The MDR1 (P-glycoprotein) and MRP (P-190) transporters do not play a major role in the intrinsic multiple drug resistance of Jurkat T lymphocytes.
The response of T cells in relation to the cell cycle has not been extensively studied. We have attempted to address this question using Jurkat T cells treated with cytostatic drugs known to arrest cells at various transition points of their cycle. We tested several concentrations of drugs that act at G1/S (hydroxyurea, lovastatin, thymidine), early S (aphidicolin, cyclosporin A, rapamycin) or G2+M (colchicine, nocodazole) in 24 h cultures. Cytofluorimetric analyses showed that cycling Jurkat cells were equally distributed between the G1 (44.9 +/- 6.5%) and S (42.3 +/- 8.0%) phases. Cell distribution in G2+M was 12.7 +/- 2.8%. Hydroxyurea but not lovastatin increased the percentage of cells in S phase to approximately 60-70% and both drugs decreased it to approximately 30% in G1. Thymidine had no effects. Aphidicolin increased the distribution in S phase to approximately 70% with a decrease in G1 to approximately 30%. Cyclosporin A and rapamycin increased the percentage of the cells in G1 to approximately 70% and decreased it to approximately 25% in S phase. Nocodazole increased cell distribution in G2+M to approximately 60% and induced a decrease in G1 to approximately 10%. The effects of the drugs were not related to their toxicity and their limited efficiency raised the possibility that Jurkat cells possessed an intrinsic resistance to these xenobiotics. Time-course analysis showed (scanning electron microscopy) that the early morphological changes induced by colchicine were reversible. Drug efflux experiments (vinblastine) suggested that an ATP-dependent process could be involved. However, Northern blot analyses showed a weak signal for MDR1 (P-glycoprotein). In contrast, a probe for MRP (P-190) showed a strong signal in Jurkat and peripheral lymphocytes. The presence of drugs (cyclosporin A, nocodazole, thymidine) (24 h) did not upregulate its message and cell treatment with DL-butathione (S,R)-sulfoximine only moderately affected the efficiency of the glutathione S-conjugate MRP transporter. Our data suggest that the intrinsic multidrug resistance of leukemic Jurkat T cells does not appear to involve the MDR1 and MRP members of the ABC family of reverse drug transporters and these observations raise the possibility of the involvement of multifaceted mechanisms.
Martel
J
J
Department of Biochemistry, Faculty of Medicine, University of Sherbrooke, Quebec, Canada.
Payet
M D
MD
Dupuis
G
G
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000493:pharmacokinetics / Q000494:pharmacology; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003078:Colchicine / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000502:physiology*; D005978:Glutathione / Q000096:biosynthesis; D006801:Humans; D019169:Jurkat Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012333:RNA, Messenger / Q000378:metabolism; D016196:S Phase / Q000187:drug effects; D015854:Up-Regulation; D014747:Vinblastine / Q000493:pharmacokinetics / Q000494:pharmacology
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D000964:Antimetabolites, Antineoplastic; D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; D019328:Buthionine Sulfoximine; D003078:Colchicine; D005978:Glutathione; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012333:RNA, Messenger; D014747:Vinblastine