Simultaneous Hypoxia and Low Extracellular pH Suppress Overall Metabolic Rate and Protein Synthesis In Vitro

PLoS One. 2015 Aug 14;10(8):e0134955. doi: 10.1371/journal.pone.0134955. eCollection 2015.


Background: The tumor microenvironment is characterized by regions of hypoxia and acidosis which are linked to poor prognosis. This occurs due to an aberrant vasculature as well as high rates of glycolysis and lactate production in tumor cells even in the presence of oxygen (the Warburg effect), which weakens the spatial linkage between hypoxia and acidosis.

Methods: Five different human squamous cell carcinoma cell lines (SiHa, FaDuDD, UTSCC5, UTSCC14 and UTSCC15) were treated with hypoxia, acidosis (pH 6.3), or a combination, and gene expression analyzed using microarray. SiHa and FaDuDD were chosen for further characterization of cell energetics and protein synthesis. Total cellular ATP turnover and relative glycolytic dependency was determined by simultaneous measurements of oxygen consumption and lactate synthesis rates and total protein synthesis was determined by autoradiographic quantification of the incorporation of 35S-labelled methionine and cysteine into protein.

Results: Microarray analysis allowed differentiation between genes induced at low oxygen only at normal extracellular pH (pHe), genes induced at low oxygen at both normal and low pHe, and genes induced at low pHe independent of oxygen concentration. Several genes were found to be upregulated by acidosis independent of oxygenation. Acidosis resulted in a more wide-scale change in gene expression profiles than hypoxia including upregulation of genes involved in the translation process, for example Eukaryotic translation initiation factor 4A, isoform 2 (EIF4A2), and Ribosomal protein L37 (RPL37). Acidosis suppressed overall ATP turnover and protein synthesis by 50%. Protein synthesis, but not total ATP production, was also suppressed under hypoxic conditions. A dramatic decrease in ATP turnover (SiHa) and protein synthesis (both cell lines) was observed when hypoxia and low pHe were combined.

Conclusions: We demonstrate here that the influence of hypoxia and acidosis causes different responses, both in gene expression and in de novo protein synthesis, depending on whether the two factors induced alone or overlapping, and as such it is important for in vivo studies to take this into account.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acidosis / genetics
  • Acidosis / metabolism
  • Acidosis / pathology
  • Basal Metabolism* / genetics
  • Carcinoma, Squamous Cell / genetics
  • Carcinoma, Squamous Cell / metabolism*
  • Carcinoma, Squamous Cell / pathology
  • Cell Hypoxia / genetics
  • Cell Hypoxia / physiology
  • Cell Line, Tumor
  • Extracellular Space
  • Gene Expression Profiling
  • Gene Expression Regulation, Neoplastic / drug effects
  • Glycolysis / drug effects
  • Glycolysis / genetics
  • Humans
  • Hydrogen-Ion Concentration
  • Microarray Analysis
  • Oxygen / metabolism
  • Oxygen / pharmacology
  • Protein Biosynthesis* / genetics


  • Oxygen

Associated data

  • GEO/GSE70051

Grant support

Financial support was received from the Danish Cancer Society (R72-A4448-13-S2), EC FP7 project METOXIA (project no. 222741), CIRRO - The Lundbeck Foundation Center for Interventional Research in Radiation Oncology (R25-A2703) and The Danish Council for Strategic Research (0603-00136B). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.