ACTIVITY OF FGR PROTEIN-TYROSINE KINASE IS REDUCED IN NEUTROPHILS OF PATIENTS WITH MYELODYSPLASTIC SYNDROMES AND CHRONIC MYELOGENOUS LEUKEMIA

The Fgr protein-tyrosine kinase, p55(c-fgr), is specifically expressed and functions in cells of myelomonocytic lineages. We examined levels of expression and enzymatic activity of p55(c-fgr) peripheral blood n eutrophils of patients with myelodysplastic syndromes (MDS) and chroni c myelogenous leukemia (CML) by comparison with those of normal indivi duals. While neutrophils of eight normal subjects gave uniform results , the specific enzymatic activity of p55(c-fgr), a ratio of the total kinase activity versus the protein level was reduced in seven out of e ight patients with MDS and all of five patients with CML. The specific kinase activity of p55(c-fgr) correlated significantly with the activ ity of neutrophil alkaline phosphatase (NAP) which has been considered to be a marker of neutrophil maturity (r=0.568, P<0.01), The reduced activity of this tyrosine kinase was considered to be a biological par ameter for immaturity and to reflect dysfunction of neutrophils of pat ients with MDS and with CML. Copyright (C) 1996 Elsevier Science Ltd.