The c-kit molecule and the surface immunophenotype of human acute leukemia

The proto-oncogene c-kit encodes the receptor for a stem cell factor (c-kit molecule). Expression of the c-kit molecule on the gated leukemic blast cells from newly diagnosed patients with leukemia was analysed by flow cytometry using the monoclonal antibody (17F11). Among 35 myeloid leukemia cases examined, significant c-kit-positive blast cells were detected in 24 cases (69%), even though the percentage of positive cells was widely variable. The correlation between the percentage of cells positive for the c-kit molecule and the percentage of cells positive for CD34 was found to be statistically significant (rs = 0.36, p < 0.05). Fifteen cases of myeloid leukemia were positive for lymphoid markers. The mean percentage of the cells expressing c-kit molecule among the lymphoid marker-positive cases was significantly larger than that among the lymphoid marker-negative cases (p < 0.05). All 19 lymphoid leukemia cases were c-kit-negative, including 8 cases which were positive for some myeloid markers. Stem cell factor enhanced the colony growth in five out of six acute myeloblastic leukemia cases expressing the c-kit molecule. On the other hand, SCF did not stimulate colony growth in any of the four cases which were not positive for the c-kit molecule. These findings indicated that the distribution of flow cytometrically detectable c-kit molecules on leukemic cells is related to the morphologic and immunologic classification of these leukemic cells and to the expression of the CD34 cell surface molecule on some myeloid leukemic cells. On such cells, expression of the c-kit molecule may have a functional role and be related to the maturation process.