Fundamental Role of Pentose Phosphate Pathway within the Endoplasmic Reticulum in Glutamine Addiction of Triple-Negative Breast Cancer Cells

first_pagesettingsOrder Article Reprints Open AccessArticle Fundamental Role of Pentose Phosphate Pathway within the Endoplasmic Reticulum in Glutamine Addiction of Triple-Negative Breast Cancer Cells by Cecilia Marini 1,2,*,+,Vanessa Cossu 2,*,+,Sonia Carta 2ORCID,Elisa Greotti 3,4,5ORCID,Daniela Gaglio 1,6,7,Nadia Bertola 8ORCID,Sabrina Chiesa 2,Silvia Bruno 8,Francesca Vitale 2,Marcella Bonanomi 6,7,9ORCID,Danilo Porro 1,Mattia Riondato 2,Anna Maria Orengo 2,Matteo Bauckneht 2,10ORCID,Silvia Morbelli 2,10,Silvia Ravera 8ORCID andGianmario Sambuceti 2,10ORCID 1 Institute of Molecular Bioimaging and Physiology (IBFM), National Research Council (CNR), 20054 Milan, Italy 2 IRCCS Ospedale Policlinico San Martino, 16132 Genova, Italy 3 Department of Biomedical Sciences, University of Padova, 35131 Padua, Italy 4 Neuroscience Institute, Italian National Research Council (CNR), 35131 Padua, Italy 5 Padova Neuroscience Center (PNC), University of Padova, 35131 Padua, Italy 6 ISBE. IT, Centre of Systems Biology, 20126 Milan, Italy 7 Elixir Infrastructure and NBFC, National Biodiversity Future Center, 90133 Palermo, Italy 8 Department of Experimental Medicine, Human Anatomy, University of Genoa, 16132 Genova, Italy 9 Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy 10 Department of Health Sciences, University of Genoa, 16132 Genova, Italy * Authors to whom correspondence should be addressed. + These authors contributed equally to this work. Antioxidants 2023, 12(1), 43; https://doi.org/10.3390/antiox12010043 Received: 15 November 2022 / Revised: 16 December 2022 / Accepted: 21 December 2022 / Published: 26 December 2022 Download Browse Figures Versions Notes Abstract Cancer utilization of large glutamine equivalents contributes to diverging glucose-6-P flux toward the pentose phosphate shunt (PPP) to feed the building blocks and the antioxidant responses of rapidly proliferating cells. In addition to the well-acknowledged cytosolic pathway, cancer cells also run a largely independent PPP, triggered by hexose-6P-dehydrogenase within the endoplasmic reticulum (ER), whose activity is mandatory for the integrity of ER-mitochondria networking. To verify whether this reticular metabolism is dependent on glutamine levels, we complemented the metabolomic characterization of intermediates of the glucose metabolism and tricarboxylic acid cycle with the estimation of proliferating activity, energy metabolism, redox damage, and mitochondrial function in two breast cancer cell lines. ER-PPP activity and its determinants were estimated by the ER accumulation of glucose analogs. Glutamine shortage decreased the proliferation rate despite increased ATP and NADH levels. It depleted NADPH reductive power and increased malondialdehyde content despite a marked increase in glucose-6P-dehydrogenase. This paradox was explained by the deceleration of ER-PPP favored by the decrease in hexose-6P-dehydrogenase expression coupled with the opposite response of its competitor enzyme glucose-6P-phosphatase. The decreased ER-PPP activity eventually hampered mitochondrial function and calcium exchanges. These data configure the ER-PPP as a powerful, unrecognized regulator of cancer cell metabolism and proliferation.