Immunohistochemical localization of cytochrome P450 2E1 in human pulmonary carcinoma and normal bronchial tissue.

Cytochrome P450 2E1 (CYP2E1) is a major xenobiotic-metabolizing enzyme but data concerning its extrahepatic expression are few. CYP2E1 can metabolically activate many procarcinogens and therefore its presence in the lung might play a role in bioactivation of procarcinogens, so we studied the expression and localization of CYP2E1 in primary pulmonary carcinomas and surrounding normal bronchial tissue from 28 patients. Seromucous glands showed expression of CYP2E1 in 19 and bronchial epithelium in 18 of the 28 samples of normal bronchial tissue. Thirteen of the corresponding cases of primary pulmonary carcinoma showed staining for CYP2E1. In 11 of these 13 cases, CYP2E1 was also present in normal bronchial tissue. There was no statistically significant difference in the expression of CYP2E1 between adenocarcinomas and squamous cell carcinomas. No association was observed between the expression of CYP2E1 in tumour tissue and normal bronchial tissue. However, there was a significant correlation between the expression of CYP2E1 in seromucous glands and bronchial epithelium (r = 0.61, P < 0.01) of normal tissue. We conclude that CYP2E1 can be present in both normal and neoplastic bronchial tissue.