Protease inhibitors (PIs), which are widely distributed in plants and animals and have a variety of functions, interfere with cancer development in a number of ways, including suppression of oxygen radicals, oncogenes, and metastases. Epidemiologic evidence supports their prevention of major human c

Protease inhibitors (PIs) are widely distributed in plants and animals, and have a variety of functions, which include preventing digestion of seeds by insects and modifying blood clotting in animals. After it was noted that synthetic and natural inhibitors suppress two-stage carcinogenesis and breast cancer, extensive work investigating PIs as chemopreventive agents was started. PIs are unique in that they interfere with cancer development in a variety of ways, including suppression of oxygen radicals, oncogenes, and metastases. Epidemiologic evidence supports their prevention of major human...