Enhancement of clonal proliferation of mouse mast cells by a tumor-promoting phorbol ester

Mast cell colonies grew in methylcellulose when mouse spleen cells were cultured for 14 days in the presence of medium conditioned by concanavalin A-stimulated spleen cells. Tumor-promoting phorbol esters, 12-O-tetradecanoylphorbol-13-acetate (TPA) and phorbol-12,13-didecanoate, enhanced the concanavalin A-stimulated spleen cell-conditioned medium-induced colony growth of mast cell progenitors. The effect of TPA on this colony growth was blocked by the addition of two antipromoters of experimental skin carcinogenesis, i.e., retinoic acid and dexamethasone. These results show that TPA has the ability to enhance the clonal proliferation of mouse mast cells and that this effect of TPA is closely related to tumor-promoting activity.