Fig. 6.

Inhibition of CK2 in HeLa, H460, and A549 cancer cell lines results in decreased MRP1-dependent doxorubicin efflux. A, Western blot showing expression of MRP1, ABCB1, ABCGw2, and CK2α proteins in HeLa, H460, A549, and MCF7 (WT) and MCF7/MRP1 (MRP1) cell lines. In lane 1, ABCB1-expressing cell line was loaded as a positive control for immunoblotting of ABCB1. B, doxorubicin accumulation assays were performed as described under Materials and Methods. Where indicated, cells were pretreated with 50 μM MK571, 40 μM TBBz, 10 μM FTC, or 1 μM PSC883 for 1 h before the addition of doxorubicin. Experiments were performed in triplicate, and results were presented as mean values ± S.D. Statistical analysis was performed using one-way ANOVA followed by Bonferroni post-test. C, cytotoxicity profiles of doxorubicin were determined by MTT assay as described under Materials and Methods. Points represent mean values ± 95% confidence intervals of two or three separate experiments performed with repeated measures in 96-well plates. The data were normalized to the baseline absorbance, and four-parameter logistic nonlinear regression curves were generated with use of GraphPad Prism 5. Summary statistics derived from these data are listed in Table 2.