The International Journal of Biochemistry & Cell Biology 42 (2010) 1744–1751 Contents lists available at ScienceDirect The International Journal of Biochemistry & Cell Biology journal homepage: www.elsevier.com/locate/biocel Oxidative phosphorylation is impaired by prolonged hypoxia in breast and possibly in cervix carcinoma Sara Rodríguez-Enríquez a,∗ , Liliana Carre ˜ no-Fuentes a , Juan Carlos Gallardo-Pérez a , Emma Saavedra a , Héctor Quezada a , Alicia Vega b , Alvaro Marín-Hernández a , Viridiana Olín-Sandoval a , M. Eugenia Torres-Márquez b , Rafael Moreno-Sánchez a a Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chávez, México D.F. 14080, Mexico b Departamento de Bioquímica, Facultad de Medicina, UNAM, México D.F. 04510, Mexico article info Article history: Received 26 March 2010 Received in revised form 18 June 2010 Accepted 12 July 2010 Available online 21 July 2010 Keywords: Glycolysis Hypoxia Mitochondria Oxidative phosphorylation Breast cancer abstract It has been assumed that oxidative phosphorylation (OxPhos) in solid tumors is severely reduced due to cytochrome c oxidase substrate restriction, although the measured extracellular oxygen concentration in hypoxic areas seems not limiting for this activity. To identify alternative hypoxia-induced OxPhos depressing mechanisms, an integral analysis of transcription, translation, enzyme activities and path- way fluxes was performed on glycolysis and OxPhos in HeLa and MCF-7 carcinomas. In both neoplasias exposed to hypoxia, an early transcriptional response was observed after 8 h (two times increased glycolysis-related mRNA synthesis promoted by increased HIF-1 levels). However, major metabolic remodeling was observed only after 24 h hypoxia: increased glycolytic protein content (1–5-times), enzyme activities (2-times) and fluxes (4–6-times). Interestingly, in MCF-7 cells, 24 h hypoxia decreased OxPhos flux (4–6-fold), and 2-oxoglutarate dehydrogenase and glutaminase activities (3-fold), with no changes in respiratory complexes I and IV activities. In contrast, 24 h hypoxia did not significantly affect HeLa OxPhos flux; neither mitochondria related mRNAs, protein contents or enzyme activities, although the enhanced glycolysis became the main ATP supplier. Thus, prolonged hypoxia (a) targeted some mito- chondrial enzymes in MCF-7 but not in HeLa cells, and (b) induced a transition from mitochondrial towards a glycolytic-dependent energy metabolism in both MCF-7 and HeLa carcinomas. © 2010 Elsevier Ltd. All rights reserved. 1. Introduction For growth, solid tumors have developed strategies to main- tain the carbon source and oxygen supplies. Thus, tumors exhibit an active angiogenesis which, however, is highly inefficient gen- erating chaotic networks, with unorganized, fragile, and leaky new vessels (reviewed by Nagy et al., 2009). In consequence, the dynam- ics of the blood flow is affected, leading to hypoxic regions at 100–200 m away from a functional blood supply (Vaupel et al., 1989; Helmlinger et al., 1997; Nagy et al., 2009). It has been determined that the oxygen concentration inside well-oxygenated areas of several carcinomas ranges from 30 to Abbreviations: COX, cytochrome c oxidase; HIF-1, hypoxia-inducible factor 1; HK, hexokinase; GA, glutaminase; OxPhos, oxidative phosphorylation; PDH, pyru- vate dehydrogenase complex; PDK1, pyruvate dehydrogenase kinase-1; 2-OGDH, 2-oxoglutarate dehydrogenase. ∗ Corresponding author at: Departamento de Bioquímica, Instituto Nacional de Cardiología, Juan Badiano No. 1, Col. Sección 16, Tlalpan, México D.F. 14080, Mexico. Tel.: +52 55 55 73 29 11. E-mail address: saren960104@hotmail.com (S. Rodríguez-Enríquez). 80 mm Hg whereas in their hypoxic regions, it may reach a value of 2.5–10 mm Hg (equivalent to 3–13 MO 2 , calculated by Horan and Koch, 2001)(Kallinowski et al., 1989; Vaupel et al., 1991; Hunjan et al., 1998; Erickson et al., 2003). The development of hypoxic regions in solid tumors is a typical characteristic linked to malignant pheno- type, metastasis, chemo-, immuno- and radio-therapy resistance, high genetic instability and apoptosis tolerance (Graeber et al., 1996; Bristow and Hill, 2008). Some of these processes are modu- lated by HIF-1, a key transcriptional factor that regulates the gene transcription of proteins involved in angiogenesis, cellular prolif- eration, erythropoietic and vascularization pathways (Weidemann and Johnson, 2008), allowing tissues to adjust to scarce oxygen availability. At metabolic level, HIF-1 increases the gene tran- scription of specific isoenzymes of almost all glycolytic enzymes and transporters (reviewed in Marín-Hernández et al., 2009); in consequence, the glycolytic flux increases by at least 2-times in the majority of neoplasias (Altenberg and Greulich, 2004; Walenta et al., 2004). In spite of the hypoxic-glycolytic activation, the tumor intracel- lular ATP pool drastically diminishes (30–60%) whereas phosphate augments (Mueller-Klieser et al., 1990; Heerlein et al., 2005; 1357-2725/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocel.2010.07.010