Human Colorectal Cancer Stage-dependent Global DNA Hypomethylation of Cancer-associated Fibroblasts.

Background/Aim: Cancer-associated fibroblasts (CAFs) play an important role in tumor development and progression. The prevailing consensus favors the view that a specific epigenetic signature underpins the stable CAF phenotype. The aim of the present study was to assess global DNA methylation in CAFs during the adenoma-carcinoma sequence in non-familial sporadic human colorectal cancer (CRC). Patients and Methods: Immunohistochemical staining of nuclear 5-methylcytosine (5'-meCyt) was performed in matched samples of colonic tumor tissue and normal colonic mucosa excised from six patients with adenomas and four with adenocarcinomas. The staining intensity was expressed semi-quantitatively as the immunohistochemical staining score (ISS). Results: ISS values of human colonic CAFs and adenomatous samples were 14.00+/-2.2 and 14.08+/-1.8, respectively, showing no statistically significant difference. In contrast, a marked trend was found towards global DNA hypomethylation in CAFs from adenocarcinomatous specimens compared to matched normal mucosa: ISS: 9.25+/-2.44 (range=6-11) vs. 16.17+/-0.75, respectively, p< 0.03. Conclusion: Final stages of cancer development in CRC are associated with global DNA hypomethylation in stromal CAFs.