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

ALEJANDRO JAVIER ROPOLO; VACCARO, M. I.; CATRINACIO, C.

Buenos Aires

Congreso; III International Congress in Translational Medicine; 2016

International Master/PhD Program in Biomedical Sciences (IMBS). Facultad de Farmacia y Bioquímica y Facultad de Medicina, Universidad de Buenos Aires.

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. Here we characterize a new molecular pathway, mediated by VMP1, an autophagy-related protein inducible by activated K-Ras, by which gemcitabine is able to trigger autophagy in human pancreatic tumor cells. We demonstrated that gemcitabine requires VMP1 expression to induce autophagy in highly resistant pancreatic cancer cells PANC-1 carrying activated K-Ras, but not in BxPC-3 cells that do not carry K-Ras mutation. Analysis of the mechanisms identified E2F1, a transcription factor that is regulated by the retinoblastoma pathway, as an effector of gemcitabine-induced autophagy. E2F1 regulates the expression and promoter activity of VMP1. Chromatin immunoprecipitation assays demonstrated that E2F1 binds to the VMP1 promoter in PANC-1 cells. We also identified the histone acetyltransferase 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 PANC 1 cells. Finally, downregulation of VMP1 expression and pharmacological modulation of autophagy sensitize PANC-1 cells to apoptosis and diminish clonogenicity under gemcitabine treatment. 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.