Figure 4. P-gp inhibition using tariquidar decreases P-gp activity and restores drug sensitivity.
(A) Intracellular RhoB content in MM cells treated with tariquidar (5μM) in normoxia and hypoxia for 24 hours measured by flow cytometry and depicted as (A) MFI normalized to unstained cells, relative to normoxic untreated (untr), averaged from 3 cells lines (H929, MM.1S and U266) or (B) histograms demonstrating RhoB efflux in individual cell lines. (C) Cell survival study of MM.1S cells treated with bortezomib (5nM) or (D) carfilzomib (5nM), in the presence or absence of tariquidar (5μM) or their combination, for 24 hours in normoxia and hypoxia using MTT assay normalized to untreated (untr) MM.1S cells. Results are shown as mean ± s.d. and the statistical significance was assessed by student t-test and considered significant for values * p<0.05, ** p<0.01 and *** p<0.001.