An immunohistochemical analysis of antioxidant and glutathione S-transferase enzyme levels in normal and neoplastic human lung.

Samples of normal human lung and six major types of human lung carcinomas were immunostained for antioxidant enzymes (manganese and copper, zinc superoxide dismutases, catalase, and glutathione peroxidase) and six isoenzymes of glutathione S-transferase staining was generally low in tumor cells compared with the high level of staining noted in respiratory epithelium. A notable exception was heterogeneity in immunostaining for manganese superoxide dismutase in lung adenocarcinoma, which showed both positive and negative cells in the same tumor. Tumor stromal cells (fibroblast-appearing cells) often showed strong immunostaining for manganese superoxide dismutase, while stromal cells were negative for other antioxidant and glutathione S-transferase enzymes. None of the carcinomas studied had significant levels of catalase or glutathione peroxidase; this finding has potential clinical relevance since it indicates that these tumors cannot detoxify hydrogen peroxide. The low levels of antioxidant and glutathione S-transferase enzymes in tumor cells is consistent with the hypothesis that these enzymes are markers of cell differentiation.