English: Sequential sections of a segment of colon epithelium near a colorectal cancer showing reduced or absent expression of PMS2 (A), ERCC1 (B) and ERCC4 (C) in the colon crypts. This tissue segment is from a histologically normal area of a colon resection of a male patient who had an adenocarcinoma in the sigmoid colon. For PMS2 (A), there is absent expression in cell nuclei of the crypt body, the crypt neck and the colonic lumen surface for all epithelial cells. For ERCC1 (B), there is reduced expression in most of the cell nuclei of the crypts, but there is high expression in cell nuclei at the neck of the crypts and in the adjacent colonic lumen surface. For ERCC4 (XPF) (C), there is absent expression in most of the cell nuclei of the crypts and in the colonic lumen in this area of tissue, but detectable expression at the neck of some crypts. The reductions or absence of expression of these DNA repair genes in this tissue appears to be due to epigenetic repression.^[1] Original image, also in a publication.^[1]