labeled N2 and NH4+. In all of the N2-fixing cyanobacteria studied, the fraction of 13N in glutamine declines and that in glutamate increases with increasing times of assimilation of [13N]N2 and 13NH4+, and (Gloeothece again excepted) methionine sulfoximine reduces incorporation of 13N into glutamate as well as into glutamine. Glutamate synthase therefore appears to catalyze the formation of glutamate in a wide range of N2-fixing cyanobacteria. However, the major fraction of [13N]glutamate formed by Anacystis nidulans incubated with 13NH4+ may be formed by glutamic acid dehydrogenase. The formation of [13N]alanine from 13NH4+ appears to be catalyzed principally either by alanine dehydrogenase (as in Cylindrospermum licheniforme) or by a transaminase (as in Anabaena variabilis).

The pathways of assimilation of 13NH4+ by the cyanobacterium, Anabaena cylindrica.

The principal initial product of metabolism of 13N-labeled ammonium by Anabaena cylindrica grown with either NH4+ or N2 as nitrogen source is amide-labeled glutamine. The specific activity of glutamine synthetase is approximately half as great in NH4+-grown as in N2-grown filaments. After 1.5 min of exposure to 13NH4+, the ratio of 13N in glutamate to 13N in glutamine reaches a value of approximately 0.1 for N2- and 0.15 for NH4+-grown filaments, whereas after the same period of exposure to [13N]N2, that ratio has reached a value close to unity and is rising rapidly. During pulse-chase experiments, 13N is transferred from the amide group to glutamine into glutamate, and then apparently into the alpha-amino group of glutamine. Methionine sulfoximine, an inhibitor of glutamine synthetase, inhibits the formation of glutamine. In the presence of the inhibitor, direct formation of glutamate takes place, but accounts for only a few per cent of the normal rate of formation of that amino acid; and alanine is formed about as rapidly as glutamate. Azaserine reduces formation of [13N]glutamate approximately 100-fold, with relatively little effect on the formation of [13N]glutamine. Aminooxyacetate, an inhibitor of transaminase reactions blocks transfer of 13N to aspartate, citrulline, and arginine. We conclude, on the basis of these results and others in the literature, that the glutamine synthetase/glutamate synthase pathway mediates most of the initial metabolism of ammonium in A. cylindrica, and that glutamic acid dehydrogenase and alanine dehydrogenase have only a very minor role.