Primary acute myeloid leukemia cells negative for c-kit receptor protein expression do not proliferate in vitro in response to colony-stimulating factors.

This study examined the effects of recombinant human stem cell factor (SCF) alone or in combination with colony-stimulated factors (CSFs) on colony formation of leukemic progenitors obtained from 29 acute myeloid leukemia (AML) patients. C-kit receptor (c-kitR) protein expression was examined using an immunofluorescence method and was detected on more than 10% of leukemic cells in 20 of 29 cases (c-kitR+). SCF alone could stimulate formation of colonies in 14 of 20 c-kitR+ cases. Granulocyte(G)-CSF, granulocyte-macrophage (GM)-CSF, and interleukin (IL)-3 alone stimulated colony growth in 18, 17 and 16 of c-kitR+ cases, respectively. In contrast, colony and cluster formations from eight of nine c-kitR- cases was not stimulated at all by SCF alone nor SCF in combination with CSF nor with any CSF alone. However, the in vitro culture behavior of fluorescence-activated cell sorter-sorted c-kitR- cells from c-kitR+ cases did not significantly differ from c-kitR+ cells. These results suggest that responses of leukemic progenitors to CSFs were variable but may be predicted by their c-kitR expressions, and that c-kitR(-) cases may have a different disease entity from c-kitR(+) cases.