The Effects of Tumor-Promoting Phorbol Esters on Human Granulopoiesis In Vitro

In order to determine whether the tumor-promoting phor-bol esters are capable of inducing normal human commit-ted granulocytic-monocytic progenitor cells (CFUc) to proliferate and differentiate in the absence of granulocyte-monocyte colony-stimulating activity (CSA). we studied the effects of these compounds on human granulopoiesis in vitro. We found that when light-density human marrow cells or peripheral blood leukocytes were depleted of adherent cells and then incubated in semisolid tissue culture medium under conditions optimal for CFUc growth. phorbol myristate acetate (PMA) and its congeners pro-duced no measurable stimulatory effect on the prolifera-tion of CFUc in the absence of added CSA. Likewise. when light-density marrow cells that had not been depleted of adherent cells were plated in the cultures. no stimulation o