Decreased expression of cytochrome P450 2E1 is associated with poor prognosis of hepatocellular carcinoma

Cytochrome P450-2E1 (CYP2E1) is one of the major hepatic enzymes involved in the metabolism of procarcinogen. Our study aimed to investigate the differential expression level of CYP2E1 and its clinicopathological significance in hepatocellular carcinoma (HCC). CYP2E1 revealed low level of expression in 70% of the tumor tissues, when compared to the adjacent nontumor tissues, at both mRNA and protein levels. The low expression of CYP2E1 was significantly correlated with the aggressive tumor phenotype, including poor differentiation status (by the Edmondson grading system) (p=0.038), absence of tumor capsule (p=0.030) and younger age of the patients (p=0.002). Multivariate analysis indicated that CYP2E1 expression level and pTNM stage were independent prognostic factors for disease-free survival. CYP2E1 was also shown to have a differential expression level in different liver tissues. The level of CYP2E1 was significantly higher in nontumor tissues from HCC patients compared to the intermediate level in cirrhosis livers from noncancer patients and normal livers from healthy persons. Tumor tissues were shown to have the lowest expression level. In conclusion, our results have shown that CYP2E1 is upregulated in the nontumor tissue and downregulated in tumor tissue, which is associated with aggressive tumor type and poor prognosis of the patients. It suggested that the differential expression of CYP2E1 may play an important role in HCC tumorigenesis.