5-Fluorouracil suppresses nitric oxide biosynthesis in colon carcinoma cells.
Nitric oxide is an important cellular mediator that plays a role in regulating cellular proliferation of both normal and tumor cells. In the present study, we characterized nitric oxide production by the human colon adenocarcinoma cell line DLD-1 and examined the effects of 5-fluorouracil (5-FUra), an antimetabolite effective against colon tumors, on nitric oxide production. IFN-gamma was found to be a potent inducer of nitric oxide production in DLD-1 cells. This effect was dependent on L-arginine and blocked by the nitric oxide synthase inhibitors NG-monomethyl-L-arginine, nitroarginine, and aminoguanidine. Production of nitric oxide by DLD-1 cells was due to the expression of the inducible (type II) form of nitric oxide synthase. mRNA for the nitric oxide synthase was present in both untreated and IFN-gamma-stimulated cells, as determined by RT-PCR, suggesting that expression of enzyme is regulated posttranscriptionally. Treatment of DLD-1 cells with concentrations of 5-FUra that are not growth inhibitory or cytotoxic strongly inhibited their ability to express nitric oxide synthase and produce nitric oxide in response to IFN-gamma. This effect was not reversed with thymidine, indicating that inhibition of nitric oxide production was due to incorporation of 5-FUra into RNA. However, pretreatment of DLD-1 cells with 5-FUra before stimulation with IFN-gamma also suppressed nitric oxide production. Thus, inhibition of nitric oxide production was not due directly to incorporation of 5-FUra into the mRNA for nitric oxide synthase. Taken together, these data suggest that inhibition of nitric oxide biosynthesis in colon tumor cells by 5-FUra may underlie, at least in part, the efficacy of this antitumor agent.
Jin
Y
Y
Department of Environmental and Community Medicine, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway 08854, USA.
Heck
D E
DE
DeGeorge
G
G
Tian
Y
Y
Laskin
J D
JD
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D003110:Colonic Neoplasms / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005472:Fluorouracil / Q000494:pharmacology*; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D017471:Receptors, Interferon / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000964:Antimetabolites, Antineoplastic; D004791:Enzyme Inhibitors; D017471:Receptors, Interferon; D009569:Nitric Oxide; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D005472:Fluorouracil