Hypermethylation associated with inactivation of the SOCS-1 gene, a JAK/STAT inhibitor, in human hepatoblastomas.

We recently demonstrated inactivation in hepatocellular carcinomas (HCCs) of the gene encoding SOCS1/JAB1/SSI-1, a JAK-binding protein that regulates the JAK/STAT signal-transduction pathway. In a follow-up immunochemical investigation of expression of SOCS-1 in hepatoblastomas (HBLs), the protein was markedly reduced in half of the HBL tumors we examined. CpG-rich regions upstream of the SOCS-1 gene were hypermehylated in 7 of the 15 HBL cases. The results suggest that hypermethylation may play an important role in silencing the SOCS-1 gene, not only in adult HCCs, but also in liver tumors arising in childhood.