Epigenetic loss of the endoplasmic reticulum–associated degradation inhibitor SVIP induces cancer cell metabolic reprogramming
Pere Llinàs-Arias, … , Catia Moutinho, Manel Esteller
Pere Llinàs-Arias, … , Catia Moutinho, Manel Esteller
Published March 7, 2019
Citation Information: JCI Insight. 2019;4(8):e125888. https://doi.org/10.1172/jci.insight.125888.
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Research Article Oncology

Epigenetic loss of the endoplasmic reticulum–associated degradation inhibitor SVIP induces cancer cell metabolic reprogramming

Abstract

The endoplasmic reticulum (ER) of cancer cells needs to adapt to the enhanced proteotoxic stress associated with the accumulation of unfolded, misfolded, and transformation-associated proteins. One way by which tumors thrive in the context of ER stress is by promoting ER-associated degradation (ERAD), although the mechanisms are poorly understood. Here, we show that the small p97/VCP-interacting protein (SVIP), an endogenous inhibitor of ERAD, undergoes DNA hypermethylation–associated silencing in tumorigenesis to achieve this goal. SVIP exhibits tumor suppressor features and its recovery is associated with increased ER stress and growth inhibition. Proteomic and metabolomic analyses show that cancer cells with epigenetic loss of SVIP are depleted in mitochondrial enzymes and oxidative respiration activity. This phenotype is reverted upon SVIP restoration. The dependence of SVIP-hypermethylated cancer cells on aerobic glycolysis and glucose was also associated with sensitivity to an inhibitor of the glucose transporter GLUT1. This could be relevant to the management of tumors carrying SVIP epigenetic loss, because these occur in high-risk patients who manifest poor clinical outcomes. Overall, our study provides insights into how epigenetics helps deal with ER stress and how SVIP epigenetic loss in cancer may be amenable to therapies that target glucose transporters.

Authors

Pere Llinàs-Arias, Margalida Rosselló-Tortella, Paula López-Serra, Montserrat Pérez-Salvia, Fernando Setién, Silvia Marin, Juan P. Muñoz, Alexandra Junza, Jordi Capellades, María E. Calleja-Cervantes, Humberto J. Ferreira, Manuel Castro de Moura, Marina Srbic, Anna Martínez-Cardús, Carolina de la Torre, Alberto Villanueva, Marta Cascante, Oscar Yanes, Antonio Zorzano, Catia Moutinho, Manel Esteller

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Figure 5

Restoration of SVIP expression in transformed cells shifts an aerobic glycolysis phenotype to homeostatic mitochondrial metabolism.

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Restoration of SVIP expression in transformed cells shifts an aerobic gl...
Enzymatic determination of (A) glucose uptake and (B) lactate release normalized with respect to protein concentration in empty vector– and SVIP-transfected BB30-HNC cells. Graphs are representative of 3 independent experiments. Data were analyzed through 2-tailed Student’s t test. (C) Oxygen consumption rate (OCR) normalized with respect to protein concentration of empty vector– and SVIP-transfected BB30-HNC cells under basal conditions (Basal), after oligomycin treatment (ATP-linked), and after FCCP injection (Maximal OCR). This graph is representative of 2 independent experiments, each with 5 technical replicates. (D) ATP concentration determination in empty vector– and SVIP-transfected BB30-HNC cells. Graph is representative of 3 independent experiments. (E) MitoSox median fluorescence intensity (MFI) was determined by flow cytometry. Nine replicates of 4 independent experiments are plotted. (F) MitoTracker MFI was determined by flow cytometry. Mean ± SD of a representative experiment is shown. (G) 13C-citrate and 13C-succinate isotopologue distribution after 24-hour exposure to 25 mM 13C6-glucose. (H) BB30-HNC cell growth in 5 mM low-glucose medium. Graph is representative of 3 independent experiments. (I) SRB assays to determine cell viability upon the use of Bay-876 (GLUT1 inhibitor) of 4 SVIP-unmethylated and -expressing cell lines (green) against 5 cell lines with SVIP hypermethylation–associated silencing (red). (J) SRB assay shows that empty vector–transfected cells with SVIP epigenetic loss are significantly more sensitive to growth inhibition by Bay-876 treatment than are cancer cells with transfection-mediated recovery of SVIP expression. Graph is representative of 3 independent experiments. Statistical differences were determined by Student’s t test at the highest dose. (K) Growth inhibition of empty vector– and SVIP-transfected BB30-HNC cells in an in vivo subcutaneous mouse model was measured by tumor volume time course (left) and final tumor weight (right). Statistical differences in I and K were determined by adjusting the curves to third-grade polynomial equations followed by the extra sum-of-squares F test. *P < 0.5, **P < 0.01. ns, not significant.