Calu-3 and NHBE cell

layers were harvested from Transwell® inserts on the same day as 3H-digoxin permeability experiments. mRNA isolation and cDNA synthesis were performed as described previously [26]. Manual TaqMan® analysis of the ABCC7 and ABCC10-12 genes was performed in triplicate in a 25 μl reaction mixture containing 30 ng cDNA, TaqMan® Universal PCR Master Mix (containing AmpliTaq Gold DNA polymerase, dNTPs with dUTP, passive reference and optimised buffer) and Assay-on-demand™ gene expression assay mix (containing 18 μM random hexamer primers). All other genes investigated were analysed via automated Taqman® PCR low density arrays using custom designed 384-well cards as described previously [26]. Amplification curves DNA Damage inhibitor were analysed using the SDS2.1 software (Applied Biosystems, Foster City, CA) and thresholds for generation of Regorafenib manufacturer C  T data were calculated automatically by the software. Target genes were compared with the two house-keeping genes RPLP0 (Large Ribosomal Protein) and MVP (Major Vault Protein) ΔC  T and assigned arbitrary categories for relative gene expression levels based on the 2T-ΔC value, i.e. relative expression levels >0.5 were considered as ‘high’ (+++), 0.02–0.5 as ‘moderate’ (++), 0.001–0.02 as ‘low’ (+) and <0.001

as ‘negligible’ (−). Cells were detached from the surface of the filters/flasks by the addition of 500 μl non-enzymatic cell dissociation buffer prepared in HBSS without calcium and magnesium salts. Cells were counted and resuspended in RIPA cell lysis buffer containing 1 μl of protease inhibitor cocktail set II per 200 μl (ratio of 20 million cells per 1 ml buffer solution) and agitated at 700 rpm at 4 °C for 30 min. Cell debris was pelleted at room temperature by centrifugation at 12,000g for 20 min and the resulting supernatant decanted. Protein concentration was quantified using the RC DC™ protein assay (BioRad, Hemel Hempstead,

Hertfordshire). Protein samples were resolved using 7% Tris–acrylamide gels. Briefly, 10 μl of cell lysate solution containing 20–30 μg the of protein was diluted 1:1 with reducing sample buffer. Samples were run under denatured and reduced conditions alongside 5 μl precision plus protein standards (BioRad, Hemel Hempstead, UK) and resolved at 0.04 amps in running buffer. Transfer to a nitrocellulose membrane was conducted for 60 min at 100 V and at a temperature of 4 °C. Proteins transferred onto Western blots were visualised by staining with copper phthalocyanine 3,4′,4″,4″′-tetrasulphonic acid tetrasodium salt (CPTA). Samples were probed for the presence of MDR1 protein using 5 μg/ml of the mouse anti P-glycoprotein C219 primary antibody (Calbiochem, Nottingham, UK) for 16 h at 4 °C. All steps were performed using a chemiluminescence detection kit according to the manufacturer’s instructions (Invitrogen, Paisley, UK).