title: Quantifying metabolic heterogeneity in head and neck tumors in real time: 2-DG uptake is highest in hypoxic tumor regions.
abstract: OBJECTIVE
  Intratumoral metabolic heterogeneity may increase the likelihood of treatment failure due to the presence of a subset of resistant tumor cells. Using a head and neck squamous cell carcinoma (HNSCC) xenograft model and a real-time fluorescence imaging approach, we tested the hypothesis that tumors are metabolically heterogeneous, and that tumor hypoxia alters patterns of glucose uptake within the tumor.
  
  
  METHODS
  Cal33 cells were grown as xenograft tumors (n = 16) in nude mice after identification of this cell line's metabolic response to hypoxia. Tumor uptake of fluorescent markers identifying hypoxia, glucose import, or vascularity was imaged simultaneously using fluorescent molecular tomography. The variability of intratumoral 2-deoxyglucose (IR800-2-DG) concentration was used to assess tumor metabolic heterogeneity, which was further investigated using immunohistochemistry for expression of key metabolic enzymes. HNSCC tumors in patients were assessed for intratumoral variability of (18)F-fluorodeoxyglucose ((18)F-FDG) uptake in clinical PET scans.
  
  
  RESULTS
  IR800-2-DG uptake in hypoxic regions of Cal33 tumors was 2.04 times higher compared to the whole tumor (p = 0.0001). IR800-2-DG uptake in tumors containing hypoxic regions was more heterogeneous as compared to tumors lacking a hypoxic signal. Immunohistochemistry staining for HIF-1α, carbonic anhydrase 9, and ATP synthase subunit 5β confirmed xenograft metabolic heterogeneity. We detected heterogeneous (18)F-FDG uptake within patient HNSCC tumors, and the degree of heterogeneity varied amongst tumors.
  
  
  CONCLUSIONS
  Hypoxia is associated with increased intratumoral metabolic heterogeneity. (18)F-FDG PET scans may be used to stratify patients according to the metabolic heterogeneity within their tumors, which could be an indicator of prognosis.
authors.affiliation: Physician Scientist Training Program, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America; Howard Hughes Medical Fellow, Howard Hughes Medical Institute, Bethesda, Maryland, United States of America; Department of Pharmacology & Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Erica C
authors.initials: EC
authors.lastname: Nakajima
authors.affiliation: Department of Radiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Charles
authors.initials: C
authors.lastname: Laymon
authors.affiliation: Department of Radiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Matthew
authors.initials: M
authors.lastname: Oborski
authors.affiliation: Department of Immunology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Weizhou
authors.initials: W
authors.lastname: Hou
authors.affiliation: Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Grandis
authors.affiliation: Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Ferris
authors.affiliation: Department of Radiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: James M
authors.initials: JM
authors.lastname: Mountz
authors.affiliation: Department of Pharmacology & Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Bennett
authors.initials: B
authors.lastname: Van Houten
mesh_terms: D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000378:metabolism*; D015687:Cell Hypoxia / Q000502:physiology*; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D005462:Fluorine Radioisotopes / Q000493:pharmacokinetics; D005947:Glucose / Q000378:metabolism*; D006019:Glycolysis; D006258:Head and Neck Neoplasms / Q000378:metabolism*; D064593:Heterografts; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D051379:Mice; D008819:Mice, Nude; D010085:Oxidative Phosphorylation; D049268:Positron-Emission Tomography
chemical_list: D005456:Fluorescent Dyes; D005462:Fluorine Radioisotopes; D005947:Glucose