Characterization of murine hepatoma cells with regard to their dependence on cyclin E1

In C57BL/6 mice with a floxed cyclin E1 (CcnE1) gene (CcnE1f/f), hepatocellular carcinomas were induced using diethylnitrosamine (DEN). Hepatocyte-derived cells from pre-cancerous but tumor-free liver tissue (referred to as CcnE1f/fpreCL) and from large, solid HCC nodules (referred to as CcnE1f/fHCC) were isolated and immortalized in vitro. Deletion of CcnE1 in CcnE1f/fpreCL cells resulted in cell cycle arrest and death while CcnE1f/fHCC cells grew almost normal after loss of CcnE1. The underlying differences of both cell types regarding the transcriptome were analyzed in the present experiment. Four independent CcnE1f/fpreCL cell lines (R1-R4) and 3 independent HCC-derived cell lines (CcnE1f/fHCC, NR1-3) were infected with an adenovirus encoding cre-recombinase (adv-cre) in order to delete CcnE1. For the control experiment the same cell lines were infected with adenovirus expressing GFP (adv-GFP). Please note that 2 out of 4 preCL cell lines (CcnE1f/fpreCL clone 3 and clone 4) also contained a floxed Cdk2 allele. All preCL cell lines underwent cell cycle arrest after CcnE1 deletion, and all HCC cells grew normal in absence of CcnE1. Cells were harvested 3 days after infection and analyzed. Cells were compared to primary hepatocytes from CcnE1f/f mice (Ref-Hep1-3).