The Prognostic Significance of Whole Blood Global and Specific DNA Methylation Levels in Gastric Adenocarcinoma

Abstract

BackgroundEpigenetics, particularly DNA methylation, has recently been elucidated as important in gastric cancer (GC) initiation and progression. We investigated the clinical and prognostic importance of whole blood global and site-specific DNA methylation in GC.MethodsGenomic DNA was extracted from the peripheral blood of 105 Omani GC patients at diagnosis. DNA methylation was quantified by pyrosequencing of global DNA and specific gene promoter regions at 5 CpG sites for CDH1, 7 CpG sites for p16, 4 CpG sites for p53, and 3 CpG sites for RUNX3. DNA methylation levels in patients were categorized into low, medium, and high tertiles. Associations between methylation level category and clinicopathological features were evaluated using χ2 tests. Survival analyses were carried out using the Kaplan-Meier method and log rank test. A backward conditional Cox proportional hazards regression model was used to identify independent predictors of survival.ResultsOlder GC patients had increased methylation levels at specific CpG sites within the CDH1, p53, and RUNX-3 promoters. Male gender was significantly associated with reduced global and increased site-specific DNA methylation levels in CDH1, p16, and p53 promoters. Global DNA low methylation level was associated with better survival on univariate analysis. Patients with high and medium methylation vs. low methylation levels across p16 promoter CpG sites, site 2 in particular, had better survival. Multivariate analysis showed that global DNA hypermethylation was a significant independent predictor of worse survival (hazard ratio (HR) = 2.0, 95% CI: 1.1–3.8; p = 0.02) and high methylation mean values across p16 promoter sites 1–7 were associated with better survival with HR of 0.3 (95% CI, 0.1–0.8; p = 0.02) respectively.ConclusionsAnalysis of global and site-specific DNA methylation in peripheral blood by pyrosequencing provides quantitative DNA methylation values that may serve as important prognostic indicators.

The study of hypermethylation in blood leukocytes of irradiated parents and their children

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Dietary factors, epigenetic modifications and obesity outcomes: Progresses and perspectives

“…In this sense, although it is of great interest to study the baseline epigenetic differences in obesity-related tissues, such as adipose or liver, peripheral blood mononuclear cells (or otherwise white cells) are being preferably used because of their less-invasive nature, low risk, and high diagnostic accuracy (Widschwendter et al, 2008). However, the study of specific DNA methylation in serum or whole blood should be encouraged as its economic cost is low, its availability is very easy and its prognostic significance has been demonstrated in different types of cancer, such as lung (Fujiwara et al, 2005) or gastric adenocarcinoma (Al-Moundhri et al, 2010). The biological significance of whole-genome methylation appears irrelevant and usually lacks of prognostic value in metabolic diseases because a low sensibility.…”