utation at nucleotide position 652 in a breast carcinoma. Chen et al. reported that cancerassociated Aa mutations AEB 071 contribute to cancer development by inducing functional haploinsufficiency, disturbing PP2A holoenzyme composition and altering the enzymatic activity of PP2A. The loss of PPP2R1A protein expression has also been observed in breast cancer. However, the specific functional genetic variants located in the PPP2R1A promoter and its association with the risk of HCC has not yet been defined. In our previous study, we designated a proximal region of 685 bp as the core promoter of PPP2R1A because it displayed the highest transcriptional activity in luciferase assays. In the current study, we constructed proximal promoter fragments mirroring the PPP2R1A allelotypes, including either the 2241 or the 2241 G allele, to determine transcriptional activity. Promoter activity assays revealed that the allelotype 2241 exhibited a higher promoter activity. Our results suggest that different allelotypes composed of the 2241 variant influence the transcriptional regulation of the PPP2R1A promoter. A recent report demonstrated that the 2241 variant was located in the PPP2R1A promoter region, which is regulated by the binding of TFs such as ETS-1, CREB, AP-2a and Sp1. In our previous study, we also reported that the functional 2241 variant may influence its binding affinity to the transcription factor NF-kB. Moreover, it was confirmed that the activity of the PPP2R1A promoter was affected by 2241 variants via NF-kB activation in our current study. The DNA methylation of promoter regions is one of the major regulatory mechanisms controlling gene transcription and expres- sion in various biological processes. 12584108 The term DNA methylation usually refers to the post-synthetic methylation of deoxycytosine residues at the 59 position to form deoxymethylcytosine. Frequently, both the core promoter and transcription initiation site are included within CpG islands, and gene expression is completely repressed when these islands become hypermethylated. DNA methylation is essential for mammalian development and health, and aberrant DNA methylation contributes to the pathogenesis and progression of disease, including cancer. A few studies have investigated the effect of methylation on the expression of the PP2A subunit genes. It has been reported that hypomethylation of the PP2A-B55b gene promoter induces its expression, which was found to be involved in the expression of estrogen receptors in human breast cancer cell 
lines. Another study demonstrated that the methylation of deoxycytosine in the CpG islands 18284029 limited the binding of the phosphorylated cAMP response element-binding protein and decreased the activity of the PP2A-Ca promoter. In contrast, the binding of Sp1 to a GC box within the promoter region was not influenced by DNA methylation. However, for the PPP2R1A gene promoter, no evidence was found for the association between DNA methylation and the regulation of gene transcription. We first predicted the presence of concentrated CpG islands in the PPP2R1A gene promoter and then speculated that epigenetic mechanisms may be involved in the transcriptional regulation of PPP2R1A. The influence of promoter methylation on PPP2R1A transcriptional activity was demonstrated using constructs with both unmethylated and methylated forms. Our data indicate that the hypermethylation of the PPP2R1A promoter significantly reduced the transcriptional regulatory activity.
