Tumor-promoting agents from Croton tiglium L. and their mode of action.

The isolation of chemically pure tumor-promoting agents from croton oil in this laboratory facilitated the exploration of a number of areas concerning their mode of action and the role of tumor-promoting agents in chemical carcinogenesis. Our recent studies have centered on the mode of action of these phorbol esters on cellular and intracellular membranes. The use of tumor-promoting agents in two areas of carcinogenesis studies are also described in this report. They are: inhibition of tumorigenesis in two-stage carcinogenesis and the relationship between initiating agents, mutagens, and carcinogens.