title: A liquid chromatography-tandem mass spectrometry-based targeted proteomics approach for the assessment of transferrin receptor levels in breast cancer.
abstract: OBJECTIVE
  Overexpression of human transferrin receptor (TfR) has been described qualitatively in various cancers, including breast cancer. Since TfR is also expressed to some extent under normal physiological conditions, increase of specificity and reproducibility in TfR quantification could improve the early detection and prognostic evaluation of cancers.
  
  
  METHODS
  A LC-MS/MS-based targeted proteomics assay was developed for the determination of TfR in human breast cells and tissue samples.
  
  
  RESULTS
  We selected the tryptic peptide 681VEYHFLSPYVSPK693 as the surrogate peptide for quantification and used a stable isotope-labeled synthetic peptide with this sequence as an internal standard. Quality control data indicated acceptable accuracy and precision. Finally, this assay was successfully applied to the quantitative analysis of TfR in three breast cell lines and 36 matched pairs of breast tissue samples. The experimental values were compared with those obtained from conventional analytical methods, including immunofluorescence microscopy, Western blotting, flow cytometry, and immunohistochemistry.
  
  
  CONCLUSIONS
  Not only is the LC-MS/MS-based targeted proteomics assay a more accurate method for the determination of TfR levels, but may afford more reliable quantification of TfR at low concentrations in clinical practice.
authors.affiliation: School of Pharmacy, Nanjing Medical University, Nanjing, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Yang
authors.forename: Feifei
authors.initials: F
authors.lastname: Xu
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhao
authors.forename: Shui
authors.initials: S
authors.lastname: Wang
authors.forename: Mi
authors.initials: M
authors.lastname: Yang
authors.forename: Yun
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D002853:Chromatography, Liquid / Q000379:methods*; D005260:Female; D006801:Humans; D008969:Molecular Sequence Data; D040901:Proteomics; D011990:Receptors, Transferrin / Q000737:chemistry / Q000378:metabolism*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D011990:Receptors, Transferrin
keywords: Breast cancer cells and tissue; Human transferrin receptor; Liquid chromatography-tandem mass spectrometry; Method development; Targeted proteomics