Nuclear Transcription Factor Kappa B Downregulation Reduces Chemoresistance in Bone Marrow-derived Cells Through P-glycoprotein Modulation.

Background And Aims: Nuclear transcription factor kappa B (NF-κB) is associated with many types of refractory cancer. However, despite multiple strategies to treat cancer and novel target drugs, multidrug resistance still causes relapses. The best-characterized mechanism responsible for multidrug resistance involves the expression of the MDR-1 gene product, P-glycoprotein (P-gp). Because the direct inhibition of this protein is very toxic, other methods of multidrug resistance (MDR) regulation have been proposed. The MDR-1 promoter sequence contains a κB site, which is recognized by NF-κB. The aim of this work was to characterize whether NF-κB modulation changes the response of bone marrow-derived cells (BMDCs) to chemotherapy.

Results: We exposed BMDCs to etoposide and doxorubicin, two of the most used antineoplastic drugs. BMDCs presented high tolerance to these drugs, which correlated with high intrinsic P-gp activity and strong protein expression of NF-κB. To determine the mechanism behind the poor sensitivity of BMDCs to chemotherapy, we blocked the activity of the heterodimer protein NF-κB using the pharmacological inhibitor Bay 11-7085 and through the transfection of an adenovirus negative mutant of I kappa B alpha. The multidrug resistance phenotype of BMDCs was reversed by inhibiting the NF-κB pathway, and this change was accompanied by a decrease in P-gp activity.

Conclusions: NF-κB is a possible target for improving the antineoplastic response.