HETEROGENEOUS EFFECTS OF G-CSF AND GM-CSF ON CELL-GROWTH AND ARA-C CYTOTOXICITY IN CHILDHOOD LEUKEMIAS WHICH EXPRESS MYELOID MARKERS

It is uncertain if acute lymphoblastic leukemia (ALL) cells expressing myeloid makers can respond to granulocyte colony-stimulating factor ( G-CSF) and granulocyte macrophage colony-stimulating factor (GM-CSF). We investigated the effects of G-CSF (0.01 mu g/ml) and GM-CSF (0.01 m u g/ml) on [H-3]thymidine (TdR) uptake, and the cytotoxicity of 1-beta -D-arabinofuranosylcytosine (ara-C) in leukemia cells from 17 pediatri c patients. ALL cells without myeloid markers did not respond to G-CSF or GM-CSF, On the other hand, these cytokines enhanced the [H-3]TdR u ptake and cell growth, not only of AML cells but also of ALL cells exp ressing myeloid antigens. However, G-CSF and GM-CSF did not always enh ance the growth inhibitory effect of the cell cycle specific drug ara- C when the cells were co-cultured with the drug. There was no relation ship between cell growth and the amount of [H-3]TdR incorporation or t he intracellular ara-CTP level. These results indicate the heterogeneo us effects of G-CSF and GM-CSF on cell growth and ara-C sensitivity in childhood leukemia cells.