Lyndon L. Larcom, Departments of Biological Sciences and Physics, Clemson University, Clemson, SC 29634-0978
Diets high in fruits and vegetables are protective against cancer. Numerous in vitro studies have demonstrated activity of various extracts against different aspects of the tumorigenic process. Plants and their fruits are extremely complex and their chemical compositions can depend on the variety, on culture conditions such as soil composition, lighting, pesticide treatment and on ripeness at the time of harvest, processing techniques and storage. Numerous data indicate that berries possess anti-cancer characteristics when tested by various assays in vitro. However to use berries or berry extracts in the most effective way for cancer prevention, the aforementioned parameters must be optimized. Our first approach to this was to determine whether different varieties might vary in their effects on genetic damage produced by carcinogens. If this is the case, those varieties with the greatest effects should be used for animal tests. In addition, comparison of the chemical analyses of the most effective varieties with the less effective ones could help identify the active groups of compounds.
The initial step in tumor formation is the production of a somatic mutation in a gene involved in control of cell division or in maintaining the integrity of genetic information. This damage can be the result of insult by an exogenous carcinogen or by active species generated by metabolism of the cell itself. We have compared eight varieties of blackberry for their abilities to suppress mutagenesis induced by a direct-acting carcinogen, a carcinogen which requires metabolic activation, and by ultraviolet radiation. None of the varieties significantly suppressed mutagenesis by the direct-acting mutagen methyl methanesulfonate but all strongly inhibited mutagenesis by 2-amino anthracene, a potent carcinogen which must be metabolized to become mutagenic.
In contrast to the results obtained with the chemical carcinogens, the different varieties differed greatly in their effects on mutagenesis induced by UV radiation. While the Arapaho and Choctaw varieties had essentially no effect on UV-induced mutagenesis, Chester suppressed mutagenesis by 85% and Navajo caused 76% suppression. This implies that incorporation of Chester or Navajo extracts into skin creams might be protective against skin cancer. Use of Arapaho or Choctaw extracts would probably have minimal effect.
A later effect in the carcinogenesis is angiogenesis leading to enhanced availability of nutrients for the developing tumor. Invasion of the tissue surrounding the transformed cells is required for metastasis. Both of these activities require the matrix metalloproteinase enzymes. Extracts from Arapaho and Chester, Meeker raspberry and muscadine grapes were all highly effective at inactivating these enzymes.
Tate, P., A. Kuzmar, S.W. Smith, D.E. Wedge, and L. Larcom: comparative Effects of Eight Varieties of Blackberry on Mutagenesis. Nutrition Research 23, 971-997, 2003.
Tate, P., J. God, R. Bibb, Q. Lu and L. Larcom: Inhibition of Metalloproteinase Activity in Fruit Extracts. Cancer Letters 212, 153-158, 2004.
Smith, S.H., P. Tate, G. Huang, J.B. Magee, K.M. Meepagala, D.E. Wedge and L. Larcom. Antimutagenic Activity of Berry Extracts. J. Medicinal Food, 7, 450-455, 2004.