Overcoming multidrug resistance (MDR): design, biological evaluation and molecular modelling studies of 2,4-substituted quinazoline derivatives

Chemosensitizing potential of andrographolide in P-glycoprotein overexpressing multidrug-resistant cancer cell lines

The P-glycoprotein (P-gp) plays a major role in the efflux of chemotherapeutic drugs and significantly limits chemotherapy efficacy. Chemosensitizers augment the therapeutic effects of anticancer agents by overcoming drug resistance mechanisms. In this study, the chemosensitizing property of andrographolide (Andro) in P-gp overexpressing multidrug-resistant (MDR) colchicine-selected KBChR 8-5 cells was evaluated. Molecular docking studies showed Andro exhibits higher binding interaction with P-gp than the other two ABC-transporters studied. Further, it inhibits P-gp transport function in a concentration dependant manner in the colchicine-selected KBChR 8-5 cells. Moreover, Andro downregulates P-gp overexpression via NF-κB signaling in these MDR cell lines. MTT-based cell-based assay illustrates that Andro treatment augments the PTX effect in the KBChR 8-5 cells. Further, the Andro plus PTX combination showed enhanced apoptotic cell death in KBChR 8-5 cells compared with PTX alone treatment. Therefore, the results showed that Andro enhances PTX therapeutic effect in the drug-resistant KBChR 8-5 cells.

Tetrazole and oxadiazole derivatives as bioisosteres of tariquidar and elacridar: New potent P-gp modulators acting as MDR reversers

New 2,5- and 1,5-disubstituted tetrazoles, and 2,5-disubstituted-1,3,4-oxadiazoles were synthesized as tariquidar and elacridar derivatives and studied as multidrug resistance (MDR) reversers. Their behaviour on the three ABC transporters P-gp, MRP1 and BCRP was investigated. All compounds inhibited the P-gp transport activity in MDCK-MDR1 cells overexpressing P-gp, showing EC50 values even in the low nanomolar range (compounds 15, 22). Oxadiazole derivatives were able to increase the antiproliferative effect of doxorubicin in MDCK-MDR1 and in HT29/DX cells confirming their nature of P-gp modulators, with derivative 15 being the most potent in these assays. Compound 15 also displayed a dual inhibitory effect showing good activities towards both P-gp and BCRP. A computational study suggested a common interaction pattern on P-gp for most of the potent compounds. The bioisosteric substitution of the amide group of lead compounds allowed identifying a new set of potent oxadiazole derivatives that modulate MDR through inhibition of the P-gp efflux activity. If compared to previous amide derivatives, the introduction of the heterocycle rings greatly enhances the activity on P-gp, introduces in two compounds a moderate inhibitory activity on MRP1 and maintains in some cases the effect on BCRP, leading to the unveiling of dual inhibitor 15.

Analysis of P-Glycoprotein Transport Cycle Reveals a New Way to Identify Efflux Inhibitors

P-glycoprotein (P-gp) is found to be of considerable interest for the design of drugs capable of treating chemoresistant tumors. This transporter is an interesting target for which an efficient approach has not yet been developed in terms of computer simulation. In this work, we use a combination of docking, molecular dynamics, and metadynamics to fully explore the states that occur during the capture of a ligand and subsequent efflux by P-gp. The proposed approach allowed us to substantiate a number of experimentally established facts, as well as to develop a new criterion for identifying potential P-gp inhibitors.