Alpha-Enolase Knockdown Reprograms Metabolism And Points Out Targetable Pathways To Counteract Pda Growth

Pancreatic ductal adenocarcinoma (PDA), an aggressively invasive, treatment-resistant malignancy, is usually detectable only when already inevitably fatal. Despite advances in genetic screening, mapping and molecular characterization, its pathology remains largely elusive. Renewed interest in longstanding doctrines of tumor metabolism has led to the emergence of aberrant signaling pathways as critical factors modulating central metabolic networks that fuel pancreatic tumors. We have previously described α-enolase (ENO1) as a PDA-associated antigen. It is a moonlighting protein that works both as a key metabolic enzyme and a membrane plasminogen receptor. To better characterize ENO1 metabolic and fuelling role in pancreatic cancer, we have silenced ENO1 in three different human PDA cell lines (CFPAC-1, PT45 and T3M4) and evaluated its impact through proteomic, biochemical and functional approaches. Protein expression alterations following ENO1 knockdown were revealed by LC-MS/MS analysis. On the basis of a spectra count label-free quantitation approach several proteins mainly involved in cell adhesion, metabolism and proliferation were found to be differentially expressed in ENO1-silenced cells compared to the control. Indeed, ENO1-silenced PDA cells displayed a delay in proliferation, decreased survival and colony formation capabilities. The cell-cycle profile analysis revealed a strong increase in the number of PDA cells in G2/M phase, a concomitant decrease in G1 phase and no difference in the proportion of cells in S phase after ENO1 silencing as compared to control cells. Moreover, ENO1-silenced cells showed specific morphological changes that were indicative of cellular senescence, as confirmed by an increase in β-galactosidase staining. Of note, ENO1 knockdown PDA cells grew significantly less compared to control cells when injected sub cute in SCID-beige mice. The growth inhibition was partially due to an increased concentration of intracellular reactive oxygen species (ROS) mainly generated through the sorbitol and NADPH oxidase pathways. ENO1 knockdown increase autophagy, the most important stress response for cells to adapt to nutrient starvation and promotes also catabolic pathway adaptations that restore pyruvate and acetyl-CoA bulk. Furthermore, the increased entry of glutamine into the TCA cycle induce a drop in nucleotide bases synthesis and promote oxidative phosphorylation in PDA cells, switching to the aerobic glycolysis typical of cancer cells. These findings may have implications for future therapeutic approaches: the inhibition of ENO1, in fact, can potentially synergize with therapies targeting autophagy and glutamine pathway. Citation Format: Michela Capello, Sammy Ferri-Borgogno, Moitza Principe, Michelle Samuel Chattaragada, Chiara Riganti, Weidong Zhou, Laura Follia, Lance A. Liotta, Emanuel F. Petricoin, III, Paola Cappello, Francesco Novelli. Alpha-enolase knockdown reprograms metabolism and points out targetable pathways to counteract PDA growth. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr B49.