Transcriptional activity of the tandem repeat polymorphism in the 5'-flanking region of the human CYP2E1 gene.

Background: There are remarkable interindividual differences in the expression of cytochrome P-4502E1(CYP2E1), which in turn may alter susceptibility to alcohol-related diseases and various cancers. We recently characterized the tandem repeat polymorphism in the 5'-flanking region of the human CYP2E1 gene and found that subjects with the homozygous mutant-type (A4/A4) may be at higher risk of developing esophageal cancer. In this study, we determined how this tandem repeat polymorphism alters transcriptional activities of the human CYP2E1 gene by transfection studies.

Methods: The 5'-flanking region (-2,562 base pair to +9 base pair) of the CYP2E1 gene from three individuals of different genotypes (A2/A2, A2/A4, A4/A4) was amplified by polymerase chain reaction. The polymerase chain reaction products placed in front of a luciferase reporter gene were transfected into human hepatoblastoma cells, human esophageal cancer cells, and human uterus cancer cells. Transcriptional activities were determined by the dual-luciferase assay. When indicated, ethanol (50 mM) was included in the culture medium. CYP2E1 messenger RNA levels in peripheral lymphocytes were measured by the real-time reverse transcription-polymerase chain reaction using the LightCycler system.

Results: The construct including the tandem repeat region exhibited luciferase activities in both A2 and A4 type. It was of note that the activity produced by the A4 allele was significantly greater than that by A2 allele in HeLa cells (p < 0.001). CYP2E1 messenger RNA levels in peripheral blood lymphocytes were comparable between the two genotypes.

Conclusion: Transcriptional activity of the mutant allele of the tandem repeat polymorphism in the 5'-flanking region of the CYP2E1 gene is greater than that of the wild type.