As the expression of β1 subunit was observed to be up-regulated in diethylnitrosamine-treated mouse livers and in human HCC (hepatocellular carcinoma) tissues [37] and the β1 subunit has caspase activity that could degrade the key cell-cycle regulator, p27Kip1 [29,38], we speculated that the expression of β1 is up-regulated in other tumour tissues or cells. Here, CDKN1B is linked to hepatocellular carcinoma.