Differential methylation of G-protein coupled receptor signaling genes in gastrointestinal neuroendocrine tumors
Abstract Neuroendocrine tumors (NETs) of the small intestine undergo large chromosomal and methylation changes. The objective of this study was to identify methylation differences in NETs and consider how the differentially methylated genes may impact patient survival. Whole genome methylation and chromosomal copy number varation (CNV) of NETs from the small intestine and appendix was measured Tumors were divided into three molecular subtypes according to CNV results: chromosome 18 loss (18LOH), MultiCNV, and NoCNV. Comparison of 18LOH tumors with MultiCNV and NoCNV tumors identified 901 differentially methylated genes which are over represented with sevenG-protein coupled receptor (GPCR) pathways and the gene encoding somatostatin (SST), a clinical target for NETs. Patient survival based on low versus high methylation in all samples identified four significant genes (p-<0.05) OR2S2, SMILR, RNU6-653P and AC010543.1. Within the 18LOH molecular subtype tumors, survival differences were identifiedin high versus low methylation of 24 genes. The most significant is TRHR (p < 0.01), a GPCR with multiple FDA-approved drugs. By separating NETs into different molecular subtypes based on chromosomal changes, we find that multiple GPCRs and their ligands appear to be regulated through methylation and correlated with survival. Opportunities for better treatment strategies based on molecular features exist for NETs.