Tumor cell killing by phorbol ester--differentiated human leukemia cells.

The tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate causes differentiation of cells of the human leukemia cell line HL60 to nondividing macrophage-like cells. These differentiated cells are cytotoxic for tumor cells (including parent, untreated HL60 cells) in vitro. Agents that induce this desirable differentiation to nondividing, antitumor effector cells may be useful in the experimental treatment of leukemia.