Inhibitors of endogenous nitrogen oxide formation block the promotion of neoplastic transformation in C3H 10T1/2 fibroblasts.
The endogenous production of nitric oxide (NO) and its role in the neoplastic transformation of C3H 10T1/2 mouse fibroblasts were investigated. NO production, as indicated by NO2- in the culture medium, was increased in cells initiated with 3-methylcholanthrene or stimulated with the combination of interferon-gamma (IFN gamma, 10 ng/ml) plus bacterial lipopolysaccharide (LPS, 1 micrograms/ml). NO2- was detectable within 24-48 h of IFN gamma/LPS treatment and accumulated to micromolar concentrations within 4 days. NO production was inhibited in a dose-dependent manner by analogs of L-arginine in which the terminal guanidino nitrogen is blocked, consistent with NO production by the oxidative deamination of L-arginine by nitric oxide synthase (NOS). IFN gamma/LPS-stimulated cells expressed a 4.4 kb mRNA which hybridized to a probe for the mouse macrophage-inducible NOS. Expression of the rat cerebellar constitutive NOS was not detected in these cells. Arginine analogs added to the culture medium during the post-confluence promotional stages of the C3H 10T1/2 transformation assay blocked the formation of transformed foci in a dose-dependent manner comparable to their inhibition of NO production. These data demonstrate that C3H 10T1/2 mouse fibroblasts are a useful model for the study of the effects of endogenous NO production in carcinogenesis and suggest that NO plays a significant role in the promotional phase of neoplastic transformation of these cells.
Mordan
L J
LJ
Molecular Oncology Program, University of Hawaii, Manoa, Honolulu 96813.
Burnett
T S
TS
Zhang
L X
LX
Tom
J
J
Cooney
R V
RV
D000594:Amino Acid Oxidoreductases / Q000235:genetics; D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000187:drug effects* / Q000235:genetics; D002478:Cells, Cultured; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D015870:Gene Expression / Q000235:genetics; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D008809:Mice, Inbred C3H; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase; D009602:Nitrosamines / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics
D008070:Lipopolysaccharides; D009602:Nitrosamines; D012333:RNA, Messenger; D009569:Nitric Oxide; C002741:N-nitrosomorpholine; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases