AIM: To investigate the role of cytochrome P450 (CYP) in the carcinogenesis of squamous-cell carcinoma (SCC) in human esophagus by determining expression patterns and protein levels of representative CYPs in esophageal tissue of patients with SCC and controls. METHODS: mRNA expression of CYP2E1, CYP2C, CYP3A4, and CYP3A5 was determined using RT-PCR in both normal and malignant esophageal tissues of patients with untreated esophageal SCC (n = 21) and in controls (n = 10). Protein levels of CYP2E1, CYP2C8, CYP3A4, and CYP3A5 were measured by Western blot. RESULTS: Within the group of SCC patients, mRNA expression of CYP 3A4 and CYP2C was significantly lower in malignant tissue (-39% and -74%, respectively, P < 0.05) than in normal tissue. Similar results were found in CYP3A4 protein levels. Between groups, CYP3A4, CYP3A5, and CYP2C8 protein concentration was significantly higher in non-malignant tissue of SCC patients (4.8-, 2.9-, and 1.9-fold elevation, P < 0.05) than in controls. In contrast, CYP2E1 protein levels were significantly higher in controls than in SCC patients (+46%, P < 0.05). CONCLUSION: Significant differences exist in protein levels of certain CYPs in non-malignant esophageal tissue (e.g. CYP2C8, CYP3A4, CYP3A5, and CYP2E1) between SCC patients and healthy subjects and may contribute to the development of SCC in the esophagus. AIM: To investigate the role of cytochrome P450 (CYP) in the carcinogenesis of squamous-cell carcinoma (SCC) in human esophagus by determining expression patterns and protein levels of representative CYPs in esophageal tissue of patients with SCC and controls. METHODS: mRNA expression The CYP2E1, CYP2C, CYP3A4, and CYP3A5 were determined using RT-PCR in both normal and malignant esophageal tissues of patients with untreated esophageal SCC (n = 21) and in controls , and CYP3A5 were measured by Western blot. RESULTS: Within the group of SCC patients, mRNA expression of CYP 3A4 and CYP2C was significantly lower in malignant tissue (-39% and -74%, respectively, P <0.05) than in normal tissue . Similar groups were found in CYP3A4 protein levels. Between groups, CYP3A4, CYP3A5, and CYP2C8 protein concentrations were significantly higher in non-malignant tissue of SCC patients (4.8-, 2.9-, and 1.9-fold elevation, P <0.05) in controls. In co CONCLUSION: Significant differences exist in protein levels of certain CYPs in non-malignant esophageal tissues (eg CYP2C8, CYP3A4, CYP3A5, and CYP2E1) between SCC patients and healthy subjects and may contribute to the development of SCC in the esophagus.