title: A liquid chromatography-tandem mass spectrometry-based targeted proteomics assay for monitoring P-glycoprotein levels in human breast tissue.
abstract: BACKGROUND
  P-glycoprotein (P-gp) can efflux drugs from cancer cells, and its overexpression is commonly associated with multi-drug resistance (MDR). Thus, the accurate quantification of P-gp would help predict the response to chemotherapy and for prognosis of breast cancer patients.
  
  
  METHODS
  An advanced liquid chromatography-tandem mass spectrometry (LC/MS/MS)-based targeted proteomics assay was developed and validated for monitoring P-gp levels in breast tissue.
  
  
  RESULTS
  Tryptic peptide 368IIDNKPSIDSYSK380 was selected as a surrogate analyte for quantification, and immuno-depleted tissue extract was used as a surrogate matrix. Matched pairs of breast tissue samples from 60 patients who were suspected to have drug resistance were subject to analysis. The levels of P-gp were quantified. Using data from normal tissue, we suggested a P-gp reference interval. The experimental values of tumor tissue samples were compared with those obtained from Western blotting and immunohistochemistry (IHC). The result indicated that the targeted proteomics approach was comparable to IHC but provided a lower limit of quantification (LOQ) and could afford more reliable results at low concentrations than the other two methods.
  
  
  CONCLUSIONS
  LC/MS/MS-based targeted proteomics may allow the quantification of P-gp in breast tissue in a more accurate manner.
authors: Nanjing Medical University, Nanjing 211166, China.
authors: Ting
authors: T
authors: Yang
authors: Department of Breast Surgery, Nanjing Maternity and Child Health Care Hospital, Nanjing 210004, China.
authors: Fei
authors: F
authors: Chen
authors: Nanjing Medical University, Nanjing 211166, China.
authors: Feifei
authors: F
authors: Xu
authors: Department of Breast Surgery, Nanjing Maternity and Child Health Care Hospital, Nanjing 210004, China.
authors: Fengliang
authors: F
authors: Wang
authors: Nanjing Medical University, Nanjing 211166, China.
authors: Qingqing
authors: Q
authors: Xu
authors: Nanjing Medical University, Nanjing 211166, China. Electronic address: ychen@njmu.edu.cn.
authors: Yun
authors: Y
authors: Chen
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry / Q000378:metabolism*; D000328:Adult; D000595:Amino Acid Sequence; D001940:Breast / Q000378:metabolism* / Q000473:pathology; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D002853:Chromatography, Liquid / Q000379:methods*; D019008:Drug Resistance, Neoplasm; D005260:Female; D006801:Humans; D008875:Middle Aged; D059748:Proteolysis; D040901:Proteomics / Q000379:methods*; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1
keywords: Breast tissue; Liquid chromatography–tandem mass spectrometry; Method comparison; Multiple reaction monitoring; P-glycoprotein; Targeted proteomics