Juvenile and adult types of chronic granulocytic leukemia of childhood: growth patterns and characteristics of granulocyte-macrophage colony forming cells

Induced Pluripotent Stem Cells to Model Juvenile Myelomonocytic Leukemia: New Perspectives for Preclinical Research

Juvenile myelomonocytic leukemia (JMML) is a malignant myeloproliferative disorder arising in infants and young children. The origin of this neoplasm is attributed to an early deregulation of the Ras signaling pathway in multipotent hematopoietic stem/progenitor cells. Since JMML is notoriously refractory to conventional cytostatic therapy, allogeneic hematopoietic stem cell transplantation remains the mainstay of curative therapy for most cases. However, alternative therapeutic approaches with small epigenetic molecules have recently entered the stage and show surprising efficacy at least in specific subsets of patients. Hence, the establishment of preclinical models to test novel agents is a priority. Induced pluripotent stem cells (IPSCs) offer an opportunity to imitate JMML ex vivo, after attempts to generate immortalized cell lines from primary JMML material have largely failed in the past. Several research groups have previously generated patient-derived JMML IPSCs and successfully differentiated these into myeloid cells with extensive phenotypic similarities to primary JMML cells. With infinite self-renewal and the capability to differentiate into multiple cell types, JMML IPSCs are a promising resource to advance the development of treatment modalities targeting specific vulnerabilities. This review discusses current reprogramming techniques for JMML stem/progenitor cells, related clinical applications, and the challenges involved.

Congenital juvenile chronic myelogenous leukemia: therapeutic trial with interferon alpha-2

A newborn with congenital juvenile chronic myelogenous leukemia (JCML) is described. The diagnosis was suggested by the characteristic clinical and hematologic presentation, and was confirmed by the results of in-vitro cultures of the hematopoietic progenitors, which showed excessive proliferation of monocytic colonies, with and without the addition of exogenous granulocyte-macrophage colony stimulating factor (GM-CSF). Based on published in-vitro response of JCML cells to alpha interferon-2 (alpha IFN 2), we treated this child for 17 weeks with subcutaneous alpha interferon, 1,000,000 units per day. In contrast to previous in vitro results, treatment of this patient affected neither the clinical course of the disease, nor the in vitro growth of the peripheral blood-derived monocytic colonies.

Interleukin 1-dependent paracrine granulopoiesis in chronic granulocytic leukemia of the juvenile type

Marrow and peripheral blood cells from nine children with juvenile chronic granulocytic leukemia (JCGL) demonstrated intense (94 +/- 16% maximum) spontaneous granulocyte/macrophage colony growth but cells from five children with the adult variety of CGL did not. This unusual pattern of colony growth depended upon a stimulatory protein(s) produced by mononuclear phagocytes. No GM-CSA activity was found in any chromatofocused fraction of JCGL monocyte-conditioned media but an activity that induced GM-CSA in umbilical vein endothelial cells was detected at pI 6.9-7.2. Moreover, the CSA-inducing monokine was neutralized by an anti-IL-1 antibody in vitro and, in the one case so tested, the same antibody also inhibited "spontaneous" colony growth. Therefore granulocyte/macrophage colony growth in JCGL is characteristically abnormal and distinguishes JCGL from the adult form of the disease. This abnormality depends upon the production, by mononuclear phagocytes, of IL-1 which, in turn, stimulates the release of high levels of colony stimulating activity by other cells. The high proliferative activity of CFU-GM we found in JCGL patients, and the high levels of GM-CSA found in their serum are compatible with the view that the in vitro abnormality reflects a similar abnormality in vivo.

The production of myeloid blood cells and their regulation during health and disease

The regulation of myelopoiesis in vivo most likely entails a complex set of interactions between cell-derived biomolecules and their target cells: hematopoietic stem and progenitor cells and accessory cells. Stimulating and suppressing factors have been characterized through in vitro studies, and their mechanisms of action in vitro and in vivo have begun to be elucidated. Among those factors being studied are the hematopoietic colony-stimulating factors (CSF): interleukin-3 (multi-CSF), granulocyte-macrophage-CSF, granulocyte-CSF, and macrophage-CSF; other molecules include erythropoietin, B-cell-stimulating factor-1, interleukin-1, interleukin-2, prostaglandin E, leukotrienes, acidic ferritins, lactoferrin, transferrin, the interferons-gamma, -alpha, and -beta, and the tumor necrosis factors-alpha and -beta (lymphotoxin). These factors interact to modulate blood cell production in vitro and in vivo. The proposed review characterizes these biomolecules biochemically and functionally, including receptor-ligand interactions and the secondary messengers within the cell which mediate their functional activity. The production and action of the molecules are described under conditions of hematopoietic disorders, as well as under normal conditions. Studies in vitro are correlated with studies in vivo using animal models to give an overall view of what is known about these molecules and their relevance physiologically and pathologically.

Juvenile features in adult-type chronic granulocytic leukemia

Philadelphia chromosome (Ph1) positive, or "adult-type," chronic granulocytic leukemia (CGL) differs in many clinical and laboratory aspects from PH1-negative, or "juvenile," CGL. Because of these differences, the disorders have been considered two distinct disease entities. We present a child with Ph1-positive CGL whose disease has several features more characteristic of the Ph1-negative syndrome. This case demonstrates that the chromosomal anomaly in CGL is not always predictive of phenotypic expression in this disease.

Colony assays of hematopoietic progenitor cells and correlations to clinical situations

The production of blood cells is a dynamic process that is noticeably aberrant during disease. The availability of colony assays in vitro that allow detection of hematopoietic stem and progenitor cells for the neutrophil, monocyte-macrophage, erythroid and/or megakaryocyte lineages has been of importance for the present understanding of the mechanisms controlling the proliferation, self-renewal capacity, and differentiation of morphologically nonrecognizable immature cells which give rise to the mature progeny circulating in the blood. It is through the use of these assays that the existence of potentially relevant stimulatory and inhibitory feedback interactions has been demonstrated. Abnormalities in these interactions, which may be of significance during leukemia and related disorders, have been uncovered. This communication will discuss regulatory interactions detected via the colony assays, their potential relevance physiologically and pathologically, and the use of these assays for diagnosis, prognosis, and for monitoring the clinical status of patients.