In carcinogenesis epigenetic aberrations occur early, are widespread across the genome and are potentially reversible. DNA methylation (5mC) at gene promoters and CpG islands (CGIs) is well recognized for affecting gene expression. In contrast, little is known on the role of DNA methylation in distal regulatory elements (DREs). Based on recent genome-wide studies, we hypothesize that DREs are more sensitive than CGIs to changes in DNA methylation, thus they may function as primary responders to epigenetic therapies. We previously showed DREs are indeed epigenetically dynamic and prone to demethylation, the process that may involve a newly identified DNA modification, cytosine hydroxymethylation (5hmC). The molecular mechanisms by which these modifications are targeted to specific genomic locations are not well understood.The project aims to identify the role DNA methylation and hydroxymethylation play in the maintenance and functioning of DREs during cancer progression and treatment. For that, genome-wide methods will be developed for the identification of DREs followed by targeted enrichment using DNA capture array and sequencing. This will allow for simultaneous analysis of 5mC and 5hmC modifications at base-pair resolution. We will examine the effects of virus infection and chronic inflammation on DNA methylation and hydroxymethylation in cultured oral keratinoctes while focusing on the changes in transcription factor binding as a potential targeting mechanism. The effect of DNA methylation inhibitors will be examined to identify key methylation events within DREs required for cancer cell survival. Clinical relevance of the key methylated regions will then be evaluated on a panel of head and neck cancers from well characterized cohorts of patients.This investigation will reveal important molecular aspects of chromatin function in tumorigenesis, thereby improving prospects for developing personalized cancer therapies that target epigenetic modifications.