Genome-wide DNA methylation profiling of gastrointestinal neuroendocrine tumors to identify hypermethylation of mTOR, Wnt, and Notch pathways in GI NET pathogenesis.

212 Background: Aberrant DNA methylation is known to play an important role in the pathogenesis of many human cancers, however little is known about its role in gastrointestinal neuroendocrine tumours (GI NET) development. We report the first unbiased genome-wide DNA methylation analysis of a large cohort of GI NETs, aiming to identify key methylation variable positions (MVPs) specific to GI NETs which may contribute to tumorigenesis and metastatic progression. Methods: Illumina Infinium Human Methylation 450 Array analysis was performed on 56 cases of GI NET DNA extracted from macrodissected tumour (n=67) and normal (n=29) specimens. Tumours were gastrointestinal primaries (n=39) or metastases (liver, mesenteric, omental or lymph node, n=28) of low (n=35), intermediate (n=17) or high grade (n=3)(unknown grade n=12). Data analysis was performed using the "ChAMP" custom pipeline and pathway analyses were performed using "GREAT," "WebGestalt," and "GSEA" web tools. A Bonferroni adjusted significance thresho...