Human myelogenous leukemia: enhanced clonal proliferation in the presence of phorbol diesters.

Phorbol diesters, including 12-0-tetradecanoyl-phorbol-13-acetate (TPA) at low concentrations, enhanced the clonal proliferation of a human myelogenous leukemia cell line (KG-1). TPA (1.0 X 10(-9) -5.0 X 10(-11) M) increased KG-1 clonal growth by four to tenfold in the presence of suboptimal concentrations of colony stimulating factor (CSF) and by two to fourfold in the presence of maximally stimulating concentrations of CSF. The ability of TPA analogs to enhance KG-1 clonal growth paralleled their reported ability to promote tumors in mice. Only slight CSF activity was detected in the conditioned medium from KG-1 cells cultured in liquid medium with TPA. TPA was unable to increase myeloid clonal growth of CSF-stimulated normal human model to study TPA enhancement of CSF-stimulated growth.