Up-regulation of I-2PP2A/SET gene expression in rat primary hepatomas and regenerating livers

I-2PP2A/SET, an inhibitor of protein phosphatase 2A, is supposed to be one of the oncoproteins associated with human myeloid leukemia. The I-2PP2A/SET gene expression was observed ubiquitously among all the rat tissues examined, but low in liver. Of interest is that the expression in the rat primary hepatomas and hyperplastic nodules was significantly elevated. The experiments using regenerating livers after partial hepatectomy showed that the expression of I-2PP2A/SET mRNA was low at the quiescent hepatocytes, but up-regulated at 12–24 h after partial hepatectomy, which corresponds to the mid G1 to S transition in the cell cycle. These results suggested the importance of I-2PP2A/SET in the hepatocarcinogenesis and hepatic cell proliferation.