Helicobacter pylori is a major cause of the transdifferentiation into intestinal metaplasia that may develop gastric cancer. However, the molecular pathogenesis of this transdifferentiation is poorly understood. A SRY-related HMG box protein Sox2 is an essential transcription factor of organ development in brain, lung, and stomach. Our aim of this study was to investigate the mechanism responsible for regulation of Sox2 in host Th1-dominant response to H. pylori. Sox2 protein was immunohistochemically expressed in both human oxyntic and pyloric glands with H. pylori infection, but not in intestinal metaplasia. Western immunoblotting of gastric epithelial cell lines showed that IL-4, a Th2-related cytokine, dose dependently enhanced Sox2 expression among H. pylori infection-mediated cytokines. Small changes of Sox2 expression were observed after each treatment with IFN-gamma, IL-1beta, or TNF-alpha. IL-4-mediated Sox2 induction was suppressed by the inhibition of STAT6 activation with STAT6 RNA interference, and electrophoretic mobility shift assay indicated that activation of the Sox2 promoter by IL-4 occurred through the action of STAT6. Furthermore, H. pylori and IFN-gamma inhibited the phosphorylation of STAT6, resulting in the suppression of IL-4-mediated Sox2 expression. Immunohistochemical analyses showed significantly the suppressed STAT6 activity in H. pylori-infected human gastric mucosa. Additionally, downregulation of Sox2 by knockdown experiments led to intestinal phenotype with expressions of Cdx2 and MUC2. These results suggest that H. pylori and IFN-gamma interfere with the differentiation into oxyntic and pyloric glands by the downregulation of Sox2 on IL-4/STAT6 signaling, which may contribute to the transdifferentiation into intestinal metaplasia.
"Two additional lines of evidence further support that downregulation of SOX2 may be involved in early stages of gastric carcinogenesis. Downregulation of SOX2 could be detected in precursor lesions of gastric cancer such as intestinal metaplasia  and Helicobacter pylori infection, a strong risk factor of gastric cancer, could induce intestinal metaplasia through inhibition of SOX2 expression . It is possible that SOX2 also participate in the early carcinogenesis of endometrial cancer via interaction with other risk factors. "
[Show abstract][Hide abstract] ABSTRACT: This paper aimed at investigating the expression and methylation profiles of SOX2, a gene coding for the stem cell-related transcription factor SOX2, in endometrial carcinomas. By methylation-specific polymerase chain reaction (MS-PCR), the methylation status of SOX2 promoter region in 72 endometrial carcinomas and 12 normal endometrial samples was examined. Methylated allele was found in 37.5% (27/72) of endometrial carcinomas but only in 8.3% (1/12) of normal endometrial, significantly more frequent in cancers (P = .0472). SOX2 mRNA level was significantly reduced in endometrial carcinoma compared with nonneoplastic endometrium (P = .045). A significant correlation between SOX2 mRNA expression and hypermethylation of SOX2 was found (P = .024). Hypermethylation of SOX2 tended to be more frequently found in type II serous or clear cell adenocarcinoma. SOX2 methylation was also significantly correlated with shorter survival of patients (P = .046). In conclusion, epigenetic mechanisms may play a crucial role on the transcriptional regulation of SOX2 and loss of SOX2 expression may be related to endometrial carcinogenesis.
Obstetrics and Gynecology International 08/2010; 2010. DOI:10.1155/2010/682504
[Show abstract][Hide abstract] ABSTRACT: Background
The signal transducer and activator of transcription 6 (Stat6), a member of the family of DNA-binding proteins, has been identified as a critical cell differentiation modulator in breast cancer cells. As of yet, the mechanisms underlying this function have remained largely unknown. To further elucidate the role of Stat6 in breast cancer development, we investigated the consequences of exogenous Stat6 expression.
Proliferation assays and flow cytometry assays were conducted to evaluate the putative role of Stat6 on cell proliferation. To this end, we produced synchronized cells after a double thymidine block, as confirmed by FACS analysis. mRNA levels of Stat6 were measured by RNase protection analysis. To confirm the interaction among proteins, we employed GST pull-down assays and immunoprecipitation assays. Luciferase assays and ChIP assays were used to assess the transcriptional activity.
Compared to control breast cancer cells, we found that exogenous Stat6 expression plays a critical role in controlling cell proliferation. Also in different breast tumor cell lines, endogenous Stat6 expression was found to be positively related to a lower proliferation rate. Interestingly, in human breast cancer cells Stat6 functions in G1/S cell cycle progression, and the growth-inhibitory effect of Stat6 was shown to be mediated by induction of the G1 cyclin-dependent kinase inhibitors p21Cip1/WAF1 (p21) and p27Kip1 (p27). Simultaneously, G1-related cyclin/cyclin-dependent kinase activities and pRB phosphorylation were markedly reduced, and cell cycle progression was blocked in the G1 phase. Stat6 knockdown resulted in enhanced cell proliferation and a decrease in p21 and p27 mRNA levels in the steroid-responsive and non-responsive T-47D and MDA-MB-231 cell lines, respectively. In addition, the stimulatory effect of Stat6 on p21 and p27 gene transcription was found to be associated with interaction of Stat6 with the transcription factor Sp1 at the proximal Sp1-binding sites in their respective promoters.
Together, these results identify Stat6 as an important cell differentiation regulatory protein functioning, at least in part, by interacting with Sp1 to activate the p21 and p27 gene promoters in breast cancer cells.
[Show abstract][Hide abstract] ABSTRACT: The intestinal environment is considered to play an important role both in colorectal tumor development and in the evolution and modulation of mucosal immunity. Studies in animals reared in germ-free (GF, without any intestinal microflora) versus conventional (CV, with regular microflora in bowel) conditions can aid in clarifying the influence of bacteria on carcinogenesis and anti-cancer immune responses in situ. The lower incidence of colon cancers and better immunological parameters in GF animals versus CV ones after chemically-induced carcinogenesis raises questions about specific characteristics of the immunological networks in each respective condition. Different levels of tolerance/regulatory mechanisms in the GF versus CV animals may influence the development of immune responses not only at the level of mucosal, but also at the systemic, immunity. We hypothesize that GF animals can better recognize and respond to evolving neoplasias in the bowel as a consequence of their less-tolerogenic immunity (i.e., due to their more limited exposure to antigens to become tolerated against at the intestinal level). In this paper, we review the role of bacteria in modulating gut environment and mucosal immunity, their importance in cancer development, and aspects of immune regulation (both at local and systemic level) that can be modified by bacterial microflora. Lastly, the use of GF animals in comparison with conventionally-raised animals is proposed as a suitable and potent model for understanding the inflammatory network and its effect on cancer immunity especially during colorectal cancer development.
Journal of Immunotoxicology 12/2009; 6(4):217-26. DOI:10.3109/15476910903334343 · 2.05 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.