title: Absolute quantification of choline-related biomarkers in breast cancer biopsies by liquid chromatography electrospray ionization mass spectrometry.
abstract: It has been repeatedly demonstrated that choline metabolism is altered in a wide variety of cancers. In breast tumours, the choline metabolite profile is characterized by an elevation of phosphocholine and total choline-compounds. This pattern is increasingly being exploited as biomarker in cancer diagnosis. The majority of in vitro metabolomics studies, for biomarkers quantification in cell cultures or tissues, entail proton NMR spectroscopy. Although many "targeted" approaches have been proposed to quantify metabolites from standard one-dimensional (1D) NMR experiments, the task is often made difficult by the high degree of overlap characterizing 1H NMR spectra of biological samples. Here we present an optimized protocol for tissue extraction and absolute quantification of choline, phosphocholine and glycerophosphocholine by means of liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS). The selected chromatographic separation system with a HILIC (hydrophilic interaction chromatography) amide column effectively separates free choline and its phopshorylated derivatives, contrary to failure observed using standard reversed-phase chromatography. The metabolite absolute quantification is based on external calibration with commercial standards, and is validated by a parallel 1D proton NMR analysis. The LC-MS/NMR analysis is applied to three breast carcinoma specimens obtained by surgical excision, each one accompanied by a control tissue sample taken outside the tumor margin. The metabolite concentrations measured are in good agreement with previous results on metabolic profile changes of breast cancer. Each of the three cancerous biopsies, when compared with the control tissue, exhibit a highly increased levels phosphocholine, total choline and phosphocholine/glycerophosphocholine ratio.
authors.affiliation: Department of Medical and Biological Sciences, University of Udine, Piazzale M. Kolbe, Udine, Italy.
authors.forename: Maria Chiara
authors.initials: MC
authors.lastname: Mimmi
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Finato
authors.forename: Gloria
authors.initials: G
authors.lastname: Pizzolato
authors.forename: Carlo Alberto
authors.initials: CA
authors.lastname: Beltrami
authors.forename: Federico
authors.initials: F
authors.lastname: Fogolari
authors.forename: Alessandra
authors.initials: A
authors.lastname: Corazza
authors.forename: Gennaro
authors.initials: G
authors.lastname: Esposito
mesh_terms: D000097:Acetonitriles; D014408:Biomarkers, Tumor / Q000032:analysis*; D001706:Biopsy; D001940:Breast / Q000737:chemistry; D001943:Breast Neoplasms / Q000737:chemistry* / Q000378:metabolism / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000737:chemistry* / Q000378:metabolism / Q000473:pathology; D018275:Carcinoma, Lobular / Q000737:chemistry* / Q000378:metabolism / Q000473:pathology; D002794:Choline / Q000032:analysis* / Q000302:isolation & purification / Q000378:metabolism; D002853:Chromatography, Liquid / Q000379:methods*; D005260:Female; D005997:Glycerylphosphorylcholine / Q000032:analysis* / Q000302:isolation & purification; D006801:Humans; D055432:Metabolomics / Q000379:methods; D019906:Nuclear Magnetic Resonance, Biomolecular; D010767:Phosphorylcholine / Q000032:analysis* / Q000302:isolation & purification; D012997:Solvents; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D000097:Acetonitriles; D014408:Biomarkers, Tumor; D012997:Solvents; D010767:Phosphorylcholine; D005997:Glycerylphosphorylcholine; D002794:Choline; C032159:acetonitrile
keywords: $^1$H-NMR; LC–ESI-MS; Metabolomics; breast cancer; choline phospholipid metabolism; hydrophilic interaction chromatography