Expression of neighbor of Punc E11 in hepatocarcinogenesis induced by diethylnitrosamine

To identify preneoplastic markers for hepatocarcino-genesis, the expression levels of neighbor of Punc E11 (Nope), E-cadherin and α-fetoprotein (AFP) were investigated in carcinogen-treated embryonic cell lineages. Mouse embryonic stem cells (ESCs), hepatic progenitor cells (HPCs), and hepatocyte‑like cells (HCs) representing 0, 22, and 40 days of liver differentiation, respectively, were treated in vitro with diethylnitrosamine (DEN) at 4 doses (0, 1, 5, and 15 mM) for 24 h. The expression of Nope, E-cadherin and AFP was examined by quantitative real-time PCR, western blotting and immunocytochemistry. DEN treatment significantly increased the mRNA expression of Nope in ESCs and HPCs, and that of E-cadherin and AFP in all three cell lines, although the changes in expression were triggered by varying DEN concentrations. Immunofluorescence staining revealed that Nope was expressed at the cell membrane in ESCs and HPCs and within granules or in the cytoplasm of HCs, which was also stained by E-cadherin. DEN treatment induced Nope expression in ESCs, HPCs and HCs and caused a concomitant increase in E-cadherin expression. Although Nope expression clearly increased following tumor induction, its expression pattern changed with the developmental stage. In conclusion, we determined that Nope expression may carry prognostic significance during early hepatocarcinogenesis. Moreover, Nope expression may serve as a novel oncofetal surface marker for preneoplastic stages that are not identifiable by the commonly used marker, AFP.