Reaching to Soy for Cancer Resolution

Both incidence rate and death rate from cancer declined from 1999–2006, according to the most recent analysis (Edwards, B.K. et al., 2010). The leading contributors to these important statistics reflect a significant drop in three cancers common to men (lung, prostate, and colorectal) and two of the three cancers common among women (breast, colorectal).

This decline may reflect several aggressive prophylactic interventions, namely increased screening, reduction in risk factors, and improved therapeutics. It is also important to attribute it to numerous dietary components such as the consumption of soyrich foods. The positive health effects of dietary soy led to the FDA recommendation for increased soy protein intake to reduce cardiovascular disease risk.

About the time FDA issued the soy recommendation, additional research led investigators to the identification and characterization of functional properties of lunasin, a bioactive soy peptide (Kennedy A.R., 1995). Many bioactive dietary components survive digestion and enter the circulation and trigger cellular response by mechanisms such as binding to a membrane receptor, which triggers a series of kinase phosphorylation reactions, which may affect gene expression. Other agents enter the cell directly and move to the nucleus to act as transcription factors, coactivators, etc., which direct the specific region of DNA to be expressed, synthesizing key proteins to alter metabolism.

Lunasin is found in soy, rice, lima beans, red kidney beans, and an array of monocotyledonous and dicotyledonous seeds that appear to function as a unique protease inhibitor, specifically a Bowman-Birk protease inhibitor (BBI). This type of molecule inhibits proteases involved in the initiation and promotion of carcinogenesis. In vitro studies indicate that this 43-amino acid peptide from soybeans may reduce cellular transformations induced by oncogenes through several carcinogenic pathways (Ledesma-Hernández, B. et al., 2009).

Lunasin from other dietary sources, such as cereal grains barley and wheat, appears to be equally effective in inhibiting oncogene expression and chemically induced carcinogenogenesis and arrests mitosis while inducing apoptosis in malignant cells (Jeong, H.J. et al., 2009; Galvez, A.F. and de Lumen, B.O., 2001). Studies have indicated that lunasin inhibits mitosis of cancer cells by binding to the chromatin, thereby disrupting DNA duplication. Further investigations demonstrated lunasin has an internal tripeptide cell adhesion region that can selectively bind to transfected cells and subsequently inhibit histone acetylation during transformation. In some cases, this is a pivotal biological process in tumor growth or tumor suppression. In this case, lunasin appears to suppress tumor expansion (Galvez, A.F. et al., 2001).

In vitro and in vivo studies indicated lunasin is resistant to classic gastrointestinal digestion as well as degradation by serum proteinases and peptidases. Two excellent recent review articles on food-derived Bowman-Birk inhibitors reported lunasin survives normal digestive processes, enters into the circulation, and can be found in an array of tissue targets (Losso, J.N., 2008; Magbanua, M.J.M. et al., 2006). Lunasin may up regulate genes responsible for tumor suppression, including the erbb2 gene which suppresses Ras signaling. This is particularly important since mutation of the Ras oncogene appears to be responsible for about 30% of human cancers (Duursma, A.M. and Agami, R., 2003). Of course, cancer cell sensitivity to lunasin is not consistent across all transformed cell lines, including some forms of prostate and breast cancer, yet may interact syner-gistically with other dietary components such as isoflavones, thereby potentially reducing the growth and survival of these kinds of cells.

Foods contain a variety of compounds that influence human health. Many of these compounds modulate our immune system through the up regulation and down regulation of various genes that impact an array of inflammatory substances. It appears that lunasin and similar dietary peptides exert antiinflammatory properties (de Majia, E.G. and Dia, V.P., 2009). Considering that chronic diseases such as cardiovascular disease, diabetes, and cancer manifest their dastardly impact through inflammation processes, it is incumbent that additional research focus on the potential role of dietary components such as lunasin in an effort to reduce the incidence and effects of these disorders and to influence personal dietary practices and public health guidelines.

References for the studies cited in this article are available from the authors.

by Roger Clemens, Dr.P.H.,
Contributing Editor
Scientific Advisor, ETHorn, La Mirada, Calif.
[email protected] 

by Wayne Bidlack, Ph.D.,
Contributing Editor
Professor, California State Polytechnic University, Pomona 
[email protected]