title: Metabolomic analysis identifies differentially produced oral metabolites, including the oncometabolite 2-hydroxyglutarate, in patients with head and neck squamous cell carcinoma.
abstract: BACKGROUND
  Metabolomics represents a promising approach for discovering novel targets and biomarkers in head and neck squamous cell carcinoma (HNSCC). Here we used metabolomics to identify oral metabolites associated with HNSCC.
  
  
  METHODS
  Tumor and adjacent normal tissue from surgical resections and presurgical oral washes as well as oral washes were collected from healthy participants. Metabolites extractions of these samples were analyzed by liquid chromatography-mass spectroscopy (LC/MS), LC/MS/MS and gas chromatography-MS (GC/MS).
  
  
  RESULTS
  Among 28 samples obtained from 7 HNSCC cases and 7 controls, 422 metabolites were detected (269 identified and 153 unidentified). Oral washes contained 12 and 23 metabolites in healthy controls and HNSCC patients, respectively, with phosphate and lactate being the most abundant. Small molecules related to energy metabolism were significantly elevated in HNSCC patients compared to controls. Levels of beta-alanine, alpha-hydroxyisovalerate, tryptophan, and hexanoylcarnitine were elevated in HNSCC oral washes compared to healthy controls (range 7.8-12.2-fold). Resection tissues contained 22 metabolites, of which eight were overproduced in tumor by 1.9- to 12-fold compared to controls. TCA cycle analogs 2-hydroxyglutarate(2-HG) and 3-GMP were detected exclusively in tumor tissues. Targeted quantification of 2-HG in a representative HNSCC patient showed increase in tumor tissue (14.7 μg/mL), but undetectable in normal tissue. Moreover, high levels of 2-HG were detected in HNSCC cell lines but not in healthy primary oral keratinocyte cultures.
  
  
  CONCLUSIONS
  Oral metabolites related to energy metabolism were elevated in HNSCC, and acylcarnitine and 2HG may have potential as non-invasive biomarkers. Further validation in clinical studies is warranted.
authors.affiliation: Center for Medical Mycology, Department of Dermatology, Case Western Reserve University, University Hospitals Case Medical Center, Cleveland, OH, United States.
authors.forename: Pranab K
authors.initials: PK
authors.lastname: Mukherjee
authors.affiliation: Genomic Medicine Institute, Lerner Research Institute, Taussig Cancer Institute, United States.
authors.forename: Pauline
authors.initials: P
authors.lastname: Funchain
authors.affiliation: Center for Medical Mycology, Department of Dermatology, Case Western Reserve University, University Hospitals Case Medical Center, Cleveland, OH, United States.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Retuerto
authors.affiliation: Diagnostic Sciences, School of Dentistry, West Virginia University, Morgantown, WV, United States.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Jurevic
authors.affiliation: Department of Otolaryngology Cleveland, OH.
authors.forename: Nicole
authors.initials: N
authors.lastname: Fowler
authors.affiliation: Head and Neck Institute, Cleveland Clinic, Cleveland, OH, United States.
authors.forename: Brian
authors.initials: B
authors.lastname: Burkey
authors.affiliation: Genomic Medicine Institute, Lerner Research Institute, Taussig Cancer Institute, United States; Department of Genetics and Genome Sciences, Cleveland, OH, United States; Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH, United States.
authors.forename: Charis
authors.initials: C
authors.lastname: Eng
authors.affiliation: Center for Medical Mycology, Department of Dermatology, Case Western Reserve University, University Hospitals Case Medical Center, Cleveland, OH, United States.
authors.forename: Mahmoud A
authors.initials: MA
authors.lastname: Ghannoum
keywords: 2-Hydroxyglutarate; Biomarker; HNSCC; Hexanoylcarnitine; Metabolomics