A Novel E2F1-EP300-VMP1 Pathway Mediates Gemcitabine-Induced Autophagy in Pancreatic Cancer Cells Carrying Oncogenic KRAS

Abstract

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 (hypoxia inducible factor 1 subunit alpha) in colon-cancer tumor cell lines, conferring resistance to photodynamic treatment. Here we identify a new molecular pathway, mediated by VMP1, by which gemcitabine is able to trigger autophagy in human pancreatic tumor cell lines. We demonstrated that gemcitabine requires the VMP1 expression to induce autophagy in the highly resistant pancreatic cancer cells PANC-1 and MIAPaCa-2 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 cells. We have also identified the histone acetyltransferase EP300 as a modulator of VMP1 promoter activity. Our data showed that the E2F1-EP300 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, 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-EP300-VMP1 pathway that mediates gemcitabine-induced autophagy in pancreatic cancer 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.

Mitochondrial Dynamics and VMP1-Related Selective Mitophagy in Experimental Acute Pancreatitis

“…This plasmid loses the green color at acidic pH, which makes a sophisticated marker of mitochondrial input to the autolysosome, that is, a good marker of mitophagy ( Kim et al, 2013 ). (e) GFP-sh-VMP1 plasmid for VMP1 down-regulation designed by Ropolo et al (2020) .…”

Targeting hypoxic tumor microenvironment in pancreatic cancer

“…Autophagy is an evolutionarily preserved degradation process of cytoplasmic cellular constituents, associated with cell response to stresses such as hypoxia in cancer microenvironment [ 97 ]. As a key component and a marker of autophagy, LC3 expression in PC tissue significantly correlates with a poor outcome [ 98 ].…”

microRNA-200c-3p suppresses proliferation and invasion of nephroblastoma cells by targeting EP300 and inactivating the AKT/FOXO1/p27 pathway

“…Histone acetyltransferase E1A-binding protein p300 (EP300) is a ubiquitously expressed pleiotropic multidomain coactivator that catalyzes acetylation of histone and nonhistone proteins [22]. EP300 mutations contribute to an unfavorable phenotype in a number of solid tumors and hematological malignancies and therefore EP300 is often considered as tumor promoter [23]. Pathological studies have shown that EP300 was highly expressed in many tumors.…”