Figure 3. P-gp upregulation by hypoxia results in resistance to bortezomib and carfilzomib.

(A) Cell survival of MM cell lines (OPM2, H929, MM.1S and U266) treated with and without bortezomib (5nM) or (B) carfilzomib (5nM) for 24 hours in normoxic and hypoxic conditions using a MTT assay normalized to untreated (untr) cells. (C) P-gp expression in MM cells treated with bortezomib (5nM) or (D) carfilzomib (5nM) shown as a fold change of P-gp normalized to isotype control and relative to normoxic cells measured by flow cytometry and demonstrated as average from three MM cell lines (H929, MM.1S and U266). Results are shown as mean ± standard deviation (s.d.); the statistical significance was assessed by student t-test and considered significant for values * p<0.05, ** p<0.01 and *** p<0.001.