E2F1, the Transcription Factor Related to Proliferation and Cell Death, Mediates Activation of Vmp1 Gene Promoter Inducing Autophagy in Pancreatic Tumor Cells

ROPOLO A; VACCARO MI

Miami

Congreso; American Pancreatic Association Meeting; 2013

American Pancreatic Association

E2F1, the Transcription Factor Related to Proliferation and CellDeath, Mediates Activation of Vmp1 Gene Promoter InducingAutophagy in Pancreatic Tumor CellsA. Ropolo, M. Giovenco, A. Lo Re, M.I. Molejon, C. Catrinacio, V. Boggio,M.I. Vaccaro. Institute for Biochemistry and Molecular Medicine,CONICET, University of Buenos Aires, Argentina.Autophagy is an evolutionarily preserved degradation process of cytoplasmiccellular constituents, which participates in cell response to disease. Wecharacterized VMP1 (Vacuole Membrane Protein 1) as an essential autophagyrelated-protein that mediates autophagy in pancreatic diseases. Gemcitabinetreatment induced early expression of VMP1 and autophagy in pancreaticcancer cells. However, the regulatory pathways that control vmp1 geneexpression and autophagy in pancreatic tumor cells are not fully understood.The retinoblastoma pathway is often inactivated in human tumors resulting inderegulated E2F activity that can induce both proliferation and cell death. E2F1expression has been correlated with higher tumor grade and worse patientsurvival in PDAC. The activation of E2F1 was reported to up-regulate theexpression of three autophagy genes (LC3, ATG1 and ATG5) and a damageregulatedautophagy modulator (DRAM). The aim of this work is to evaluatethe effect of E2F1 on VMP1 expression in pancreatic tumor cells. We foundthat overexpression of E2F1 transcription factor in Panc-1 and MiaPaCa-2pancreatic tumor cells induces VMP1 expression. We also demonstrated thatE2F1 expression induces autophagy analyzed by the increasing number ofRFP-LC3 positive cells with a punctate staining. Moreover, we showed thatp300, a classical co-activator transcription factor, cooperates with E2F1 inVMP1 promoter regulation. Conversely, RNAi knockdown of p300 impairsE2F1 induced activation of this promoter. Chromatin immunoprecipitationassays demonstrated that E2F1 binds to VMP1 promoter when cells weresubmitted to gemcitabine treatment. Together these data provide evidence thatE2F1 is a new regulatory factor modulating autophagy in pancreatic tumorcells. The knowledge of the mechanism of response to Gemcitabine treatmentby tumor cells will improve disease therapeutics