PBX1 attributes as a determinant of connexin 32 downregulation in -related gastric carcinogenesis.

AIM

To clarify the mechanisms of connexin 32 (Cx32) downregulation by potential transcriptional factors (TFs) in ()-associated gastric carcinogenesis.

METHODS

Approximately 25 specimens at each developmental stage of gastric carcinogenesis [non-atrophic gastritis, chronic atrophic gastritis, intestinal metaplasia, dysplasia and gastric carcinoma (GC)] with infection [ (+)] and 25 normal gastric mucosa (NGM) without infection [ (-)] were collected. After transcriptional factor array analysis, the Cx32 and PBX1 expression levels of -infected tissues from the developmental stages of GC and NGM with no infection were measured by real-time polymerase chain reaction (RT-PCR) and Western blot analysis. Regarding -infected animal models, the Cx32 and PBX1 mRNA expression levels and correlation between the gastric mucosa from 10 Mongolian gerbils with long-term colonization and 10 controls were analyzed. PBX1 and Cx32 mRNA and protein levels were further studied under the -infected condition as well as PBX1 overexpression and knockdown conditions .

RESULTS

Incremental PBX1 was first detected by TF microarray in -related gastric carcinogenesis. The identical trend of PBX1 and Cx32 expression was confirmed in the developmental stages of -related clinical specimens. The negative correlation of PBX1 and Cx32 was confirmed in -infected Mongolian gerbils. Furthermore, decreased PBX1 expression was detected in the normal gastric epithelial cell line GES-1 with 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.

CONCLUSION

PBX1 is one of the determinants in the Cx32 promoter targeting site, preventing further damage of gap junction protein in -associated gastric carcinogenesis.