Piperine pip

Piperine (PIP, purity >97%) and glibenclamide were obtained from Sigma-Aldrich Chemical Co. (Milwaukee, WI, USA). Docetaxel (DTX, purity >99 %) was purchased from Chongqing Taihao Pharmaceutical Co. Ltd (Chongqing, China). Acetonitrile (Labscan Asia, Thailand) and methanol (TEDIA Co., Inc., USA) were in HPLC grade and used without further purification. Distilled and deionized water was prepared from Millipore Water Purification System (Millipore, Milford, USA). All other reagents were of at least analytical grade.
A taxane-resistant human prostate cancer cell line (PC3-TxR cells) was provided by Department of Medicine, University of Michigan (Ann Arbor, MI, USA). It was established based on the method of Takeda et al. [43 (link)]. The human prostate cancer cell line (PC3 cells) was a gift from Professor Moses S. S. Chow (Center for Advanced Drug Research and Evaluation, College of Pharmacy, Western University of Health Sciences, USA). MDCK cell line transfected with human MDR1 gene (MDCK/MDR1) was a kind gift from Prof. P. Borst (The Netherlands Cancer Institute, Amsterdam, Netherlands).

Piperine (PIP) (purity ≥ 97%) was purchased from Sigma-Aldrich having cat no- P49007-1G. For cell culture experiments, PIP was dissolved in molecular grade dimethylsulfoxide (DMSO) in a stock solution of 20 mM. For mouse experiments, PIP was freshly formulated as 60 mg/mL and 6 mg/mL in vehicle (0.2% DMSO + one drop tween-80 in sterile PBS). All the other chemicals used are of an analytical grade and were purchased from Sigma Aldrich (USA), Thermo Scientific (USA) etc.