Octamer-binding transcription factor 4 expression in diethylnitrosamine-induced hepatocarcinogenesis of mice

Abstract

To clarify the role of stem cells in hepatocarcinogenesis, octamer-binding transcription factor 4 (Oct4) expression was investigated in mouse liver and embryonic cell lineages. In vivo, ten ICR mice were divided into two groups and treated with saline or diethylnitrosamine (DEN) at 14 days of age, and were sacrificed at 6 h after treatment. Livers were fixed in 10% neutral phosphate buffered formalin, embedded in paraffin, sectioned to a thickness of 5 μm, and immunohistochemical analysis of Oct4 was carried out. In vitro, mouse embryonic stem cells, hepatic progenitor cells and hepatocytes, representing 0, 22 and 40 days of differentiation, respectively, were treated with DEN at four doses (0, 1, 5 and 15 mM; G1, G2, G3 and G4, respectively) for 24 h and RNA was isolated and Oct4 and Gadd45a mRNA were investigated. In vivo, Oct4 expression was not detected in saline-treated livers. However, its expression was appeared in hepatocytes of mice treated with DEN, showing cytoplasmic staining. In vitro, Oct4 expression was significantly different for G4 at day 0 (P point. Gadd45a expression was significantly different in G4 (P<0.01) at day 0 and G4 at day 40 (P<0.01) compared with that of G1 at each time point. Taken together, Oct4 expression was increased by DEN treatment in hepatocytes, however, not in embroyonic stem cells and hepatic progenitor cells. This suggests that Oct4 expression may be modulated in the hepatocarcinogenesis induced by DEN.