Chemicals and materials

Exemestane (EXE) and creatinine were purchased from Sigma-Aldrich (St Louis, Missouri, USA). 17β-hydroxy (OH)-EXE-17-O-β-D-Glucuronide (17β-DHE-Gluc), 17β-OH-EXE-D₃-17-O-β-D-Glucuronide (D3-17β-DHE-Gluc), 17β-OH-EXE-d3 (D₃-17β-DHE), EXE-19-D₃ (D₃-EXE), and D₃-creatinine were purchased from Toronto Research Chemicals (North York, ON, Canada). 17β-DHE was synthesized as previously described to a purity of greater than 99% (25). Ammonium formate was obtained from Sigma-Aldrich (St Louis, Missouri, USA) while ammonium acetate and formic acid were purchased from Thermo Fisher Scientific (Waltham, MA, USA). Acetonitrile was purchased from Merck (Kenilworth, NJ, USA). Solvent and buffer modifiers for liquid chromatography-mass spectrometry (LC/MS) analysis including acetonitrile, ammonium formate, ammonium acetate and formic acid were all LC/MS grade. Milli-Q water was used for making any solutions when needed. PureLink ® Genomic DNA Kits were purchased from Thermo Fisher Scientific (Waltham, MA, USA), and the TaqMan® Copy Number Reference Assay (RNase P, Human) and the UGT2B17 TaqMan® Copy Number Assay were purchased from Life Technologies (Carlsbad, CA, USA).