Chronic myelomonocytic leukemia (CMML) and juvenile myelomonocytic leukemia (JMML) are myelodysplastic syndrome (MDS)/myeloproliferative neoplasm (MPN) overlap disorders characterized by monocytosis, myelodysplasia, and a characteristic hypersensitivity to granulocyte-macrophage colony-stimulating factor (GM-CSF).
Juvenile myelomonocytic leukemia (JMML) is an aggressive leukemia of early childhood characterized by aberrant proliferation of myelomonocytic cells and hypersensitivity to GM-CSF stimulation.
Leukemia cells from patients with juvenile myelomonocytic leukemia display hypersensitivity to certain cytokines, such as granulocyte-macrophage colony-stimulating factor.
Juvenile myelomonocytic leukaemia (JMML) is an aggressive myeloproliferative neoplasm in children characterized by granulocyte macrophage colony-stimulating factor (GM-CSF) hypersensitivity and resistance to chemotherapy.
Notably, dasatinib, an U.S. Food and Drug Administration-approved multikinase inhibitor that also targets Src family, dramatically attenuated the spontaneous and GM-CSF-induced hypersensitive growth phenotype of mononuclear cells from peripheral blood and bone marrow collected from JMML patients harboring Cbl or other known JMML-associated mutations.
In vitro differentiation of JMML iPSCs produced myeloid cells with increased proliferative capacity, constitutive activation of granulocyte macrophage colony-stimulating factor (GM-CSF), and enhanced STAT5/ERK phosphorylation, similar to primary JMML cells from patients.
Juvenile myelomonocytic leukemia is a lethal disease of children characterized by hypersensitivity of hematopoietic progenitors to granulocyte macrophage-colony stimulating factor.
Mutations in RAS, neurofibromatosis type 1 (NF1), and PTPN11, constituents of the granulocyte-macrophage colony-stimulating factor signaling pathway, have been recognized in patients with juvenile myelomonocytic leukemia (JMML).
Specific defects in the RAS signalling pathway, which make JMML cells hypersensitive to granulocyte-macrophage colony-stimulating factor, are observed in at least two-thirds of patients with JMML: inactivation of NF1 or mutations in NRAS, KRAS2 or PTPN11.
With this quantification method, JMML patients with RAS mutations showed significantly higher GM-CSF sensitivity than JMML patients with PTPN11 mutations.
These data indicate that SHIP-1 can effectively block GM-CSF hypersensitivity in JMML progenitor cells with mutations in KRAS2 or PTPN11 and may be a useful approach for the treatment of JMML patients.
Mutations in SHP-2 phosphatase that cause hyperactivation of its catalytic activity have been identified in human leukemias, particularly juvenile myelomonocytic leukemia, which is characterized by hypersensitivity of myeloid progenitor cells to granulocyte macrophage colony-stimulating factor and interleukin (IL)-3.
These data support the hypothesis that PTPN11 mutations induce hematopoietic progenitor hypersensitivity to GM-CSF due to hyperactivation of the Ras signaling axis and provide a basis for the GM-CSF signaling pathway as a target for rational drug design in JMML.
Hypersensitivity for granulocyte-macrophage colony-stimulating factor and pathologic activation of the Ras/MAPK pathway play an important role in the pathophysiology of juvenile myelomonocytic leukemia and provide the opportunity for several novel therapeutic approaches.
The stimulatory effect of TNF on GM-CSF gene expression in JMML cells probably takes place at the transcription level, because the ribozyme treatment decreased GM-CSF mRNA.
The selective sensitivity to DT388-GM-CSF of leukemic progenitors from a majority of JMML and CMML patients suggests that this agent could have therapeutic potential for some patients with these diseases.