Cocarcinogens and Tumor Promoters and Their Environmental Importance

In recent years a great deal of effort has been spent on uncovering new carcinogens and studying the mode of action of well-known carcinogens such as nitroso compounds, aromatic hydrocarbons and aromatic amines and their occurrence in air, water, foods and other environmental sources. It has been known for about thirty years that some materials, while non-carcinogenic, can enhance greatly the potency of low-levels of known environmental carcinogens. The first such material to be discovered was the tumor promotor, croton oil, derived from the seeds of a tropical plant, Croton tiglium L, indigenous to India and Sri Lanka. Researchers interested in chemical carcinogenesis have examined its unusual behavior for many years. The active principles of croton oil, the phorbol esters, were finally isolated and chemically characterized. Recently these phorbol esters have become widely available. Consequently, their effects have been examined in a wide range of biochemical and biological studies. The phorbol esters a...