Identification of Food-Derived Isoflavone Sulfates as Inhibition Markers for Intestinal Breast Cancer Resistance Proteins.

Potential inhibition of the breast cancer resistance protein (BCRP), a drug efflux transporter, is a key issue during drug development, and the use of its physiologic substrates as biomarkers can be advantageous to assess inhibition. In this study, we aimed to identify BCRP substrates by an untargeted metabolomic approach. Mice were orally administered lapatinib to inhibit BCRP in vivo, and plasma samples were assessed by liquid chromatography/time of flight/mass spectrometry with all-ion fragmentation acquisition and quantified by liquid chromatography with tandem mass spectrometry.