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Granulocyte-macrophage colony-stimulating factor is an endogenous regulator of cell proliferation in juvenile chronic
R J Gualtieri1, P D Emanuel, K S Zuckerman
1Department of Medicine, Children's Hospital of Alabama, Birmingham.
Insights
Juvenile chronic myelogenous leukemia (JCML) involves abnormal growth of blood cells due to endogenous growth factors. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is identified as the primary driver of this malignant proliferation in children.
Area of Science:
- Hematology
- Pediatric Oncology
- Molecular Biology
Background:
- Juvenile chronic myelogenous leukemia (JCML) is a rare childhood myeloproliferative disorder distinct from adult chronic myeloid leukemia.
- JCML exhibits spontaneous growth of hematopoietic progenitors from peripheral blood, independent of external stimuli.
- This spontaneous growth is linked to the production of endogenous growth factors by malignant cells.
Purpose of the Study:
- To investigate the specific endogenous growth factors responsible for the aberrant proliferation in JCML.
- To determine the role of various colony-stimulating factors (CSFs) and cytokines in JCML pathogenesis.
Main Methods:
- Utilized peripheral blood mononuclear cells (PBMNCs) from seven children with JCML.
- Employed a 3H-thymidine incorporation assay to measure cell proliferation.
- Tested the effects of neutralizing antisera and monoclonal antibodies against GM-CSF, G-CSF, M-CSF, IL-3, IL-1, and TNF.
- Assessed growth factor production by enriched JCML monocytes using monocyte-conditioned medium (MCM).
Main Results:
- Antisera and monoclonal antibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF) significantly inhibited JCML cell proliferation (up to 72%).
- GM-CSF neutralization also markedly inhibited spontaneous growth of peripheral blood CFU-GM derived colonies (87-90% inhibition).
- JCML monocyte-conditioned medium showed variable levels of IL-1-like activities and, in one case, high GM-CSF, potentially secondary to IL-1.
Conclusions:
- Granulocyte-macrophage colony-stimulating factor (GM-CSF) is the primary endogenous regulator of JCML cell proliferation.
- JCML may result from paracrine stimulation of progenitor cells by growth factors secreted by malignant monocytes.
- These findings highlight GM-CSF's critical role in the pathogenesis of this pediatric leukemia.
Abstract:
Juvenile chronic myelogenous leukemia (JCML) is a rare myeloproliferative disorder of early childhood that is clinically and cytogenically distinct from the well-recognized adult type of chronic myeloid leukemia. Unlike the adult disease, growth of hematopoietic progenitors from peripheral blood (PB) occurs in the absence of exogenous stimulus even at low cell densities. This so-called "spontaneous" growth can be abrogated by adherent cell depletion and appears to depend on production of endogenous growth factors. We studied seven children with JCML to determine the nature of endogenous stimulators. With isolated PB mononuclear cells (PBMNCs) and a 3H-thymidine (3H-TdR) incorporation assay, JCML cells were shown to incorporate high levels of 3H-TdR when cultured in the absence of stimulus even at low cell densities. When neutralizing antisera prepared against each of the four known colony-stimulating factors (CSFs), GM-CSF, G-CSF, M-CSF, and interleukin-3 (IL-3), as well as antisera against interleukin-1 (alpha and beta) and tumor necrosis factor (TNF) were added to these cultures, only the antisera against recombinant human GM-CSF (rhGM-CSF) consistently resulted in significant inhibition of cell proliferation, achieving up to 72% inhibition of 3H-TdR incorporation in one case. Monoclonal antibodies (MoAbs) against rhGM-CSF resulted in a similar and highly significant degree of inhibition. A marked inhibitory effect of rhGM-CSF antiserum on "spontaneous" growth of PB CFU-GM derived colonies in semisolid medium was also demonstrated in four of five patients studied (87% to 90% inhibition). Production of growth factors by highly enriched JCML monocytes was variable. When initially studied in five of the seven patients, the monocytes from three of the patients revealed increased release of IL-1-like activities; two patients had levels similar to those of controls. One patient with normal levels when initially studied was later shown to have markedly increased amounts of IL-1-like activities in a second preparation of monocyte-conditioned medium (MCM). High levels of GM-CSF were detected in the initial MCM from one patient, but this may have indirectly reflected elevated IL-1-like activities present in the MCM. IL-3 and M-CSF levels were either low or undetectable in the patients studied as compared with MCM prepared with normal adult monocytes. These results clearly implicate GM-CSF as the primary endogenous regulator of JCML cell proliferation in culture and suggest that this malignant myeloproliferative disease may in part result from paracrine stimulation of marrow progenitor cells by growth factors/cytokines secreted by the malignant monocytes.