Identification of chromatin-accessible domains in non-alcoholic steatohepatitis-derived hepatocellular carcinoma.

Non-alcoholic steatohepatitis (NASH) is becoming one of the major causes of hepatocellular carcinoma (HCC) in the United States and Western countries; however, the molecular mechanisms associated with NASH-related liver carcinogenesis are not well understood. In the present study, we investigated cancer-associated chromatin alterations using a model that resembles the development of NASH-related HCC in humans. An assay for transposase-accessible chromatin with high throughput sequencing (ATAC-seq) identified 1677 tumor-specific chromatin-accessible regions in NASH-derived HCC tissue samples. Using a combined analysis of ATAC-seq and global gene expression data, we identified 199 differentially expressed genes, 139 up-regulated and 60 down-regulated. Interestingly, 15 of the 139 up-regulated genes had accessible chromatin sites within 5 Kb of the transcription start site (TSS), including Apoa4, Anxa2, Serpine1, Igfbp1, and Tubb2a, genes critically involved in the development of NASH and HCC. We demonstrate that the mechanism for the up-regulation of these genes is associated with the enrichment of chromatin-accessible regions by transcription factors, especially NFATC2, and histone H3K4me1 and H3K27ac gene transcription-activating marks. These data underline the important role of chromatin accessibility perturbations in reshaping of the chromatin landscape in NASH-related HCC.