Figure 6.

Western blot analysis of breast cancer resistance protein (BCRP) expression and SN‐38 drug sensitivity in PA/C603X mutants. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis was carried out (a) under reducing conditions with heating at 70°C for 10 min and (b) under non‐reducing conditions with heating at 20°C for 5 min. α‐Tubulin expression was analyzed as a loading control. BCRP was detected using the mouse anti‐BCRP monoclonal antibody BXP‐21. Cellular protein (20 µg) was loaded in each lane. (c) SN‐38 sensitivity of parental PA317, PA/WT, PA/C603D, PA/C603Y, PA/C603S and PA/C603A. Drug sensitivity was examined by cell growth inhibition assays as described in Materials and Methods. All data are representative of the mean values ± SD from triplicate determinations.