thioinosine and Leukemia--Erythroblastic--Acute

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

Equilibrative nucleoside transport processes in mammalian cells are categorized as either nitrobenzylthioinosine (NBMPR)-sensitive (es) or NBMPR-insensitive (ei). Inhibition of the es process arises from binding of NBMPR to a high-affinity site(s) on the es transporter that can be identified by photoaffinity labeling with [3H]NBMPR. This study examined the equilibrative nucleoside transport processes of cultured human erythroleukemia (K562) cells. The presence of NBMPR binding sites (4.8 +/- 0.9 x 10(5)/cell, Kd = 0.3 nM), together with the identification of polypeptides by specific photolabeling of membranes with [3H]NBMPR, indicated that K562 cells possess es nucleoside transporters (ca 500,000 copies/cell). The photolabeled polypeptides of K562 cells migrated with lower relative mobility (peak M(r) value, 63,000) than did those of human erythrocytes (peak M(r) value, 53,000). This difference in apparent M(r) was abolished by prolonged treatment of membrane proteins with N-glycosidase F, suggesting that equilibrative nucleoside transport in K562 cells and erythrocytes is mediated by the same, or a closely related, es isoform. A cDNA encoding the es nucleoside transporter of human placenta (termed hENT1) was recently isolated by a strategy based on the N-terminal sequence of the es transporter of human erythrocytes. hENT-like mRNA species were detected in K562 cells, as well as in several other human cell lines of neoplastic origin (A459, G361, HeLa, HL-60, Molt-4, Raji, SW480), by high-stringency northern analysis with a placental hENT1 probe. A cDNA that encoded a protein identical to hENT1 was isolated by reverse transcriptase polymerase chain reaction with primers specific for hENT1. NBMPR inhibited zero-trans influx of 3H-labeled adenosine, uridine and thymidine by 50% (IC50 values) at 0.4-1.0 nM, confirming the presence of an NBMPR-sensitive (es) transport process, which accounted for 80-90% of total transport activity. The remaining component was identified as the equilibrative NBMPR-insensitive (ei) transport process since it: (i) exhibited low (IC50 > 1.0 microM) sensitivity to NBMPR; (ii) was not concentrative; and (iii) was unchanged by elimination of the sodium gradient. The kinetic parameters (determined at 37 degrees C) for the es- and ei-mediated processes differed markedly. Values for transport of uridine by the es- and ei-mediated processes were, respectively: K(m) = 229 +/- 39 and 1077 +/- 220 microM; Vmax, 186 +/- 31 and 40 +/- 5 pmol/

Topics: Adenosine; Affinity Labels; Binding Sites; Blotting, Northern; Carrier Proteins; Cell Division; Cell Line; DNA, Complementary; Electrophoresis, Polyacrylamide Gel; Erythrocytes; Gene Amplification; Humans; In Vitro Techniques; Leukemia, Erythroblastic, Acute; Membrane Proteins; Nucleoside Transport Proteins; Polymerase Chain Reaction; Protein Binding; Thioinosine; Thymidine; Tubercidin; Uridine

The results above show that mammalian cells, as exemplified by MELC, can be selected to be resistant to Adox, and that the resistant cells have greatly decreased nucleoside transport capacity. Since no mutagen was used prior to the selection process and Adox resistance was genetically stable, it appears that within a population of normal cells there is a genetically controlled range of expression of the nucleoside transporter. On the basis of the present data we cannot determine if the low level of nucleoside transporter in AR MELC is due to an altered form of the protein or a decreased amount of the normal protein. However the similarity of the Kd for NBTI in normal and AR MELC suggests that the latter is the case. Considerable indirect evidence is presented that Adox, with its ribose converted to an acyclic dialdehyde, is a substrate for the nucleoside transporter, adding a new type of compound to this list.

Topics: Adenosine; Animals; Carrier Proteins; Cell Division; Drug Resistance; Kinetics; Leukemia, Erythroblastic, Acute; Leukemia, Experimental; Membrane Proteins; Mice; Nucleoside Transport Proteins; S-Adenosylhomocysteine; Thioinosine; Tumor Cells, Cultured

Several antimetabolites have been demonstrated to have the capacity to initiate differentiation in vitro of a variety of leukemic cell lines. To explore the structural requirements for this activity, a series of purine and 8-substituted purine arabinofuranosyl and ribofuranosyl nucleoside derivatives were synthesized and tested as inducers of the differentiation of Friend murine erythroleukemia cells. 9-(beta-D-Arabinofuranosyl)hypoxanthine and 6-(hydroxyamino)-9-(beta-D-arabinofuranosyl)purine were effective inducers of maturation, producing 82% and 74% benzidine-positive cells, a measure of the number of cells synthesizing hemoglobin. 6-Mercapto-9-(beta-D-ribofuranosyl)purine and 6-(methylmercapto)-9-(beta-D-ribofuranosyl)purine and their corresponding beta-D-arabinofuranosyl derivatives were also effective initiators of maturation, causing approximately 50% of the cell population to assume a differentiated phenotype.

Topics: Animals; Antimetabolites; Arabinonucleosides; Cell Differentiation; Cell Division; Cell Line; Chemical Phenomena; Chemistry; Friend murine leukemia virus; Hematopoiesis; Leukemia, Erythroblastic, Acute; Mice; Purine Nucleosides; Ribonucleosides; Structure-Activity Relationship