the impact of dna demethylation on the upregulation of the nrn1 and tnfaip3 genes associated with advanced gastric cancer

Gastric cancer (gc) is the third leading cause of cancer-related death worldwide. very few therapeutic options are currently available in this neoplasia. the use of 5-aza-2′-deoxycytidine (5-azadc) was approved for the treatment of myelodysplastic syndromes, and this drug can treat solid tumours at low doses. epigenetic manipulation of gc cell lines is a useful tool to better understand gene expression regulatory mechanisms for clinical applications. therefore, we compared the gene expression profile of 5-azadc-treated and untreated gc cell lines by a microarray assay. among the genes identified in this analysis, we selected nrn1 and tnfaip3 to be evaluated for gene expression by rt-qpcr and dna methylation by bisulfite dna next-generation sequencing in 43 and 52 pairs of gc and adjacent non-neoplastic tissue samples, respectively. we identified 83 candidate genes modulated by dna methylation in gc cell lines. increased expression of nrn1 and tnfaip3 was associated with advanced tumours (p < 0.05). we showed that increased nrn1 and tnfaip3 expression seems to be regulated by dna demethylation in gc samples: inverse correlations between the mrna and dna methylation levels in the promoter of nrn1 (p < 0.05) and the intron of tnfaip3 (p < 0.05) were detected. reduced nrn1 promoter methylation was associated with iii/iv tnm stage tumours (p = 0.03) and the presence of helicobacter pylori infection (p = 0.02). the identification of demethylated activated genes in gc be useful in clinical practice, stratifying patients who are less likely to benefit from 5-azadc-based therapies.