• 1 January 1978
    • journal article
    • research article
    • Vol. 38  (5) , 1434-1437
Abstract
In vitro systems that are responsive to tumor-promoting agents may facilitate the identification of such agents and the analysis of their mode of action. The potent tumor promoter phorbol-12-myristate-13-acetate induces synthesis of plasminogen activator in cultured chick embryo fibroblasts. Various compounds were tested for their ability to induce plasminogen activator in chicken embryo fibroblasts. Among these, phorbol esters and other macrocyclic diterpene esters isolated from species of the families Euphorbiaceae and Thymelaeaceae were potent inducers of plasminogen activator. These compounds maximally induced enzyme to the same levels, although they differed in their relative molar potencies. Structural requirements for in vitro activity paralleled the requirements for activity in vivo. These results indicate that induction of plasminogen activator is a useful marker for the biologically active macrocyclic diterpene esters. Tumor-promoting agents such as anthralin, cantharidin, Tween 60 and tobacco leaf extract failed to induce plasminogen activator.