piperidines and azidopine

Using three different cell lines exhibiting the MDR phenotype, we have studied the ability of eight different modulators to restore doxorubicin intracellular accumulation and to inhibit azidopine binding to membrane extracts. One cell line was of human origin (KB VI) and two of murine origin, overexpressing two different isoforms of the mdrl gene (C6 IV and C6 0.5). The modulators were distributed in different drug classes: cyclosporine A and PSC-833, quinine and quinidine, nifedipine and nicardipine, and verapamil and S-9788. We observed that there was no strict parallelism between restoration of doxorubicin intracellular accumulation and inhibition of azidopine binding. However, when considering separately each group of drugs, it appeared that the most potent drug in inhibiting azidopine labelling of P-glycoprotein (P-gp) was also the most potent in restoring doxorubicin accumulation. This indicates that azidopine binding cannot be used as a general screening test for the identification of new modulators, but rather at the level of the selection of potent analogues within a chemical family. The three cell lines behaved similarly, indicating that the structural diversity of P-pgs did not influence the efficiency and binding of modulators.

Topics: Affinity Labels; Animals; Antibiotics, Antineoplastic; Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Cyclosporine; Cyclosporins; Dihydropyridines; Doxorubicin; Drug Resistance, Multiple; Humans; Mice; Nicardipine; Piperidines; Triazines; Tumor Cells, Cultured; Verapamil

A new triazinoaminopiperidine derivative, Servier 9788 (S9788), was investigated for its ability to increase Adriamycin (ADR) accumulation and retention in two rodent (P388/ADR and DC-3F/AD) and three human (KB-A1, K562/R and COLO 320DM) cell lines displaying the P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) phenotype. Depending on the cell line S9788 was shown to be two to five times more active and five to 15 times more potent than Verapamil (VRP) in increasing ADR accumulation in resistant cells. ADR retention in KB-A1 cells maintained in a concentration of 10 microM S9788 was twice that in VRP-treated cells, and similar to that measured in the untreated sensitive KB-3-1 cells. Although 5 microM S9788 and 50 microM VRP gave the same values of ADR uptake in KB-A1 cells, S9788 was shown to induce a greater ADR retention following cell wash and post-incubation in resistance modifier- and ADR-free medium. Taking into account that S9788 had no effects on ADR accumulation and retention in sensitive KB-3-1 cells, it can be suggested that S9788 inhibits specifically the P-gp dependent ADR efflux, and in a manner less reversible than that observed with VRP. Moreover, [3H]azidopine photolabeling of P-gp, in P388/ADR plasma membranes, was completely inhibited by 100 microM S9788. Although S9788, as VRP, had no effect on the cell cycle of P388 cells, 5 microM S9788 increased 700-fold the efficacy of ADR to block P388/ADR cells in the G2+M phase of the cell cycle. Together, these results show that the sensitization, by S9788, of cell lines resistant to ADR is mainly due to an increase in ADR accumulation and retention, leading to an increase in the number of resistant cells blocked in the G2+M phase.

Topics: Adenocarcinoma; Animals; Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Carcinoma, Squamous Cell; Cell Cycle; Cell Membrane; Cells, Cultured; Colonic Neoplasms; Cricetinae; Cricetulus; Dihydropyridines; Doxorubicin; Drug Resistance; Flow Cytometry; Fluorescence; Humans; Kinetics; Leukemia P388; Leukemia, Myeloid, Acute; Lung; Membrane Glycoproteins; Mice; Piperidines; Sensitivity and Specificity; Triazines; Tritium; Tumor Cells, Cultured; Verapamil