Comparison of liquid chromatography-tandem mass spectrometry-based targeted proteomics and conventional analytical methods for the determination of P-glycoprotein in human breast cancer cells.

•A novel and advanced LC/MS/MS-based targeted proteomics assay was developed and validated.•Protein digestion efficiency and membrane extraction recovery were discussed.•The LC/MS/MS assay was compared with the conventional analytical methods.•The LC/MS/MS assay can allow the measurement of the P-gp expression level in a more accurate manner.