Evaluation of Novel Diaza Cage Compounds as MRP Modulators in Cancer Cells

Aim: Novel MRP modulators are needed to combat MRP-mediated multidrug resistance (MDR) in cancer cells. Background: Anticancer drug resistance is the main problem in cancer therapy. Causative multidrug efflux pumps are attractive target structures for the development of inhibitors of their activity. Objective: We synthesized novel cage dimeric 1,4-dihydropyridines to evaluate them as MRP modulators in cancer cells targeting MRP1, MRP2, and MRP4. Method: Cage compounds were synthesized by solution dimerization of monomeric 1,4-dihydropyridines and a final functionalization reaction. The MRP modulation was determined in cellular efflux assays by the use of the flow cytometry technique as well as cellular fluorescent measurements with each fluorescent substrate of the efflux pumps. Results: Difluoro phenyl and methoxy or dimethoxy benzyl substitutions were most favourable for the MRP1 and MRP2 inhibition, whereas monofluor phenyl and dimethoxy benzyl substitutions were most favourable for the MRP4 inhibition. Conclusion: Effective inhibitors were identified that were demonstrated to restore the respective cancer cell line sensitivity for the anticancer drug as a proof-of-concept that encourages further preclinical studies.