Exploring genome-wide DNA methylation profiles altered in hepatocellular carcinoma using Infinium HumanMethylation 450 BeadChips

We examine genome-wide DNA methylation profiles in 66 pairs of HCC tumor and adjacent non-tumor tissues. After Bonferroni adjustment, a total of 130,512 CpG sites significantly differed in methylation level in tumor compared to non-tumor tissues, with 28,017 CpG sites hypermethylated and 102,495 hypomethylated in tumor tissues. Most (60.1%) significantly hypermethylated CpG sites are located in CpG islands. These results demonstrate the significance of aberrant DNA methylation in HCC tumorigenesis. Bisulfite modification of 1µg DNA was conducted using an EZ DNA Methylation Kit (Zymo Research, Irvine, CA) according to the manufacturer’s procedure. The Infinium Methylation 450K assay was performed according to Illumina’s standard protocol. Six HCC tumor/adjacent non-tumor tissue pairs were processed on the same chip to avoid chip-to-chip variation.