Sensitivity of bortezomib-resistant cell lines to proteasome inhibitors after IFN-y pre-exposure. Sensitivity of 8226/BTZ100, THP1/BTZ200 and CEM BTZ/200 cells to (A) bortezomib (BTZ) (with and without IFN-γ), (B) Carfilzomib (CFZ) (with and without IFN-γ), and (C) ONX 0914 (with and without IFN-γ), compared to parental cell sensitivity, and (D) and the sensitivity of 8226/BTZ7 cells to BTZ, CFZ, and ONX 0914, as determined by MTT cytotoxicity assays after 4 days drug exposure. Pre-exposure with 100 U/ml IFN-y was for 24h prior to 4-day BTZ, CFZ and ONX 0914 addition. Results represent the mean (± SD) of 3 individual experiments. P-values indicate differences between BTZ-resistant cells exposed or unexposed to IFN-γ.