dihydropyridines and Precursor-Cell-Lymphoblastic-Leukemia-Lymphoma

The requirement of P-glycoprotein, a product of the multidrug resistance (MDR)1 gene, for natural killer (NK) cell-mediated cytotoxicity was examined by using a human NK-like cell line, YTN, which is cytotoxic toward JY cells. YTN cells express P-glycoprotein, a judged by flow cytometry and polymerase chain reaction of reverse-transcribed mRNA. YTN cell-mediated cytotoxicity was inhibited by MDR-reversing reagents as well as the F(ab')2 fragment of a monoclonal antibody against P-glycoprotein. Furthermore, antisense oligonucleotides for MDR1 mRNA inhibited expression of P-glycoprotein as well as YTN cell-mediated cytotoxicity. Thus, this study provides firm evidence that P-glycoprotein plays an essential role in cell-mediated cytotoxicity.

Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Cell Line; Cell Survival; Cytotoxicity, Immunologic; Dihydropyridines; Drug Resistance, Multiple; Humans; Killer Cells, Natural; Nicardipine; Oligonucleotides, Antisense; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Pyrazoles; RNA, Messenger; Thymoma; Thymus Neoplasms; Transcription, Genetic; Tumor Cells, Cultured

Cell membranes were prepared from the multidrug resistant, P-glycoprotein expressing human lymphoblastoid cell line CCRF-ADR 5000. The P-glycoprotein of these membranes possessed high affinity binding sites for [3H]vinblastine, with a Kd of 8 +/- 2 nM and Bmax of 17 +/- 8 pmol/mg of protein. The binding of [3H]vinblastine to P-glycoprotein was not ATP-dependent, and was inhibited by cytotoxic drugs with the following potency order; vincristine > doxorubicin > etoposide. The 1,4-dihydropyridine and multidrug resistance reversing agent, dexniguldipine-HCl, inhibited binding with a Ki value of 37 nM. The multidrug resistance reversing agent cyclosporin A, and the cytotoxics doxorubicin and etoposide did not alter the kinetics of [3H]vinblastine dissociation from P-glycoprotein; however, the 1,4-dihydropyridines dexniguldipine-HCl and nicardipine accelerated dissociation of [3H]vinblastine. These data suggest that P-glycoprotein possesses at least two allosterically coupled drug acceptor sites; receptor site 1 which binds vinblastine, doxorubucin, etoposide and cyclosporin A, and receptor site 2 which binds dexniguldipine-HCl and other 1,4-dihydropyridines.

Topics: Allosteric Regulation; ATP Binding Cassette Transporter, Subfamily B, Member 1; Binding, Competitive; Calcium Channel Blockers; Cell Division; Cyclosporine; Dihydropyridines; Doxorubicin; Drug Resistance, Multiple; Etoposide; Humans; Kinetics; Mathematics; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Tritium; Tumor Cells, Cultured; Vinblastine; Vincristine

Modulators for the reversal of multidrug resistance such as R-verapamil and B8509-035, a dihydropyridine, effectively overcome multidrug resistance in vitro and are currently undergoing clinical trial. One problem with their use is the application protocol; the question as to whether they should be given by continuous administration or in sequential doses in combination with the cytotoxic drugs has to be addressed. Therefore, we examined the influence of the exposure time and the sequence of modulator administration on the active transport of the fluorescent dye rhodamine 123 (R123), a substrate for the P-glycoprotein, in the resistant lymphoblastoid cell line VCR1000 and the parental nonresistant cell line CCRF-CEM. Our results demonstrate the importance of coadministration of R-verapamil and the cytotoxic agent for the modulation of multidrug resistance, whereas the exposure sequence does not seem to be such an essential parameter in the case of B8509-035. This observation should be considered for the further design of clinical studies.

Topics: Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cell Differentiation; Dihydropyridines; Dose-Response Relationship, Drug; Drug Interactions; Drug Resistance; Flow Cytometry; Humans; Membrane Glycoproteins; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Rhodamines; Tumor Cells, Cultured; Verapamil

We have examined the expression of P-glycoprotein (P-gp) in adult T-cell leukemia (ATL) samples from 25 patients. Based on immunoblotting with a monoclonal antibody against P-gp, C219, 8 of 20 ATL patients were P-gp positive at the initial presentation. All 6 patients at the relapsed stage were P-gp positive, and refractory to chemotherapy. The expression of MDR1 mRNA in P-gp-positive ATL cells was increased at the relapsed stage of one patient. P-gp of this patient was photolabeled with [3H]azidopine and the labeling was inhibited with nimodipine, vinblastine and progesterone. These results suggest that P-gp expressed in ATL cells from patients at relapsed stage has the same binding site(s) for the drugs as that in multidrug resistant cells, and is correlated with the refractory nature of the cells to chemotherapy.

Topics: Antibodies, Monoclonal; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Blast Crisis; Cell Line; Dihydropyridines; Gene Expression Regulation, Leukemic; Humans; Immunoblotting; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Leukemia, Myeloid, Acute; Leukemia, T-Cell; Lymph Nodes; Membrane Glycoproteins; Nimodipine; Polymerase Chain Reaction; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Progesterone; RNA, Messenger; Tritium; Vinblastine