Relationship Between Expression Of Tet Proteins And CagA-induced Gastric Cancer

Tet Family Protein has been well-known as a dioxygenasemodifying DNA by hydroxylating5mC to5hmC, and the mechanism,signal pathway are deeply illustrated. Recently studies suggested thatTet1proteins play an important role in ESCs differentiation andepigenetic regulation; Tet2proteins are tightly associated with myeloidmalignancies, and TET2gene has been generally accepted as a tumorrepressor; Tet3–mediated DNA hydroxylation is involved in epigeneticreprogramming of the zygotic paternal. In addition, as a virus factor ofH.pylori, CagA proteins enhance the inflammation in host cells resultingin more oxidative stress, which greatly induced the gastric carcinogenicity.We try to investigate the association between the aberrant expression ofthe Tet proteins and CagA of Helicobacter pylori（H.p） in the multipleprocess of gastric carcinogenesis， and to explore the possiblecarcinogenic mechanisms of CagA factor.Quantitative RT-PCR was used to detect mRNA expression inGES-1and GC cells. Immuncytochemistry and Western blotting wereperformed to detect the TET proteins in GES-1and GC cells. The resultsconfirmed that three Tet protein members were different distribution inGES-1cells and GC cells. Tet1and Tet2expression levels varied greatly.GES-1cells were transfected with pEGFP-CagA; a cell oxidative stress model was constructed with200uM H₂O₂. Immuncytochemistry andWestern blotting were applied to detect the Tet2proteins expression intreated-cells. Generation of intracellular ROS and cell cycle wereexamined by flow cytometer. The results displayed that the relativeexpression levels of Tet in GES-1cells were significantly lower than thatin GC cells, CagA-transfected GES-1cells and oxidative stress cells,which was consent with the results of Tet immunostaining.In this study, we concluded that CagA factor can induce ROSproduction and cell cycle disruption, and offers the possibility of DNAdamage, replication error and mutation; in return lead to the highexpression of TET2, which disturbs the balance of demethylation andmethylation, finally resulting in the formation of gastric cancer.