To determine whether the tumors develop on a normal or disturbed epigenetic background and how radiation affects this, we quantified genome-wide histone H3 methylation profiles in macroscopic normal intestinal tissue of young radiated and untreated MMR-deficient VCMsh2LoxP/LoxP (Msh2−/−) mice months before tumor onset. This evidence concerns the gene MRC1 and neoplasm.