PBX1 attributes as a determinant of connexin 32 downregulation inHelicobacter pylori-related gastric carcinogenesis

Abstract

AIMTo clarify the mechanisms of connexin 32 (Cx32) downregulation by potential transcriptional factors (TFs) in Helicobacter pylori (H. pylori)-associated gastric carcinogenesis.METHODSApproximately 25 specimens at each developmental stage of gastric carcinogenesis [non-atrophic gastritis, chronic atrophic gastritis, intestinal metaplasia, dysplasia and gastric carcinoma (GC)] with H. pylori infection [H. pylori (+)] and 25 normal gastric mucosa (NGM) without H. pylori infection [H. pylori (-)] were collected. After transcriptional factor array analysis, the Cx32 and PBX1 expression levels of H. pylori-infected tissues from the developmental stages of GC and NGM with no H. pylori infection were measured by real-time polymerase chain reaction (RT-PCR) and Western blot analysis. Regarding H. pylori-infected animal models, the Cx32 and PBX1 mRNA expression levels and correlation between the gastric mucosa from 10 Mongolian gerbils with long-term H. pylori colonization and 10 controls were analyzed. PBX1 and Cx32 mRNA and protein levels were further studied under the H. pylori-infected condition as well as PBX1 overexpression and knockdown conditions in vitro.RESULTSIncremental PBX1 was first detected by TF microarray in H. pylori-related gastric carcinogenesis. The identical trend of PBX1 and Cx32 expression was confirmed in the developmental stages of H. pylori-related clinical specimens. The negative correlation of PBX1 and Cx32 was confirmed in H. pylori-infected Mongolian gerbils. Furthermore, decreased PBX1 expression was detected in the normal gastric epithelial cell line GES-1 with H. pylori infection. Enforced overexpression or RNAi-mediated knockdown of PBX1 contributed to the diminished or restored Cx32 expression in GES-1 and the gastric carcinoma cell line BGC823, respectively. Finally, dual-luciferase reporter assay in HEK293T cells showed that Cx32 promoter activity decreased by 30% after PBX1 vector co-transfection, indicating PBX1 as a transcriptional downregulator of Cx32 by directly binding to its promoters.CONCLUSIONPBX1 is one of the determinants in the Cx32 promoter targeting site, preventing further damage of gap junction protein in H. pylori-associated gastric carcinogenesis.

Proteomic and transcriptomic studies of BGC823 cells stimulated with Helicobacter pylori isolates from gastric MALT lymphoma

“…Consistent with this, several studies on the gene expression profiles stimulated with H. pylori used human gastric cancer cell line but not human normal gastric epithelial cell line [26][27][28], and BGC823 cell line were frequently used to study the H. pylori related gastric carcinogenesis and related disease [29][30][31]. Since there were still no specific cell line to study the H. pylori related MALT lymphoma, in this study, we selected BGC823 cell line for further analysis to get as much information as possible.…”

Transition from normal to cancerous cell by precancerous niche (PCN) induced chronic cell-matrix stress

“…The association between pre-B-cell leukemia transcription factor homeobox (PBX) with PBX1-4 in human and H. pylori is of interest: H. pylori increases the transcriptional factor PBX1 followed by downregulation of connexin 32 (Cx32) [55]. Decreased Cx32 is correlated with "the degree of tumor cell differentiation with unrestricted growth control" ( [56] reviewed in [55]).…”

How doesHelicobacter pyloricause gastric cancer through connexins: An opinion review

“…A previous study reported that the expression levels of Cx32 and Cx43 mRNA decreased gradually during H. pylori -associated gastric carcinogenesis, and this result is associated with the hypermethylation of the promoters of these genes[76]. H. pylori infection may upregulate some transcription factors, such as GATA-3[77] and PBX-1[58]. These transcription factors can serve as the determinants in the Cx32 promoter targeting site and thereby inhibit Cx32 expression.…”

“…Gastric tissue mainly produces Cx26, Cx32, Cx37, Cx40, Cx43, and Cx45[49-57]. Previous studies have shown that, compared to tissues or cells of the normal gastric mucosa, the expression of Cxs dramatically decreases in GC[58-61]. Therefore, the variations in Cxs can serve as important biomarkers that imply the development of different cancers.…”