Chemopreventive role of soybean peptides against cancer

Cancer is one of the most common causes of death in developed countries. Its incidence and mortality rates are increasing, thus cancer has become the medical challenge of this century. Accumulating evidence supports the vital role of lifestyle changes in cancer prevention and control. It has been estimated that at least 35% of all cancer deaths are associated with dietary factors. Epidemiological studies have linked soybean consumption with low incidences rates of an array of chronic diseases, including cardiovascular disorders and cancer. Over the past decades, a remarkable number of cell culture, animal experiments and human trials focused to support this association between soy consumption and lower cancer risk has been conducted. Among soybean compounds exerting chemopreventive properties, isoflavones and peptides are most extensively studied. This review summarizes the effects of soybean protease inhibitors and lectins against cancer, also mentions their demonstrated mechanisms of action. Special attention is given to peptide lunasin, discovered in our laboratory twelve years ago, whose verified properties make it a promising alternative for cancer prevention and/or therapy. Its chemopreventive activity revealed by in vitro and in vivo models, as well as its bioavailability and mechanism of action are included in this chapter.