title: The lipid composition of isolated cytoplasmic lipid droplets from a human cancer cell line, BE(2)M17.
abstract: (1)H nuclear magnetic resonance spectroscopy (NMR) resonances from lipids in tumours are associated with tumour grade and treatment response. The origin of these NMR signals is mainly considered to be cytoplasmic lipid droplets (LDs). Techniques exist for isolating LDs but little is known about their composition and its relationship to NMR signals. In this work, density-gradient ultracentrifugation was performed on homogenised human cancer cells to isolate LDs. (1)H NMR was performed on whole cells, isolated LDs and their extracts. Heteronuclear single quantum coherence spectroscopy (HSQC) and liquid chromatography mass spectroscopy (LC-MS) were performed on lipid extracts of LDs. Staining and microscopy were used to characterize isolated LDs. An excellent agreement in chemical shift and relative signal intensity was observed between lipid resonances in cells and isolated LD spectra supporting that NMR-visible lipids originate primarily from LDs. Isolated LDs showed high concentrations of unsaturated lipids, a oleic-to-linoleic acid ratio greater than two and a cholesteryl ester (ChE)-to-cholesterol (Ch) ratio close to unity. These ratios were several-fold greater than respective ratios in whole cells, demonstrating isolation is important to characterize LD composition. LDs contain a specific group of lipid species that are likely to contribute to the (1)H NMR spectrum of cells.
authors.affiliation: Cancer Sciences, Institute of Child Health, University of Birmingham, Birmingham, UK.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Pan
authors.forename: Martin
authors.initials: M
authors.lastname: Wilson
authors.forename: Carmel
authors.initials: C
authors.lastname: McConville
authors.forename: Marie-Anne
authors.initials: MA
authors.lastname: Brundler
authors.forename: Theodoros N
authors.initials: TN
authors.lastname: Arvanitis
authors.forename: John P
authors.initials: JP
authors.lastname: Shockcor
authors.forename: Julian L
authors.initials: JL
authors.lastname: Griffin
authors.forename: Risto A
authors.initials: RA
authors.lastname: Kauppinen
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Peet
mesh_terms: D045744:Cell Line, Tumor; D003593:Cytoplasm / Q000737:chemistry*; D005227:Fatty Acids / Q000032:analysis* / Q000737:chemistry / Q000145:classification; D006801:Humans; D009447:Neuroblastoma / Q000737:chemistry* / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular
chemical_list: D005227:Fatty Acids