thioinosine and Leukemia

Chemotherapy remains the major treatment modality in childhood acute nonlymphocytic leukemia (ANLL). Current remission induction rates range from 60% to 80%; but even with the improved rate of response to therapy, the median duration of remission has seldom exceeded 1 year. On the other hand, an increasing number of children with ANLL who were treated with intensive induction and maintenance chemotherapy regimens for a prescribed period followed by discontinuation of therapy are remaining in remission. The evolution of present-day chemotherapy approaches to childhood ANLL are reviewed in this article.

Topics: Acute Disease; Adolescent; Adult; Asparaginase; Azauridine; Child; Child, Preschool; Cyclophosphamide; Cytarabine; Daunorubicin; Drug Therapy, Combination; Humans; Leukemia; Prednisone; Thioguanine; Thioinosine; Vincristine

Topics: Animals; Breast Neoplasms; Chromatography, High Pressure Liquid; Chromatography, Ion Exchange; Deficiency Diseases; Female; Fluorouracil; Guanine; Humans; Inosine Monophosphate; Lesch-Nyhan Syndrome; Leukemia; Nucleosides; Nucleotides; Sarcoma 180; Skin; Thioinosine

The main roles of equilibrative nucleoside transporters (ENTs) and concentrative nucleoside transporters (CNTs) are to transfer single nucleosides and analogues for the nucleic acid salvage pathway. Oligodeoxyribonucleotides (ODNs) can be transported into the cytoplasm or nucleus of cells under certain conditions. Among ODNs composed of a single type of nucleotide, the transport efficiency differs with the length and nucleotide composition of the ODNs and varies in different types of leukaemia cells; among the 5 tested random sequence ODNs and 3 aptamers with varying sequences, the data showed that some sequences were associated with significantly higher transport efficiency than others. The transport of ODNs was sodium, energy, and pH-independent, membrane protein-dependent, substrate nonspecific for ODNs and 4-nitrobenzylthioinosine (NBMPR)-insensitive, but it showed a low sensitivity to dipyridamole (IC50 = 35.44 µmol/L), distinguishing it from ENT1-4 and CNTs. The delivery efficiency of ODNs was superior to that of Lipofection and Nucleofection, demonstrating its potential applications in research or therapeutics. Moreover, this process was associated with p38 mitogen activated protein kinase (p38MAPK) instead of c-Jun N-terminal kinase (JNK) signalling pathways. We have denoted ODN transmembrane transport as equilibrative nucleic acid transport (ENAT). Overall, these findings indicate a new approach and mechanism for transmembrane transport of ODNs.

Topics: Adolescent; Adult; Aged; Biological Transport; Child; Child, Preschool; Cytoplasm; Dipyridamole; Female; Humans; Infant; K562 Cells; Leukemia; Male; Middle Aged; Oligodeoxyribonucleotides; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Thioinosine

The mechanisms behind cellular anthracycline uptake are not completely understood. Knowledge about uptake mechanisms could be used to increase the selectivity of the drugs. We compared the uptake patterns of, daunorubicin (DNR), doxorubicin (DOX), epirubicin (EPI), idarubicin (IDA), and pirarubicin (PIRA) by cultured leukemic cells and investigated possible involvement of specific carriers.. HL-60 cells were incubated with anthracyclines for 1 hour in the absence or presence of transport inhibitors, suramin, or nucleosides and cellular drug uptake was determined. Cell survival was also determined. MCF-7 breast cancer cells were used as a negative control for concentrative nucleoside transporters (CNTs). Anthracycline concentration was determined with HPLC and fluorometric detection and apoptosis was determined with propidium iodide and flow cytometry.. DNR, IDA, and PIRA had higher uptake than DOX and EPI with a prominent increase in uptake at concentrations > 1 µM. Uptake of all anthracyclines was greatly reduced at 0°C. Suramin, a purinergic-2-receptor inhibitor, strongly inhibited the uptake of all anthracyclines except PIRA and increased cell survival. Dipyridamole, an equilibrative NT (ENT) inhibitor, significantly inhibited the uptake of DNR only. The addition of nucleosides significantly inhibited the uptake of DNR, IDA, and PIRA but not in MCF-7 cells lacking functional CNTs.. Our results suggest different uptake mechanisms for the anthracyclines studied. We found evidence for carrier mediated uptake mechanisms, supporting involvement of NTs in transmembrane transport of DNR, IDA, and PIRA. The results also showed a strong inhibition of suramin on anthracycline uptake by so far unknown mechanisms.

Topics: Anthracyclines; Antibiotics, Antineoplastic; Apoptosis; ATP Binding Cassette Transporter, Subfamily B, Member 1; Biological Transport; Dipyridamole; HL-60 Cells; Humans; Leukemia; MCF-7 Cells; Nucleoside Transport Proteins; Nucleosides; Purinergic Antagonists; Suramin; Temperature; Thioinosine; Verapamil

Cytosine arabinoside (1-beta-D-arabinofuranosylcytosine;Ara-C) is the most important antimetabolite used for acute leukemia. We established Ara-C (0.003-1 micromol/l)-resistant NALM-6 leukemia cells, and attempted the characterization of their resistance.. The Ara-C-resistant cell lines were developed by stepwise increases in the drug. The mRNA expressions were analyzed by reverse transcription-polymerase chain reaction (RT-PCR). The uptake of Ara-C, deoxycytidine kinase (dCK) activity and cytidine deaminase (CDA) activity were measured using radioisotope methods. Cytotoxicity was evaluated using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay.. The mRNA expression of human equilibrative nucleoside transporter-1 (hENT-1), which is an uptake transporter of Ara-C, was initially decreased during the acquisition of resistance to Ara-C. The expression of dCK, an activation enzyme, and of CDA, an inactivation enzyme, was decreased and increased in the late phase, respectively. The cytotoxic effect of Ara-C on parental NALM-6 cells was ameliorated by hENT-1 inhibitors. There were no differences in the cytotoxic effect of other anticancer drugs, but there was similar resistance to nucleoside analogues via hENT-1 between the parental and resistant cells.. Decreased hENT-1 expression and function is causatively responsible for the acquisition of Ara-C resistance and alterations in dCK and CDA contribute to the higher concentration range.

Topics: Cell Line, Tumor; Cell Survival; Cytarabine; Cytidine Deaminase; Cytoprotection; Deoxycytidine Kinase; Dipyridamole; Drug Resistance, Neoplasm; Gene Expression; Humans; Leukemia; RNA, Messenger; Thioinosine

The dose-response curves for the inhibition of equilibrative uridine transport by dilazep, dipyridamole and nitrobenzylthioinosine (NBMPR) in undifferentiated HL-60 cells were biphasic. Some 70% of the transport activity was inhibited with IC50 values of 0.7, 1 and 7 nM respectively. No inhibition of the remaining 30% of transport activity was observed until the dilazep, dipyridamole and NBMPR concentrations exceeded 1, 0.1 and 3 microM respectively. Exposure to phorbol 12-myristate 13-acetate (PMA) for 48 h, to induce monocytic differentiation, caused a 20-fold decrease in Vmax. of both NBMPR-sensitive and NBMPR-insensitive equilibrative uridine transport. The decrease in NBMPR-sensitive uridine transport induced by PMA corresponded to a decrease in NBMPR binding sites. A 30% decrease in specific NBMPR binding sites occurred within 6 h of PMA exposure, and could be prevented by uridine and thymidine at concentrations as low as 100 microM, and by staurosporine at 40 nM. However, the protective effects of these compounds diminished with prolonged PMA exposure. No protection was observed with uracil. Exogenous protein kinase C (PKC) in the presence of ATP and PMA decreased the number of specific NBMPR-binding sites in purified HL-60 cell plasma membranes. These results suggest that a PKC-induced conformational change in substrate-binding/transporting site may be responsible for the decrease in NBMPR-sensitive nucleoside transport during PMA-induced monocytic differentiation of HL-60 cells.

Topics: Affinity Labels; Alkaloids; Binding Sites; Biological Transport; Cell Differentiation; Dilazep; Dipyridamole; Humans; Kinetics; Leukemia; Monocytes; Protein Kinase C; Staurosporine; Tetradecanoylphorbol Acetate; Thioinosine; Thymidine; Tumor Cells, Cultured; Uracil; Uridine

Topics: Biological Transport; Carrier Proteins; Humans; Leukemia; Lymphocytes; Lymphoma; Membrane Proteins; Nucleoside Transport Proteins; Pentostatin; Thioinosine; Tumor Cells, Cultured

Accumulation of cytosine arabinoside triphosphate (araCTP) from a range of cytosine arabinoside (araC) concentrations (1-50 microM) was measured during incubations of leukemic cells freshly isolated from patients with acute leukemia. In all but one patient, increments in extracellular araC above 10 microM did not increase intracellular araCTP levels. This maximal level of araCTP accumulation ranged from 254 to 1607 pmol/10(7) cells attained after 1 h incubation and did not correlate with either the number of nucleoside transporters on the cell membrane or the Vmax of araC phosphorylation in cell free extracts. Extremely low araCTP accumulation (103 pmol/10(7) cells/h at 50 microM araC) was observed in an AML patient with the unusual finding of micromyeloblasts. These cells also had very low numbers of nucleoside transport sites (less than 500 sites/cell) and were mitotically inactive. The unique feature of the myeloblasts from this patient was that intracellular araCTP accumulation showed a linear dependence on extracellular araC up to 50 microM with no evidence of saturation.

Topics: Acute Disease; Arabinofuranosylcytosine Triphosphate; Arabinonucleotides; Binding Sites; Biological Transport; Cell Membrane; Cytarabine; Deoxycytidine Kinase; Extracellular Space; Humans; Leukemia; Lymphocytes; Nucleosides; Phosphorylation; Thioinosine; Tumor Cells, Cultured

The interactions of the epipodophyllotoxins, teniposide (VM-26) and etoposide (VP-16), with the nucleoside carrier were examined with emphasis on their effects on 1-beta-D-arabinofuranosylcytosine (ara-C) transport and net accumulation. VM-26 inhibited ara-C transport by Ehrlich ascites cells within 1 min of exposure, and inhibition was only partially reversed after 45 min in VM-26-free medium. ara-C transport was slowed by 50% by 7 microM VM-26 or by 35 microM VP-16. Since epipodophyllotoxins were noncompetitive inhibitors, fractional inhibition was independent of the ara-C concentration. Analysis of ara-C transport kinetics revealed only a single saturable transport route, and there was no indication of VM-26-insensitive transport. VM-26, VP-16, and ara-C were competitive inhibitors of the specific binding of nitrobenzylthioinosine to the nucleoside carrier with Ki values of 7.4 microM, 23 microM, and 2.2 microM, respectively. The rate of dissociation of nitrobenzylthioinosine (t 1/2 = 20.6 min) was accelerated by 5 microM ara-C (t 1/2 = 18.5 min) but slowed by 100 microM VM-26 (t 1/2 = 34.6). By these criteria, the interaction of VM-26 with the nucleoside carrier was qualitatively similar to that of dipyridamole. Although VM-26 inhibited ara-C transport, it did not significantly slow the rate of net intracellular accumulation of ara-C by Ehrlich cells, presumably because transport capacity far exceeds the capacity for phosphorylation in these cells. In freshly isolated human leukemic blasts, which have far less nucleoside transport activity, inhibition of ara-C accumulation by VM-26 was dependent on the ara-C concentration. At 1 microM ara-C, a concentration where transport was rate limiting for net uptake, VM-26 inhibited accumulation of ara-C over a 60-min time course. At 50 microM ara-C, transport was in excess, and VM-26 did not slow ara-C metabolism.

Topics: Animals; Binding Sites; Biological Transport; Carcinoma, Ehrlich Tumor; Cells, Cultured; Cytarabine; Etoposide; Humans; Leukemia; Male; Mice; Mice, Inbred Strains; Podophyllotoxin; Teniposide; Thioinosine; Tritium

The membrane transport of cytosine arabinoside (araC) has been studied in blasts freshly isolated from a variety of acute leukaemias. The major fraction of araC influx was facilitated and this fraction was 80-87% at l microM araC and 68-80% at 200 microM araC. Competitive kinetics were observed between araC and deoxycytidine for entry into leukaemic blasts and, moreover, araC influx was blocked by phloretin, a broad-spectrum inhibitor of facilitated transport systems. Kinetic analysis of facilitated araC influx gave KmS which varied over a 10-fold range between patients and which were positively correlated to the Vmax. Nucleoside influx Vmax also varied over an 80-fold range between individuals, although the mean araC transport was 4-fold greater in myeloblasts than in lymphoblasts. Larger transport of araC may explain the greater sensitivity of acute myeloid leukaemia to this drug.

Topics: Acute Disease; Adolescent; Adult; Aged; Biological Transport; Cell Membrane; Child; Child, Preschool; Cytarabine; Deoxycytidine; Humans; Infant; Kinetics; Leukemia; Leukocytes; Middle Aged; Phloretin; Thioinosine

Although cytosine arabinoside (araC) can induce a remission in a majority of patients presenting with acute myeloblastic leukemia (AML), a minority fail to respond and moreover the drug has less effect in acute lymphoblastic leukemia (ALL). The carrier-mediated influx of araC into purified blasts from patients with AML, ALL, and acute undifferentiated leukemia (AUL) has been compared to that of normal lymphocytes and polymorphs. Blasts showed a larger mediated influx of araC than mature cells, since mean influxes for myeloblasts and lymphoblasts were 6- and 2.3-fold greater than polymorphs and lymphocytes, respectively. Also, the mean influx for myeloblasts was fourfold greater than the mean for lymphoblasts. The number of nucleoside transport sites was estimated for each cell type by measuring the equilibrium binding of [(3)H]nitrobenzylthioinosine (NBMPR), which inhibits nucleoside fluxes by binding with high affinity to specific sites on the transport mechanism. The mean binding site numbers for myeloblasts and lymphoblasts were 5- and 2.8-fold greater, respectively, than for the mature cells of the same maturation series. The mean number of NBMPR binding sites for myeloblasts was fourfold greater than for lymphoblasts. Patients with AUL were heterogeneous since blasts from some gave values within the myeloblastic range and others within the lymphoblastic range. The araC influx correlated closely with the number of NBMPR binding sites measured in the same cells on the same day. Transport parameters were measured on blasts from 15 patients with AML or AUL who were then treated with standard induction therapy containing araC. Eight patients entered complete remission, while seven failed therapy, among whom were the three patients with the lowest araC influx (<0.4 pmol/10(7) cells per min) and NBMPR binding (<3,000 sites/cell) for the treated group. In summary, myeloblasts have both higher araC transport rates and more nucleoside transport sites than lymphoblasts and this factor may contribute to the greater sensitivity of AML to this drug. AraC transport varied >10-fold between leukemic blasts and normal leukocytes, but transport capacity related directly to the number of nucleoside transport sites on the cell. Finally, low araC transport rates or few NBMPR binding sites on blasts were observed in a subset of patients with acute leukemia who failed to achieve remission with drug combinations containing araC.

Topics: Acute Disease; Adolescent; Adult; Aged; Binding Sites; Bone Marrow Cells; Carrier Proteins; Cell Transformation, Neoplastic; Child; Child, Preschool; Cytarabine; Humans; Infant; Leukemia; Leukemia, Myeloid; Leukemia, Myeloid, Acute; Leukocytes; Middle Aged; Nucleosides; Thioinosine; Time Factors

Topics: Acute Disease; Bacterial Infections; Child; Child, Preschool; Humans; Leukemia; Leukemia, Lymphoid; Methotrexate; Prednisolone; Thioinosine; Vincristine

Topics: Acute Disease; Cell Transformation, Neoplastic; Cytarabine; Daunorubicin; Humans; Leukemia; Prednisolone; Thioinosine

Topics: Acute Disease; Adolescent; Adult; Cytarabine; Daunorubicin; Female; Humans; Leukemia; Male; Middle Aged; Prednisolone; Thioinosine

Topics: Acute Disease; Adolescent; Adult; Aged; Antineoplastic Agents; Cytarabine; Daunorubicin; Drug Therapy, Combination; Humans; Leukemia; Middle Aged; Prednisolone; Thioguanine; Thioinosine

Leukocytes from patients with leukemia and L1210 cells from mice were examined for the rate of formation and cellular concentration of phosphoribosylpyrophosphate, the rate of thioinosinic acid formation, and a number of selected enzymes involved in purine nucleotide synthesis. The amount of thioinosinic acid formed in L1210 cells was much higher than that in human leukemic leukocytes. In cell extracts, the synthesis of thioinosinic acid was similar in both cell types, and the amount of purine phosphoribosyltransferase was not rate limiting in either case. Much higher concentrations and rates of formation of phosphoribosylpyrophosphate were found in L1210 cells than in human leukemic leukocytes. The difference in response to 6-mercaptopurine between L1210 cells and human leukemic leukocytes might be attributed to their difference in supply of phosphoribosylpyrophosphate. Phosphoribosylpyrophosphate-amidotransferase was found to be high in L1210 cells, but was not detected in human leukemic leukocytes.

Topics: Animals; Erythrocytes; Humans; In Vitro Techniques; Leukemia; Leukemia L1210; Leukocytes; Mercaptopurine; Mice; Phosphoribosyl Pyrophosphate; Thioinosine

Topics: Antineoplastic Agents; Bone Marrow Examination; Erythrocyte Count; Hemorrhage; Humans; Leukemia; Leukocyte Count; Leukopenia; Mercaptopurine; Nucleosides; Thioinosine; Toxicology

Topics: Antimetabolites; Child; Humans; Infant; Leukemia; Mercaptopurine; Thioinosine

Topics: Antimetabolites; Child; Humans; Infant; Leukemia; Mercaptopurine; Purines; Thioinosine