Effect of phorbol ester on differentiation of human myeloid colony forming cells (CFU-C)

The effects of 12-O-tetradecanoyl phorbol-13-acetate (TPA) on CFU-C were investigated. Exposure of normal bone marrow cells or peripheral blood cells from chronic myeloid leukemia patients to TPA stimulated cluster formation in agar in the absence of added colony-stimulating factors (CSF). In the presence of CSF, TPA inhibited colony and cluster formation. After enrichment of CFU-C approx. 50-fold by an immune rosette technique, TPA-induced stimulation of cluster formation in the absence of CSF was markedly diminished, while the inhibitory effect in the presence of CSF was unchanged. These results suggest that TPA may have complex effects on CFU-C; indirectly promoting colony formation by inducing other cells to secrete CSF, and directly inhibiting CFU-C proliferation.