Altered 5-Hydroxymethylcytosine Landscape in Primary Gastric Adenocarcinoma

Multiple factors, including genetic and epigenetic fluctuations, have been linked to gastric cancer formation and progression. Cytosine methylation (5mC) has been recognized as a critical epigenetic mark in the mammalian genome. The recent discovery of 5-hydroxymethylcytosine (5hmC), which is generated by ten-eleven translocation (TET) enzymes, provides new perspectives to understand DNA methylation-related plasticity. In this study, we show that gastric tumors display significant loss of 5hmC. Using matched distant normal, peripheral, and tumor primary tissues, we performed genome-wide profiling of 5hmC and identified differentially hydroxymethylated regions (DhMRs) specifically associated with gastric tumors. Gene ontology analyses indicated that DhMRs (both loss of 5hmC and gain of 5hmC) were enriched among the genes involved in specific pathways. Interestingly, the binding motif of hypoxia-inducible factor 1 (HIF1) is enriched among both peripheral and tumor DhMRs, while the Myc-binding motif is specifically enriched among only tumor DhMRs. Tumor progression analyses revealed a unique set of DhMRs that correlate with tumor progression. These data together suggest that alteration of 5hmC could potentially contribute to the tumorigenesis of gastric tumors.