Loss of glutathione S-transferase (GST) μ phenotype in colorectal adenocarcinomas from patients with a GSTM1 positive genotype

Glutathione S-transferase (GST) mu phenotype was assessed in colon tissue from patients with ulcerative colitis and colorectal neoplasms that were positive for GSTM1 genotype. GST mu protein (enzyme linked immunosorbent assay) was absent in 2/9 unaffected colon tissue (22.3%), 4/13 tissues with chronic ulcerative colitis (CUC) (30.7%), 4/11 adenomas (36.4%) and 7/14 adenocarcinomas (50.0%; P less than or equal to 0.05). GST-H-3-trans-stilbene oxide activity was detected in all tissues except 1/13 (7.6%) CUC tissues and 7/14 (50.0%, P less than or equal to 0.05) colorectal adenocarcinomas. Immunoreactive GST mu was observed in colonic epithelial cells but not in adjacent neoplastic cells by immunohistochemistry. Two-dimensional electrophoresis revealed several mu class isoforms in cytosol from unaffected colon that were absent in matched tumor cytosol. These results indicate that GSTM1 genotype may not necessarily reflect GST mu phenotype in colorectal tumors. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.