Characterization of the transcriptional signature of C/EBPbeta isoforms (LAP/LIP) in Hep3B cells: Implication of LIP in pro-survival functions

• Published in: Journal of hepatology 2011-06, Vol.54 (6), p.1185-1194
• Main Authors: Saint-Auret, Gaëlle, Danan, Jean-Louis, Hiron, Martine, Blache, Céline, Sulpice, Eric, Tendil, Simon, Daveau, Maryvonne, Gidrol, Xavier, Salier, Jean-Philippe
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; C/EBPbeta isoforms; Carcinoma, Hepatocellular - genetics; Carcinoma, Hepatocellular - pathology; CCAAT-Enhancer-Binding Protein-beta - genetics; CCAAT-Enhancer-Binding Protein-beta - physiology; Cell Death - drug effects; Cell Death - genetics; Cell Death - physiology; Cell Line, Tumor; Cell Proliferation - drug effects; Cell Survival - drug effects; Cell Survival - genetics; Cell Survival - physiology; ChIP-on-chip; Gastroenterology and Hepatology; Gastroenterology. Liver. Pancreas. Abdomen; Gene Expression Profiling; Genetic Engineering; Hepatoma cell death; Humans; Life Sciences; Liver Neoplasms - genetics; Liver Neoplasms - pathology; Liver. Biliary tract. Portal circulation. Exocrine pancreas; Medical sciences; Models, Biological; Oligonucleotide Array Sequence Analysis; Paclitaxel - pharmacology; Protein Isoforms - genetics; Protein Isoforms - physiology; Staurosporine - pharmacology; Target genes; Transcription, Genetic; Transcriptome; Tumors
• ISSN: 0168-8278; 1600-0641
• DOI: 10.1016/j.jhep.2010.09.021

Background & Aims C/EBPbeta is an important mediator of several cellular processes, such as differentiation, proliferation, and survival of hepatic cells. However, a complete catalog of the targets of C/EBPbeta or the mechanism by which this transcription factor regulates certain liver-dependent pathways has not been clearly determined. Two major natural isoforms of this transcription factor exist: the liver-enriched activating protein (LAP) and the liver-enriched inhibitory protein (LIP), a functional LAP antagonist. In this study, we used the opposing transcriptional effects driven by LAP and LIP to determine the genuine C/EBPbeta molecular signature in the Hep3B human hepatoma cell line. We subsequently investigated the role of each of the LAP and LIP isoforms in drug-induced Hep3B cell death. Methods We engineered Hep3B cells with regulated LAP or LIP expression using the Tet-off expression system. The genes that showed inverse regulation by LAP and LIP were identified by cDNA array analysis. The cohort of direct-C/EBPbeta-targets was distinguished from indirect-targets by ChIP-on-chip analysis. Results We characterized 676 genes by this approach. Among these genes, 39 are novel direct targets of C/EBPbeta. Eleven of these new direct targets are involved in cell survival, suggesting critical roles for LAP/LIP isoforms in this cellular process. Therefore, we examined the effects of LAP and LIP over-expression on cell survival. We show that LIP promotes survival in staurosporine- or taxol-induced Hep3B cell death. Conclusions Our study provides new molecular and cellular insights into the role of C/EBPbeta in cells of hepatic origin.