Paradoxical anti‐leukemic effects of plant‐derived tumor promoters on a human thymic lymphoblast cell line

Three different diterpen polyols and the teleocidin have antileukemic effects on the human thymic leukemia cell line HPB‐ALL by inducing phenotypic differentiation. We tested TPA (phorbol esters), mezerein (daphnane), milliamin (ingenol ester) and teleocidin B (teleocidins) as representative of the chemical structure of each principle and found that these agents have the similar biological activity of inducing phenotypic differentiation in HPB‐ALL cells. Moreover, competitive binding of [³H]PDB to cell‐surface receptors was significantly inhibited by these agents; n‐butyrate and phorbol per se did not inhibit the binding of [³H]PDB. Despite differences in the structure of the principles, these agents may have similarly acting side‐chain structures.