title: Principal component analysis for the comparison of metabolic profiles from human rectal cancer biopsies and colorectal xenografts using high-resolution magic angle spinning 1H magnetic resonance spectroscopy.
abstract: BACKGROUND
  This study was conducted in order to elucidate metabolic differences between human rectal cancer biopsies and colorectal HT29, HCT116 and SW620 xenografts by using high-resolution magnetic angle spinning (MAS) magnetic resonance spectroscopy (MRS) and for determination of the most appropriate human rectal xenograft model for preclinical MR spectroscopy studies. A further aim was to investigate metabolic changes following irradiation of HT29 xenografts.
  
  
  METHODS
  HR MAS MRS of tissue samples from xenografts and rectal biopsies were obtained with a Bruker Avance DRX600 spectrometer and analyzed using principal component analysis (PCA) and partial least square (PLS) regression analysis.
  
  
  CONCLUSIONS
  HR MAS MRS enabled assignment of 27 metabolites. Score plots from PCA of spin-echo and single-pulse spectra revealed separate clusters of the different xenografts and rectal biopsies, reflecting underlying differences in metabolite composition. The loading profile indicated that clustering was mainly based on differences in relative amounts of lipids, lactate and choline-containing compounds, with HT29 exhibiting the metabolic profile most similar to human rectal cancers tissue. Due to high necrotic fractions in the HT29 xenografts, radiation-induced changes were not detected when comparing spectra from untreated and irradiated HT29 xenografts. However, PLS calibration relating spectral data to the necrotic fraction revealed a significant correlation, indicating that necrotic fraction can be assessed from the MR spectra.
authors.affiliation: Department of Medical Physics, Rikshospitalet-Radiumhospitalet Medical Center, 0310 Oslo, Norway. therese@radium.uio.no
authors.forename: Therese
authors.initials: T
authors.lastname: Seierstad
authors.forename: Kathrine
authors.initials: K
authors.lastname: Røe
authors.forename: Beathe
authors.initials: B
authors.lastname: Sitter
authors.forename: Jostein
authors.initials: J
authors.lastname: Halgunset
authors.forename: Kjersti
authors.initials: K
authors.lastname: Flatmark
authors.forename: Anne H
authors.initials: AH
authors.lastname: Ree
authors.forename: Dag Rune
authors.initials: DR
authors.lastname: Olsen
authors.forename: Ingrid S
authors.initials: IS
authors.lastname: Gribbestad
authors.forename: Tone F
authors.initials: TF
authors.lastname: Bathen
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D014408:Biomarkers, Tumor / Q000032:analysis; D001706:Biopsy; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008875:Middle Aged; D025341:Principal Component Analysis / Q000379:methods*; D012004:Rectal Neoplasms / Q000378:metabolism* / Q000473:pathology; D013113:Spin Labels; D023041:Xenograft Model Antitumor Assays
chemical_list: D014408:Biomarkers, Tumor; D013113:Spin Labels