Genome-wide mapping of ASCL2 and CTNNB1 in hepatoblastoma cell lines

Hepatoblastoma (HB) is the most common pediatric liver malignancy; however, hereditary predisposition and acquired molecular aberrations related to HB clinicopathological diversity are not well understood. We performed an integrative genomic profiling of 163 pediatric liver tumors (154 HB and 9 hepatocellular carcinoma) based on data acquired from a cohort study (JPLT-2). The total number of somatic mutations was found to be extremely low (0.52 /Mb on exonic regions) but correlated with age at diagnosis. TERT promoter mutations are prevalent in the tween HBs, selective in the transitional liver cell tumor (TLCT, > 8 years old). DNA methylation profiling revealed that classical HBs are characterized by the specific hypomethylated enhancers, which are enriched with binding sites for ASCL2, a regulatory transcription factor for definitive endoderm in Wnt-pathway. Prolonged upregulation of ASCL2, as well as fetal-liver-like methylation patterns of IGF2 promoters, suggests their “cell of origin” derived from the premature hepatoblast, similar to intestinal epithelial cells, which are highly proliferative. Systematic molecular profiling of HB is a promising approach to understanding the epigenetic drivers of hepatoblast carcinogenesis and clues for risk stratification. Genome-wide mapping of ASCL2 and CTNNB1 in hepatoblastoma cell lines