Evaluation of effect of inflammaton on mediators in the signaling pathway TNF-a, on DNA damage response and interaction with network miRNAs in gastric carcinogenesis

Abstract

Gastric adenocarcinoma is often associated with H. pylori infection, it induces an inflammatory and immune response in the host leading to the activation of pro- and anti-inflammatory mediators that produce reactive oxygen species (ROS) and nitrogen in the infected mucosa increasing oxidative stress, genotoxic and DNA damage. As a result, the occurrence of genetic instability, changes in the pattern of gene expression and miRNA are observed. Our group has contributed to studies focusing on the relationship between inflammation x cancer and recent results have highlighted the TNFA gene due to its increased expression both in samples from patients with chronic gastritis infected with H. pylori, and gastric cancer. Also there was a negative correlation between the expression of TNFa mRNA with miRNAs and the occurrence of interaction networks, suggesting the involvement of miRNAs in modulating cytokine expression in response to infection. Thus, TNF-±, a cytokine with tumor promoting function and apoptosis and its signaling pathway initiated by the binding with its TNFR1 and TNFR2 receptors play an important role in inflammation and cancer. On this issue we intend to evaluate the occurrence of changes in the expression of mediators and receptors of the extrinsic pathway of apoptosis mediated by TNF-± and miRNAs group that target genes of this pathway after induction with H. pylori extract in cell lines of gastric adenocarcinoma, as well as the participation of TNFR1 and TNFR2 receptors and mRNA-miRNA interaction networks that act in the regulation of these processes. These conditions will be evaluated parameters such as cell proliferation and apoptosis. Subsequently, to investigate the expression of genes and miRNAs in gastric cancer samples with and without infection by H. pylori. The results may highlight important changes in members of the TNF-± pathway signaling due to induction of inflammation and miRNAs that contribute to regulating mechanism, in addition to the role of TNFR1 and TNFR2 receptors. Changes in mediating this pathway may also reflect changes in cellular processes such as cell proliferation and apoptosis, when imbalanced, provide the cascade of progression of gastric cancer. Another important consequence of the inflammatory process is the increased production of ROS that cause injuries that damage DNA and which, if not repaired, can lead to the accumulation of mutations with the risk of malignant progression. The repair by base excision (BER) required for removing the damage induced by ROS and increased regulation of this pathway has been described as an adaptive response to survival of cancer cells in the tumor microenvironment. Therefore, studies are needed that target repair enzymes such as endonuclease APE1, a crucial component of BER, which has been observed with increased expression in various types of tumors. Also to be evaluated complex network of processes involved in response to DNA damage (DDR), which suffer the influence of miRNAs that are differentially activated after exposure to mutagenic compounds, thereby altering the sensitivity of cells to damaged DNA and cellular responses as cell cycle arrest, DNA repair and apoptosis. Thus we propose to evaluate the responses in gastric adenocarcinoma cell lines treated with hydrogen peroxide and / or H. pylori extract associated with gene silencing of APE1. It will evaluate the level of oxidative stress, the occurrence of double-strand breaks in DNA and the expression of miRNAs involved in DDR in response to treatments and APE1 gene silencing, as well as parameters such as cell proliferation and apoptosis. Expression of the gene and APE1 of miRNAs will also be assessed in samples of patients with gastric cancer. The results may provide relevant information on the importance of BER repair and APE1 gene as a promising therapeutic target. (AU)