Neutrophil function and cytokine-specific signaling in chronic neutrophilic leukemia

We diagnosed an 86-year-old woman with chronic neutrophilic leukemia (CNL) because she showed sustained leukocytosis dominated by mature neutrophils, hepatosplenomegaly, high neutrophilic alkaline phosphatase score, absence of the Ph chromosome, low serum level of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF), and no evidence of leukemoid reaction. We found that the extent of stimulation of her neutrophil functions by G-CSF and GM-CSF was greatly reduced compared to healthy donars neutrophils. We showed that CNL neutrophils have intact expression of granulocyte colony-stimulating factor receptor (G-CSFR) and granulocyte-macrophage colony-stimulating factor receptor (GM-CSFR). This suggests that failure of enhancement by G-CSF and GM-CSF in CNL neutrophil functions might be due to disturbances in the intracellular domains of G-CSFR and GM-CSFR, regardless of external cytokine stimulation. However, the patient's neutrophils did not show any mutations in the G-CSFR and GM-CSFR intracellular critical regions. We also showed that stat3 and mitogen-activated protein kinase activation by G-CSF or GM-CSF in the patient's neutrophils were significantly lower than those in healthy donor neutrophils. These results suggest that deficiency of CNL neutrophil function might be due to insufficiency of some inflammatory cytokine-specific signaling. Hence, we are the first to show that CNL neutrophils have partially insufficiency in some cytokine-specific signaling. Further studies are needed to elucidate the signal transduction pathways relating to functional defects in CNL neutrophils.