Different individuals possess slightly different genetic information and show genetically-determined differences
in several enzyme activities due to genetic variability. Following an integrated approach,we studied the polymorphisms
andmethylation of sites contained in the 5′ flanking region of themetabolizing enzyme CYP2E1 in correlation
to its expression in both tumor and non-neoplastic liver cell lines, since to date little is known about the
influence of these (epi)genetic elements in basal conditions and under induction by the specific inductor and a
demethylating agent. In treated cells, reduced DNA methylation, assessed both at genomic and gene level, was
not consistently associatedwith the increase of enzyme expression. Interestingly, the Rsa/Pst haplotype differentially
influenced CYP2E1 enzyme expression. In addition, regarding the Variable Number of Tandem Repeats
polymorphism, cells with A4/A4 genotype showed a greater expression inhibition (ranging from 20% to 30%)
compared with others carrying the A2/A2 one, while those cells bringing A2/A3 genotype showed an increase
of expression (of 25%, about). Finally, we demonstrated for the first time that the A2 and A3 CYP2E1 alleles
play a more important role in the expression of the enzyme, compared with other (epi)genetic factors, since
they are binding sites for trans-acting proteins