Autophagy mediates resistance to gemcitabine treatment through a novel E2F1-p300-VMP1 pathway

VACCARO, M. I.; ALEJANDRO JAVIER ROPOLO; MOLEJÓN, M. I.; CATRINACIO, C.; RENNA, F.; BOGGIO, V.; GONZALEZ, C. D.

Southampton

Congreso; IAP/EPC Meeting 2014; 2014

International Association of Pancreatology & European Pancreatic Club

Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive human malignancies. Gemcitabine, a deoxycytidine analog, has become the standard chemotherapy for the treatment of advanced pancreatic cancer despite its poor efficacy because the relatively refractory of human pancreatic tumor cells. Autophagy is an evolutionarily conserved degradation process of cytoplasmic cellular constituents. It has been suggested that autophagy plays a role in both tumor suppression and tumor progression. Aims: Here we characterize a new molecular pathway, mediated by VMP1, an autophagy-related protein inducible by activated K-Ras. Materials & Methods: Highly resitant pancreatic cancer cells PANC-1, carrying activated K-Ras and BxPC-3 cells, that do not carry K-Ras mutation were used. We evaluated regulation of VMP1 promoter by Luciferase and Chromatin immunoprecipitation assays. Gemcitabine treatment effects on autophagy, cell survival and cell death were determinated. Results: Gemcitabine requires VMP1 expression to induce autophagy in highly resistant PANC-1 cells, but not in BxPC-3 cells. We indetified the transcription factor E2F1 as an effector of gemcitabine -induced autophagy. E2F1 binds to the VMP1 promoter in PANC-1 cells regulating the expression and promoter activity of VMP1. We also identified the histone acetyl-transferase p300 as a modulator of this promoter activity. Our data show that the E2F1-p300 activator/co-activator complex is part of the regulatory pathway controlling the expression and promoter activity of VMP1 triggered by gemcitabine in PANC1 cells. Finally, downregulation of VMP1 expression and pharmacological modulation of autophagy sensitize PANC-1 cells to apoptosis and diminish clonogenicity under gemcitabine treatment. Conclusion: Together, these data provide evidence of a transcriptional regulation mechanism of autophagy that integrates this cellular process into the complex network of events involved in PDAC chemoresistance.