thioinosine and Leukemia--Myeloid

The experience with myeloproliferative diseases (MPD) in children of a large pediatric hematology-oncology service during a 20-year period is reviewed. Twenty-seven patients with myeloproliferative diseases were treated, six with the juvenile type of chronic myelogenous leukemia (CML), 10 with the adult type of CML, three with familial MPD, one with unclassifiable MPD, and seven with acute leukemia in whom myelofibrosis was either a prodromal or terminal event. The literature is reviewed with particular emphasis regarding the relationships between the juvenile type of CML and monocytic leukemia, the adult type of CML and acute nonlymphocytic leukemia, and the relationship of myelofibrosis and myeloid metaplasia to the acute leukemias. New therapeutic approaches are needed in this heterogenous but interrelated group of disorders.

Topics: Adolescent; Adrenal Cortex Hormones; Busulfan; Cell Transformation, Neoplastic; Child; Child, Preschool; Chromosomes, Human, 21-22 and Y; Female; Fetal Hemoglobin; Humans; Infant; Leukemia, Erythroblastic, Acute; Leukemia, Myeloid; Male; Methotrexate; Myeloproliferative Disorders; Primary Myelofibrosis; Thioinosine

Despite advances in oncology drug development, most commonly used cancer therapeutics exhibit serious adverse effects. Often the toxicities of chemotherapeutics are due to the induction of significant DNA damage that is necessary for their ability to kill cancer cells. In some clinical situations, the direct induction of significant cytotoxicity is not a requirement to meet clinical goals. For example, differentiation, growth arrest, and/or senescence is a valuable outcome in some cases. In fact, in the case of acute myeloid leukemia (AML), the use of the differentiation agent all-trans-retinoic acid (ATRA) has revolutionized the therapy for a subset of leukemia patients and led to a dramatic survival improvement. Remarkably, this therapeutic approach is possible even in many elderly patients, who would not be able to tolerate therapy with traditional cytotoxic chemotherapy. Because of the success of ATRA, there is widespread interest in identifying differentiation strategies that may be effective for the 90-95% of AML patients who do not clinically respond to ATRA. Utilizing an AML differentiation agent that is in development, we found that AML differentiation can be induced through ATP depletion and the subsequent activation of DNA damage signaling through an ATR/Chk1-dependent and p53-independent pathway. This study not only reveals mechanisms of AML differentiation but also suggests that further investigation is warranted to investigate the potential clinical use of low dose chemotherapeutics to induce differentiation instead of cytotoxicity. This therapeutic approach may be of particular benefit to patients, such as elderly AML patients, who often cannot tolerate traditional AML chemotherapy.

Topics: Acute Disease; Adenosine; Adenosine Triphosphate; Antibiotics, Antineoplastic; Ataxia Telangiectasia Mutated Proteins; Blotting, Western; Caffeine; Cell Cycle Proteins; Cell Differentiation; Cell Line, Tumor; Cell Proliferation; Checkpoint Kinase 1; Comet Assay; DNA Damage; Doxorubicin; HEK293 Cells; Humans; Leukemia, Myeloid; Protein Kinase Inhibitors; Protein Kinases; Protein Serine-Threonine Kinases; Signal Transduction; Staurosporine; Thioinosine; Tumor Suppressor Protein p53

Cyclopentenyl cytosine (CPEC) is a carbocyclic cytidine analog inhibitor of CTP synthetase and experimental drug for combination chemotherapy. CPEC treatment (50 nM) depleted intracellular CTP and induced a specific S-phase arrest and erythroid differentiation of human erythroleukemia K562 cells. The equilibrative nucleoside transporters (ENT1, 2) facilitated uptake of CPEC into K562 cells as evidenced by both NBMPR and dipyridamole inhibition of CPEC-mediated CTP depletion and erythroid differentiation. Incubation with the pyridinylimidazole p38 MAPK inhibitors, SB203580 or SB220025, suppressed both the CPEC-induced cell cycle arrest and differentiation of K562 cells. SB203580 also prevented the cell cycle arrest and erythroid differentiation of K562 cells induced by Leflunomide (LEF), a non-nucleoside inhibitor of the de novo pyrimidine pathway, without affecting LEF-induced depletion of pyrimidine pools. Finally, selective knockdown of p38 MAPK by using Smart Pooltrade mark siRNA to p38 MAPK significantly decreased the CPEC-induced differentiation of K562 cells. These results suggest that endogenous activity of p38 MAP kinases may be required for committing K562 cells to cell cycle arrest and erythroid differentiation under conditions of CTP depletion.

Topics: Affinity Labels; Carbon-Nitrogen Ligases; Cell Differentiation; Cytidine; Cytidine Triphosphate; Dipyridamole; Enzyme Inhibitors; Equilibrative Nucleoside Transporter 1; Erythroid Precursor Cells; Humans; Isoxazoles; K562 Cells; Leflunomide; Leukemia, Myeloid; p38 Mitogen-Activated Protein Kinases; Phosphodiesterase Inhibitors; Pyrimidines; RNA, Small Interfering; S Phase; Thioinosine

Quantitation of equilibrative, nitrobenzylthioinosine (NBMPR) sensitive (es) nucleoside transporters on blast cells isolated from patients with acute myeloblastic leukemia is useful in predicting intracellular accumulation of the antileukemic nucleoside drug, cytosine arabinoside. We previously reported the synthesis of a fluorescein-labeled ligand for the es nucleoside transporter, 5-(SAENTA-x2)-fluorescein. This paper reports the synthesis of 5-(SAENTA-x8)-fluorescein in which the linkage between fluorescein and nucleoside ligand has been increased from 2 atoms to 8 atoms. This new ligand had a sixfold increase in affinity (Kd 0.9 +/- 0.1 nM) as well as an 86% increase in the cell associated fluorescence output compared to its prototype 5-(SAENTA-x2)-fluorescein. The fluorescence signal arising from 5-(SAENTA-x8)-fluorescein specifically bound to freshly isolated and cultured leukemic myeloblasts was converted to molecules of equivalent soluble fluorescein (MESF) using standardized fluorescein microbeads and compared with the number of es nucleoside transporter sites assayed concurrently by [3H]NBMPR equilibrium binding analysis. A high correlation between the two assays was observed (r = 0.98), which enabled the cell-bound fluorescence output of 5-(SAENTA-x8)-fluorescein to be expressed in numbers of es nucleoside transporter sites per cell. The improved properties of 5-(SAENTA-x8)-fluorescein over those of its prototype molecule make it a suitable reagent for flow cytometric quantitation of nucleoside transporter expression on leukemic cells isolated from patient samples.

Topics: Adenosine; Binding Sites; Carrier Proteins; Cell Line; Cytarabine; Fluoresceins; Humans; Leukemia, Myeloid; Ligands; Membrane Proteins; Nucleoside Transport Proteins; Purine Nucleosides; Thioinosine; Thionucleosides

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: Adult; Aged; Cell Transformation, Neoplastic; Female; Humans; Leukemia, Myeloid; Male; Middle Aged; Prednisolone; Thioinosine; Vincristine

Survival and response to chemotherapy were evaluated in 84 adults with granulocytic leukemia (AGL) and 22 with acute lymphocytic leukemia (ALL). Twenty-two of the 84 patients with AGL reveived no chemotherapy (untreated group). The median survival for patients with AGL who achieved complete remission (CR) was 17.1 months, compared to 6.5 months for those who achieved partial remission (PR (p less than 0.05), 2.8 months for those who failed chemotherapy (p less than 0.01), and 2.1 months for the untreated group (p less than 0.01). The median survival for patients with ALL who achieved a CR was 18.2 months, compared to 7.3 months for those who achieved a PR and 7.0 months for those who failed chemotherapy. Of patients with AGL who reveived an adequate trial of chemotherapy, 43% achieved a CR and 16% a PR; 75% of patients with ALL achieved a CR and 13% a PR. Improved survival depends on the induction of a complete or partial remission with the use of aggressive chemotherapy.

Topics: Acute Disease; Adolescent; Adult; Aged; Child; Cyclophosphamide; Daunorubicin; Drug Therapy, Combination; Humans; Leukemia, Lymphoid; Leukemia, Myeloid; Mercaptopurine; Methotrexate; Middle Aged; Prednisone; Thioguanine; Thioinosine; Vincristine