INHIBITION OF ERYTHROID-DIFFERENTIATION BY STEM-CELL FACTOR IN K562 CELLS EXPRESSING THE C-KIT GENE

We found a K562 subclone (K562YO) that highly expressed the c-kit gene. K562YO had a higher capability of erythroid differentiation by hemin and cytosine arabinoside (Ara-C) than its parent K562 (KIT-). We obtained the transfectant expressing c-kit by introducing c-kit cDNA into K562 (KIT-) The differentiation of the transfectant was similar to that of the parent cell. Thus the difference described above was not due to the expression of c-kit. Next, we investigated the effects of stem cell factor (SCF) on the differentiation of the K562 cell expressing c-kit. SCF did not enhance the cell growth of K562YO. On the other hand, SCF suppressed induction of benzidine-positive cells when c-kit-positive cells were treated with hemin and Ara-C, especially at a low concentration. Furthermore, c-kit mRNA and protein were downregulated during erythroid differentiation. SCF also downregulated the c-kit proteins. Our results suggest that the SCF/c-kit signals could act negatively for erythroid differentiation of the K562 cells expressing c-kit. K562YO is also useful for studying the mechanism that controls the expression of the c-kit gene because there is a K562 counterpart cell line that does not express this gene.