title: Loss of p53 in stromal fibroblasts enhances tumor cell proliferation through nitric-oxide-mediated cyclooxygenase 2 activation.
abstract: Overexpression of cyclooxygenase 2 (COX-2) by stromal fibroblasts plays a critical role in the early stage of carcinogenesis. COX-2 expression is thought to be positively or negatively regulated by inflammatory chemical mediators or tumor suppressors. In this study, the contributions of inducible nitric oxide synthase (iNOS) and p53 to COX-2 expression were examined using mouse embryonic fibroblasts (MEFs) from wild-type, p53-deficient, iNOS-deficient, and p53/iNOS-deficient mice. These MEFs were treated with 1 μg/mL of lipopolysaccharide and 100 IU/mL of interferon gamma for up to 72 h. iNOS and COX-2 expression were analyzed by Western blotting. iNOS was induced earlier (16 h) in p53-deficient MEFs than in wild-type MEFs (48 h). Elevated expression of COX-2 was sustained for a longer duration in the p53-deficient MEFs. In contrast, COX-2 expression was reduced earlier in the iNOS-deficient MEFs. Addition of an exogenous NO donor (0.8 mM of S-nitroso-l-glutathione) to the iNOS-deficient MEFs augmented COX-2 expression. Co-culture with stimulated p53-deficient MEFs promoted cell proliferation of mouse rectal polyploid carcinoma CMT93 cells, but treatment with a COX-2-specific inhibitor counteracted this effect. These results suggest that loss of function of the p53 gene in stromal fibroblasts enhances COX-2 expression by enhancing iNOS expression and the resultant production of NO, contributing to the promotion of tumor growth.
authors.affiliation: Division of Applied Life Sciences, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University , Shimogamo , Japan.
authors.forename: S
authors.initials: S
authors.lastname: Wada
authors.forename: Y
authors.initials: Y
authors.lastname: Matsushita
authors.forename: H
authors.initials: H
authors.lastname: Tazawa
authors.forename: W
authors.initials: W
authors.lastname: Aoi
authors.forename: Y
authors.initials: Y
authors.lastname: Naito
authors.forename: A
authors.initials: A
authors.lastname: Higashi
authors.forename: H
authors.initials: H
authors.lastname: Ohshima
authors.forename: T
authors.initials: T
authors.lastname: Yoshikawa
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000235:genetics; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism*; D017353:Gene Deletion; D051379:Mice; D018345:Mice, Knockout; D009374:Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics; D015398:Signal Transduction; D017154:Stromal Cells / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*
chemical_list: D016159:Tumor Suppressor Protein p53; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D051546:Cyclooxygenase 2
keywords: carcinogenesis; colorectal caner; deficiency; prostaglandin E2; stromal cells