IRS1 and hepatocellular carcinoma: On the other hand, in HCC, once accumulation of β-catenin occurs as a result of somatic mutations within the APC or β-catenin gene, not only genes involved in cell proliferation, such as c-Myc and cyclin D1, but also the Irs1 genes are upregulated, which activates insulin signaling including Akt phosphorylation, and further stimulates proliferation of HCC.