Elevated expression of the proto-oncogene c-kit in patients with mastocytosis

The stem cell factor (SCF)c-kit receptor interaction plays a critical role in the development and survival of mast cells. Several studies have also associated c-kit receptor mutations with the human diseases, mastocytosis and piebaldism. Overexpression of c-kit has been reported to be associated with myeloproliferative disorders and myelodysplastic syndromes. Using peripheral blood mononuclear cells (PBMCs) from 11 patients with indolent mastocytosis (category I), mastocytosis with an associated hematologic disorder (category II), or aggressive mastocytosis (category III); a patient with CMML unassociated with mastocytosis, and PBMCs from 13 normal subjects, we examined the level of expression of c-kit mRNA along with other c-kit isoforms to determine if overexpression of the c-kit receptor was associated with mastocytosis. Using quantitative competitive PCR, c-kit mRNA levels on average were found to be statistically elevated in the five patients with mastocytosis with an associated hematologic disorder and in the patient with aggressive mastocytosis as compared with controls, but not elevated in patients with indolent mastocytosis. The relative mRNA expression for the two c-kit isoforms was not significantly different in the mastocytosis patients compared with controls. This demonstration of the overexpression of c-kit mRNA in mastocytosis, and particularly those patients with clinical evidence of myelodysplastic syndrome, adds evidence to support the conclusion that mastocytosis, at least in some patients, is a feature of myelodysplasia; and suggests that determination of c-kit mRNA expression in PBMCs may provide an additional approach to assessing prognosis.