Journal
GASTROENTEROLOGY
Volume 128, Issue 5, Pages 1354-1368Publisher
W B SAUNDERS CO-ELSEVIER INC
DOI: 10.1053/j.gastro.2005.01.055
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Background & Aims: Inflammatory mediators and cell fate genes, such as the Notch gene family, both have been implicated in cancer biology. Because cholangio-carcinomas arise in a background of inflammation and express the inflammatory mediator inducible nitric oxide synthase (NOS), we aimed to determine whether NOS expression alters Notch expression and signaling. Methods: Notch receptor and ligand expression in human liver was evaluated by immunohistochemistry. The effect of iNOS and NO on Notch-1 expression was examined in cell lines. Results: Notch-1, but not other Notch receptors, were up-regulated by cholangiocytes in primary sclerosing cholangitis and cholangiocarcinoma. The colocalization of Notch-1 and NOS also was observed in large bile ducts from the hilar region of primary sclerosing cholangitis patients. Notch-1 expression in murine cholangiocytes was NOS dependent. iNOS expression also facilitated Notch signaling by inducing the nuclear translocation of its intracellular domain and the expression of a transcriptional target, hairy and enhancer of split (Hes)-1. The gamma-secretase inhibitor N-[N-(3,5-Difluorophenacetyl-L-alanyl)-S-phenylglycine]-t-butyl ester, which blocks Notch signaling, enhanced tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis in cholangiocarcinoma cells. Conclusions: These data implicate a direct link between the inflammatory mediator NOS and Notch signaling, and have implications for the development and progression of cholangiocarcinoma.
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