The proteasome inhibitor bortezomib reverses P-glycoprotein-mediated leukemia multi-drug resistance through the NF-κB pathway

Multi-drug resistance (MDR) is one of the obstacles for leukemia therapy, the major cause is an overexpression of P-glycoprotein (P-gp) leading to increased drug efflux. We investigated the reversion of multi-drug resistance and the possible mechanism by which the proteasome inhibitor bortezomib affects the expression of the multi-drug resistance gene mdr1 in the K562/DNR cell line. The drug resistance of the cells and the cellular toxicity of bortezomib were confirmed by MTT. Intracellular drug concentrations and cell apoptosis were detected by flow cytometry. The expression of mdr1 mRNA was examined by fluorescence quantitative PCR. The expression levels of nuclear factor-kappa B (NF-κB), inhibitor of NF-κB (IκB) and P-gp were detected by western blotting, and NF-κB activity was detected by ELISA. DNR-induced apoptosis increased in a dose-dependent manner after adding bortezomib. Bortezomib decreased IκB degradation, decreased NF-κB and NF-κB p65 activity, reduced P-gp/mdr1 mRNA expression, and increased the intracellular DNR concentration in K562/DNR cells in vitro. The bortezomib reversed leukemic multi-drug resistance in a dose-dependent manner as the result of decreasing IκB degradation, thus preventing the translocation of NF-κB into the nucleus and leading the down-regulation of mdr1 and a reduction in P-gp expression. Therefore, the intracellular drug concentration increased, and then apoptosis was induced.