tretinoin and Preleukemia

Topics: Anemia, Aplastic; Antineoplastic Agents; Blood Transfusion; Bone Marrow; Bone Marrow Transplantation; Cell Differentiation; Colony-Stimulating Factors; Humans; Myelodysplastic Syndromes; Preleukemia; Prognosis; Tretinoin

The myelodysplastic syndromes represent a preleukaemic state in which a clonal abnormality of haemopoietic stem cell is characterised by a variety of phenotypic manifestations with varying degrees of ineffective haemopoiesis. This state probably develops as a sequence of events in which the earliest stages may be difficult to detect by conventional pathological techniques. The process is characterised by genetic changes leading to abnormal control of cell proliferation and differentiation. Expansion of an abnormal clone may be related to independence from normal growth factors, insensitivity to normal inhibitory factors, suppression of normal clonal growth, or changes in the immunological or nutritional condition of the host. The haematological picture is of peripheral blood cytopenias: a cellular bone marrow, and functional abnormalities of erythroid, myeloid, and megakaryocytic cells. In most cases marrow cells have an abnormal DNA content, often with disturbances of the cell cycle: an abnormal karyotype is common in premalignant clones. Growth abnormalities of erythroid or granulocyte-macrophage progenitors are common in marrow cultures, and lineage specific surface membrane markers indicate aberrations of differentiation. Progression of the disorder may occur through clonal expansion or through clonal evolution with a greater degree of malignancy. Current attempts to influence abnormal growth and differentiation have had only limited success. Clinical recognition of the syndrome depends on an acute awareness of the signs combined with the identification of clonal and functional abnormalities.

Topics: Anemia, Refractory, with Excess of Blasts; Animals; Antineoplastic Agents; Blood Cell Count; Bone Marrow; Cell Transformation, Neoplastic; Cholecalciferol; Chromosome Aberrations; Chromosome Disorders; Colony-Forming Units Assay; Colony-Stimulating Factors; DNA; Hematopoietic Stem Cells; Humans; Leukemia; Leukemia, Radiation-Induced; Mice; Myelodysplastic Syndromes; Oncogenes; Preleukemia; Rats; Tretinoin

The origin of aberrant DNA methylation in cancer remains largely unknown. In the present study, we elucidated the DNA methylome in primary acute promyelocytic leukemia (APL) and the role of promyelocytic leukemia-retinoic acid receptor α (PML-RARα) in establishing these patterns. Cells from APL patients showed increased genome-wide DNA methylation with higher variability than healthy CD34(+) cells, promyelocytes, and remission BM cells. A core set of differentially methylated regions in APL was identified. Age at diagnosis, Sanz score, and Flt3-mutation status characterized methylation subtypes. Transcription factor-binding sites (eg, the c-myc-binding sites) were associated with low methylation. However, SUZ12- and REST-binding sites identified in embryonic stem cells were preferentially DNA hypermethylated in APL cells. Unexpectedly, PML-RARα-binding sites were also protected from aberrant DNA methylation in APL cells. Consistent with this, myeloid cells from preleukemic PML-RARα knock-in mice did not show altered DNA methylation and the expression of PML-RARα in hematopoietic progenitor cells prevented differentiation without affecting DNA methylation. Treatment of APL blasts with all-trans retinoic acid also did not result in immediate DNA methylation changes. The results of the present study suggest that aberrant DNA methylation is associated with leukemia phenotype but is not required for PML-RARα-mediated initiation of leukemogenesis.

Topics: Animals; Cell Transformation, Neoplastic; Chromosomes, Human; CpG Islands; Disease Progression; DNA Methylation; DNA, Neoplasm; Gene Expression Regulation, Leukemic; Gene Knock-In Techniques; Hematopoietic Stem Cells; Humans; Leukemia, Promyelocytic, Acute; Mice; Mice, Inbred C57BL; Neoplasm Proteins; Neoplastic Stem Cells; Oncogene Proteins, Fusion; Phenotype; Polycomb Repressive Complex 2; Preleukemia; Recombinant Fusion Proteins; Repressor Proteins; Transcription Factors; Tretinoin

Acute promyelocytic leukemia (APL) is characterized by hyperproliferation of promyelocytes, progenitors that are committed to terminal differentiation into granulocytes, making it an ideal disease in which to study the transforming potential of less primitive cell types. We utilized a murine model of APL in which the PML-RARalpha oncogene is expressed from the endogenous cathepsin G promoter to test the hypothesis that leukemia stem cell (LSC) activity resides within the differentiated promyelocyte compartment. We prospectively purified promyelocytes from transgenic mice at various stages of disease and observed that PML-RARalpha-expressing promyelocytes from young preleukemic mice had acquired properties of self-renewal both in vitro and in vivo. Progression to acute leukemia was associated with an expansion of the promyelocyte compartment at the expense of other stem, progenitor and terminally differentiated populations. Leukemic promyelocytes exhibited properties of self-renewal, and were capable of engendering leukemia in secondary recipient mice. These data indicate that PML-RARalpha alone can confer properties of self-renewal to committed hematopoietic progenitors before the onset of disease. These findings are consistent with the hypothesis that cancer stem cells may arise from committed progenitors that lack stem cell properties, provided that the initiating mutation in cancer progression activates programs that confer properties of self-renewal.

Topics: Animals; Antineoplastic Agents; Bone Marrow Transplantation; Cathepsin G; Cathepsins; Cell Division; Granulocyte Precursor Cells; Granulocytes; Hematopoietic Stem Cells; Humans; Leukemia, Promyelocytic, Acute; Mice; Mice, Inbred C57BL; Neoplastic Stem Cells; Oncogene Proteins, Fusion; Preleukemia; Promoter Regions, Genetic; Radiation Chimera; Recombinant Fusion Proteins; Serine Endopeptidases; Transgenes; Tretinoin

Topics: Antineoplastic Combined Chemotherapy Protocols; Biomarkers, Tumor; Chromosomes, Human, Pair 15; Chromosomes, Human, Pair 17; Cytarabine; Daunorubicin; Disease Progression; Etoposide; Female; Humans; Idarubicin; Karyotyping; Leukemia, Promyelocytic, Acute; Male; Middle Aged; Neoplasm Proteins; Oncogene Proteins, Fusion; Polycythemia Vera; Preleukemia; Prognosis; Remission Induction; Thrombocythemia, Essential; Thrombophilia; Translocation, Genetic; Tretinoin

Numerous agents induce differentiation and maturation of neoplastic and dysplastic myeloid cells in vitro and some of these agents have been used with limited success in the treatment of patients with myelodysplastic syndromes (MDS) and myeloid leukaemias. We recently proposed that physiological and pharmacological agents which enhance differentiation and maturation in vitro act by two fundamentally different routes: (1) by hastening the progression through various differentiation/maturation steps; (2) by slowing proliferation (usually by inhibition of DNA synthesis). In order to test this thesis we looked for synergistic effects on differentiation using pairs of agents from the two groups in cultures of cells from myelodysplastic and acute myeloid leukaemia (AML) patients and from normal marrow donors. The results with three MDS, two AML and three normal samples show that combinations of differentiation inducing agents (retinoic acid, N-methylformamide) with DNA synthesis inhibitors (6-mercaptopurine, cytosine arabinoside and aphidicolin) produce a differentiation inducing effect equivalent to that of 10-100, or even 1000 fold higher concentrations of single agents. Myelotoxic effects in vitro were not synergistic. The use of these synergistic combinations should greatly enhance the usefulness of differentiation inducers in the therapy of MDS and myeloid leukaemia.

Topics: Antineoplastic Combined Chemotherapy Protocols; Aphidicolin; Bone Marrow; Bone Marrow Diseases; Cell Differentiation; Cells, Cultured; Cytarabine; Diterpenes; DNA; Drug Synergism; Formamides; Humans; Leukemia, Myeloid, Acute; Mercaptopurine; Preleukemia; Syndrome; Tretinoin

13-cis-Retinoic acid (13-cRA) induces maturation and differentiation of neoplastic myeloid cell lines in vitro. We conducted a phase I clinical trial of 13-cRA in patients with myelodysplastic syndromes (MDS), using a single daily oral dose schedule. Seventeen patients with MDS and one each with acute nonlymphoblastic leukemia and chronic myelogenous leukemia in blast crisis were treated with 13-cRA at doses ranging from 20 to 125 mg/m2/day. Hepatotoxicity was dose-limiting and was manifested by hyperbilirubinemia and increased SGOT levels. This effect was seen only at the highest dose level of 125 mg/m2/day and was completely reversible upon cessation of the drug. Other toxic effects were mild, and included cheilosis, hyperkeratosis, stomatitis, and elevation of serum triglyceride levels. Fifteen patients with MDS were evaluable for therapeutic response. Five patients showed improvement in hematologic parameters. These responses included normalization of bone marrow blast count and increases in leukocyte count, platelet count, and/or hemoglobin concentration. Responses were generally not seen until at least 3 weeks of therapy were completed. We conclude that further study of 13-cRA in myelodysplastic syndromes is warranted and recommend that future studies utilize a starting dose of 100 mg/m2.

Topics: Administration, Oral; Adult; Aged; Blood Cell Count; Dose-Response Relationship, Drug; Drug Evaluation; Female; Humans; Isotretinoin; Leukemia, Myeloid; Liver; Male; Middle Aged; Myeloproliferative Disorders; Preleukemia; Tretinoin

The HL-60 cell line, derived from a patient with acute promyelocytic leukemia, proliferates continuously in suspension culture and consists predominantly (greater than 90%) of promyelocytes. These cells can be induced to differentiate to morphologically and functionally mature granulocytes by incubation with a wide variety of compounds, including butyrate and hypoxanthine and polar planar compounds such as dimethyl sulfoxide and hexamethylene bisacetamide. We have now found that retinoic acid (all-trans-retinoic acid) induces differentiation (as measured morphologically and by the ability to reduce nitroblue tetrazolium) of HL-60 at concentrations as low as 1 nM. Maximal differentiation (approximately 90%) occurs at 1 micro M, a concentration 1/500th to 1/160,000th the concentrations of butyrate (0.5 mM) and dimethyl sulfoxide (160 mM) that promote a similar increase in differentiation. Continuous exposure to retinoic acid is necessary for optimal differentiation, with the percentage of mature cells in the culture directly related to the length of time of exposure to retinoic acid. Retinoic acid and 13-cis-retinoic acid are equally effective in inducing differentiation of HL-60. Retinol (vitamin A), retinal, and retinyl acetate are approximately 1/1000th less potent. This study suggests that retinoids could provide a therapeutic tool in the treatment of acute myeloid leukemia, a disease that has been looked upon as primarily involving a block in myeloid differentiation, and indicates that retinoids, in addition to their well-characterized involvement in epithelial cell differentiation, may also be involved in the differentiation of certain hematopoietic cells.

Topics: Cell Differentiation; Cell Division; Cells, Cultured; Dose-Response Relationship, Drug; Granulocytes; Hematopoiesis; Humans; Leukemia, Myeloid; Phagocytosis; Preleukemia; Structure-Activity Relationship; Time Factors; Tretinoin