Figure 4.

Influence of siRNA-mediated knockdown of ABCB1 in combination with DTX on cellular viability and clonogenic survival of DU145 and PC-3 DTXR cells. (a) The relative transcript and protein levels of ABCB1 in DTXR cells 96 h after siRNA transfection start are depicted. An exemplary Western blot for the detection of ABCB1 protein with GAPDH as reference protein is shown. (b) DU145 and PC-3 DTXR cells were treated with a serial dilution of DTX after transfection with either siR-CON or siR-ABCB1 (20 nM). After treatment, the metabolic activity was measured by the WST-1 assay and IC₅₀ values for DTX were calculated. The adjacent graphs to the right depict IC₅₀ values calculated from individual experiments. (c) DTXR cells were transfected with either siR-CON or siR-ABCB1 (20 nM) and 96 h after transfection start the cells were treated with 50 nM DTX. Thereafter, cell colony formation assays were seeded and cell colonies were counted after 10–12 d. Exemplary colonies are shown in the right panels. All data were normalized to the indicated control (black line). Data are depicted as mean ± SD of three to five independent biological replicates. (a,c) One-sample t-test for comparison to the siR-CON-treated controls and (b,c) non-paired t-test with Welch’s correction for comparison of two treatment groups: * p < 0.05, *** p < 0.001, ns: not significant.