A novel E2F1-p300-VMP1 pathway mediates gemcitabine-induced autophagy in pancreatic cancer cells carrying oncogenic KRAS

CATRINACIO, C.; ORQUERA, T.; ALEJANDRO JAVIER ROPOLO; RENNA, F.; BOGGIO, V.; VACCARO, M. I.

Congreso; Digestive Disease Week 2020; 2020

American Gastroenterological Association

Autophagy is an evolutionarily preserved degradation process of cytoplasmic cellular constituents, which participates in cell response to disease. We previously characterized VMP1 (Vacuole Membrane Protein 1) as an essential autophagy related-protein that mediates autophagy in pancreatic diseases. We also demonstrated that VMP1-mediated autophagy is induced by HIF-1a in colon-cancer stem cell lines, conferring resistance to photodynamic treatment. Here we identify a new molecular pathway by which gemcitabine is able to trigger autophagy in human pancreatic tumor cell lines that are considered pancreatic cancer stem cells. We demonstrated that gemcitabine requires VMP1 expression to induce autophagy in the highly resistant PANC-1 and MIAPaCa-2 cells that carry activated KRAS. E2F1 is a transcription factor that is regulated by the retinoblastoma pathway. We found that E2F1 is an effector of gemcitabine-induced autophagy and regulates the expression and promoter activity of VMP1. Chromatin immunoprecipitation assays demonstrated that E2F1 binds to the VMP1 promoter in PANC-1 and MIAPaCa-2 cells. We have also identified the histone acetyltransferase p300 as a modulator of VMP1-promoter activity. Our data showed 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 pancreatic cancer stem cells. Moreover, downregulation of E2F1 and VMP1 sensitized PANC-1 and MIAPaCa-2 cells to gemcitabine treatment. Finally, we found that neither VMP1 nor E2F1 are induced by gemcitabine treatment in BxPC-3 cells, which do not carry oncogenic KRAS and are sensitive to chemotherapy. In conclusion, we have identified the E2F1-p300-VMP1 pathway as a novel transcriptional regulation mechanism of autophagy in pancreatic cancer stem cells. These results strongly support that VMP1-mediated autophagy may integrate the complex network of events involved in pancreatic ductal adenocarcinoma chemo-resistance. Our experimental findings point at E2F1 and VMP1 as novel potential therapeutic targets in precise treatment strategies for pancreatic cancer.