title: Quantitative assessment of human serum transferrin receptor in breast cancer patients pre- and post-chemotherapy using peptide immunoaffinity enrichment coupled with targeted proteomics.
abstract: BACKGROUND
  sTfR, a soluble form of transferrin receptor in serum, has been suggested as an indicator of bone marrow failure in breast cancer patients receiving chemotherapy. However, intensive chemotherapy could also cause a reduction of sTfR to a level below the LOQ of most assays.
  
  
  METHODS
  An advanced liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based targeted proteomics assay coupled with peptide immunoaffinity enrichment (SISCAPA) was developed and validated for monitoring sTfR.
  
  
  RESULTS
  Tryptic peptide 681VEYHFLSPYVSPK693 was selected as a surrogate analyte for quantification. High-abundant proteins were first removed from serum, followed by SISCAPA that was effective in surrogate peptide enrichment and sensitivity enhancement. The resulting LOQ can achieve 100ng/ml (~10-fold increase). Then, sTfR levels in breast cancer patients pre- and post-chemotherapy, and healthy volunteers were accurately quantified as 1.77±0.53μg/ml, 0.98±0.26μg/ml and 1.66±0.50μg/ml, respectively, using a standard addition method. While there was no evidence for a difference between patients and healthy volunteers, differential levels of sTfR pre- and post-chemotherapy were obtained. Comparison between SISCAPA-targeted proteomics and ELISA indicated that the former approach provided a lower value of sTfR.
  
  
  CONCLUSIONS
  SISCAPA-targeted proteomics may allow the quantification of low-abundant proteins in a more accurate manner.
authors.affiliation: Nanjing Medical University, Nanjing, 211166, China.
authors.forename: Qingqing
authors.initials: Q
authors.lastname: Xu
authors.affiliation: Jiangsu Cancer Hospital, Nanjing, China.
authors.forename: Mingchen
authors.initials: M
authors.lastname: Zhu
authors.affiliation: Nanjing Medical University, Nanjing, 211166, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Yang
authors.affiliation: Nanjing Medical University, Nanjing, 211166, China.
authors.forename: Feifei
authors.initials: F
authors.lastname: Xu
authors.affiliation: First Affiliated Hospital of Nanjing Medical University, Nanjing, 210006, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Nanjing Medical University, Nanjing, 211166, China. Electronic address: ychen@njmu.edu.cn.
authors.forename: Yun
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000097:blood* / Q000188:drug therapy*; D002853:Chromatography, Liquid; D005260:Female; D006801:Humans; D008875:Middle Aged; D010455:Peptides / Q000097:blood / Q000276:immunology*; D040901:Proteomics; D011990:Receptors, Transferrin / Q000097:blood* / Q000276:immunology*; D053719:Tandem Mass Spectrometry
chemical_list: D010455:Peptides; D011990:Receptors, Transferrin
keywords: Breast cancer; Chemotherapy; Liquid chromatography-tandem mass spectrometry; SISCAPA; Serum transferrin receptor; Targeted proteomics