Altered expression of Skp2, c-Myc and p27 proteins but not mRNA after H. pylori eradication in chronic gastritis.

Helicobacter pylori infection is associated with increased gastric epithelial cell turnover and non-cardia gastric cancer. Cell cycle progression is dependent on the proteasomal degradation of p27, a cyclin-dependent kinase inhibitor and gastric tumor suppressor, following ubiquitination mediated by Skp2. c-Myc is a transcriptional repressor of p27 and also a target of Skp2. In vitro, H. pylori decreases p27 protein post-translationally. We aimed to determine how p27 is regulated by H. pylori in vivo. The effect of eradicating H. pylori on gastric epithelial p27, Skp2, and c-Myc proteins and mRNA was investigated in 22 patients with chronic gastritis, by immunohistochemistry and laser capture microdissection. The percentage of gastric antral epithelial cells expressing p27 protein was significantly higher after eradication of H. pylori (mean+/-s.e.m. 37+/-2.4% pre-eradication vs 55+/-2.8% post-eradication; P<0.001), while Skp2 and c-Myc protein-expressing cells were lower (Skp2: 35+/-3.8 vs 23+/-2.6%, P=0.009; c-Myc: 47+/-3.6 vs 30+/-3.8%, P<0.001). mRNA expressions of p27, Skp2, and c-Myc (normalized for 18SrRNA) were not changed by H. pylori eradication. H. pylori increases c-Myc and decreases gastric epithelial p27 protein expression in association with increased expression of Skp2, the regulator of p27's ubiquitin ligase complex. H. pylori may influence cell cycle progression and carcinogenesis through post-translational effects on specific gene expression.

Expression of uncoupling protein-2 in human colon cancer.

PURPOSE: Cancer cell survival depends on adaptive mechanisms that include modulation of oxidative stress. One such mechanism may be via up-regulation of uncoupling protein-2 (UCP2), a mitochondrial inner membrane anion carrier recently found to provide cytoprotection in nontumor cells by acting as a sensor and negative regulator of reactive oxygen species production. We hypothesized that UCP2 expression may be increased in colon cancer as part of tumor adaptation. EXPERIMENTAL DESIGN: UCP2 expression was characterized by real-time polymerase chain reaction and Western blotting using paired human colon adenocarcinoma and peritumoral specimens. Oxidant production was characterized by tissue malondialdehyde levels. Tissue microarrays constructed of 107 colon adenocarcinomas as well as representative specimens of hyperplastic polyps and tubular adenomas were used for UCP2 immunohistochemistry. RESULTS: UCP2 mRNA and protein levels were 3- to 4-fold higher in adenocarcinomas, and UCP2 mRNA levels showed significant correlation with increased tumor tissue malondialdehyde contents. Immunohistochemistry on tissue microarrays showed positive staining for UCP2 in most adenocarcinomas (86.0%); positive staining for UCP2 was seen less often in tubular adenomas (58.8%) and rarely seen in hyperplastic polyps (11.1%). CONCLUSIONS: UCP2 expression is increased in most human colon cancers, and the level of expression appears to correlate with the degree of neoplastic changes. These findings may foster the idea that UCP2 is part of a novel adaptive response by which oxidative stress is modulated in colon cancer.

Effects of sodium butyrate and acidic fibroblast growth factor on TDC32300 cultured cells.

BACKGROUND: Many studies have demonstrated that transition duct cells (TDC) are facultative liver stem cells. Our laboratory established TDC32300 cell lines with hepatic progenitor markers. The authors proposed that cell culture using sodium butyrate (NaBut) and acidic fibroblast growth factors (aFGF) may support the differentiation of TDC32300 cells along the hepatic lineage. METHODS: TDC32300 cells were cultured in four different conditions 1) STON media alone; 2) STON with NaBut in 3 different concentrations, 1 mM, 3.75 mM and 5 mM; 3) STON with aFGF; and 4) STON with aFGF and dexamethasone. After day 5, the cultured cells were fixed and stained with monoclonal antibodies to rat liver antigens and anti-proliferating nuclear antigen (PCNA). RESULTS: Proliferation of TDC32300 cells cultured in the high concentration of NaBut (3.75 and 5 mM) was inhibited. This phenomenon was confirmed by the reduction in cell number and decrease in PCNA expression. Irrespective of the concentration, NaBut did not alter the phenotype of the TDC32300 cultured cells. aFGF with or without dexamethasone also did not alter the phenotypic characteristic of TDC32300 cells. CONCLUSION: TDC32300 cells may not be the hepatic progenitors or that their differentiation may require other culture conditions.