Furthermore, we used a DNA methylation inhibitor, 5-Aza-dC, in normal hepatocellular L02 cells to confirm the effect of promoter demethylation on gene expression. Our results indicate that the level of PPP2R1A mRNA was increased in cells after 5-Aza-dC treatment and that hypomethylation of the promoter was one of the AMI-1 mechanisms responsible for the regulation of PPP2R1A expression. Therefore, our results indicate that the methylation status of the PPP2R1A promoter might be one of the epigenetic mechanisms regulating key tumor suppressor genes involved in the transcriptional regulatory of the PP2A-Aa gene, which might suggest a novel gene target during hepatocarcinogenesis and could provide a novel route for the development of a new class of chemopreventers and anti-oncological agents. Although the aforementioned results indicate that methylation plays an important role in the regulation of PPP2R1A transcriptional activity, the effects of the 2241 genetic variant on the transcriptional regulation of PPP2R1A is not completely dependent on the DNA methylation status present in the promoter region of the gene. A few such instances reported previously in various cancers also support the results of our study and the conclusion that genetic variants/polymorphism and methylation in different target genes can play an independent role in the transcriptional regulatory mechanism. Here, 7531648 our findings contribute novel information regarding the gene transcription of PPP2R1A regulated by polymorphism and methylation in the promoter region through the genetic and epigenetic mechanisms in hepatocarcinogenesis. However, the molecular basis of these association remains to be further determined. Recently, a few studies have investigated the association between PPP2R1A variants and cancer risk. Dupont et al. performed a nested case-control study of Caucasian women to evaluate genetic variations in the intron region of PPP2R1A for their potential contribution to the risk of breast cancer. They Functional SNP in PPP2R1A Promoter and Risk of HCC identified significant risk and protective haplotypes in the PP2A structural subunit Aa isoform, with an odds ratios of 1.63 for the risk haplotype and 0.55 for the protective haplotype. Women with both the PPP2R1A risk haplotype and a history of proliferative breast disease had an OR of 2.44 for the subsequent development of breast cancer. The results of Dupont et al. are consistent with multiple independent 22582137 lines of study that have all suggested a key role for PPP2R1A in the development of cancer, including the viral- and toxin-induced transformation of cell culture systems and the somatic mutation of genes encoding the PP2A subunits in multiple tumor types. Moreover, other studies have demonstrated that some 
of PP2A subunits play important roles in HCC development or treatment. Duong et al. also reported that Hepatitis C virus-induced overexpression of PP2Ac contributes to hepatocarcinogenesis and inhibits DNA damage repair. However, few studies have investigated the association between PPP2R1A promoter polymorphism and HCC genetic susceptibility in diverse ethnic groups. In our case-control study, which was frequency-matched by age, sex, we genotyped the 2241 variant of the PPP2R1A promoter to investigate its association with the risk of HCC in a Han Chinese population. The genotype frequencies among controls strongly fit Hardy-Weinberg disequilibrium, suggesting that the selection of subjects was random in this popu
