Background
Numerous studies have found that regular, moderate use of alcohol affects the levels of important female hormones, especially for postmenopausal women whose bodies make much less estrogen and progesterone than before they entered menopause. As a consequence, women's breast cells are exposed to higher levels of estrogen if alcohol was consumed. This may in turn trigger the cells, which are estrogen sensitive in such women, to become cancerous.
Phenolic phytochemicals are widely distributed in the plant kingdom. In various experiments, it has been shown that selected polyphenols, mainly flavonoids, confer protective effects on the cardiovascular system and have anticancer, antiviral and antiallergic properties. Flavonoids are low molecular weight compounds composed of a three-ring structure with various substitutions, which appear to be responsible for the antioxidant and antiproliferative properties. It is well known that consumption of red wine in moderation is associated with reduced risk of cardiovascular disease. Many believe that the low incidence of coronary artery disease found among the French could be partially related to the pharmacological properties of polyphenolic compounds present in red wine.
A New Study
Three researchers from the Universidade do Porto, Portugal set out to examine whether phenolic compounds could have properties that would be effective in fighting breast cancer, the most commonly diagnosed nondermatologic cancer and the second leading cause of cancer-related deaths among women in the United States. They investigated the effect of three phenolic compounds -- epigallocatechin gallate (EGCG), xanthohumol (XN) and resveratrol (RES) -- substances present in significant concentrations in tea, beer and red wine, respectively, on the growth of a human breast cancer cell line, MCF-7.
The authors of the study entitled "Phenolic Compounds in the Control of Breast Cancer Cell Growth" are S. Pinheiro-Silva, I. Azevedo, and C. Calhau, all at the Universidade do Porto, Porto, Portugal. They will present their findings at the American Physiological Society's (APS) (www.the-aps.org) annual scientific conference, Experimental Biology 2003, being held April 17-21, 2004, at the Washington, D.C. Convention Center.
Methodology
The cell line (MCF-7) was cultured in appropriate medium, in different cell plates, under control conditions or in the presence of any of the three polyphenols: EGCG, XN or RES. Various concentrations and various time periods of treatment were tested for each compound. At the chosen time points, the cells were taken off the plates and counted in a Neubauer chamber after exposure to tryptan blue (0.4 percent). The colorant is excluded from live cells, and so the method allows simultaneously quantifying the number of cells (index of proliferation) and cytotoxicity (ratio between dead and live cells). In other experiments, 3H-thymidine incorporation was evaluated in each time and treatment condition, indicating the effect of treatment on DNA synthesis.
Results
All three polyphenolic compounds tested showed a significant effect, decreasing breast cancer cells proliferation. The effects were observed both over the number of cells after each time period, and over 3H-thymidine incorporation. Cytotoxicity depended on the compound concentration and duration of treatment.
XN, found in beer, was the most potent polyphenol over breast cancer cell growth: it showed its effect more rapidly and at a lower concentration (24 hours, one to 10 μM). On the other hand, cytotoxicity was observed only at 50 to 100 μM concentrations, and usually after longer time periods. XN IC50 for 3H-thymidine incorporation, at 24 h of treatment, was found to be 18.3 μM.
RES did also show an anti-proliferative effect over the growth of the breast cancer cell line, albeit with less potency than XN: at 24 hours, treatment anti-proliferative effect was significant only for the higher tested concentrations, 50 and 100 μM.
On the other hand, the effects of RES over 3H-thymidine incorporation were not in linear correlation with the effects over cell number, indicating that it is probably acting on more than one biochemical event. Its IC50 for 3H-thymidine incorporation decrease, at 24 hours treatment, was found to be 71.2 μM.
EGCG showed an inhibitory effect upon cell growth, but was less potent than XN and RES. Only at the highest concentration tested, 100 μM, the proliferative inhibitory effect was statistically significant after 24 hours of treatment. At 50 μM, the inhibitory effect was significant only after 72 hours exposure. On the other hand, EGCG showed no cytotoxicity.
Conclusions
The researchers concluded the following:
- three polyphenolic compounds, EGCG, XN and RES, known to be abundant in tea, beer and red wine, respectively, when present in the nutritive medium of a breast cancer cell line (MCF-7), were all able to reduce cell proliferation. These effects could be observed at concentrations that were not cytotoxic.
- a decrease in 3H-thymidine incorporation, a commonly used index of DNA synthesis, was also observed in the presence of the compounds, very much in correspondence with the anti-proliferative effect in the case of XN. EGCG, in this selection of polyphenols, was the least potent on a weight basis, although that may have no therapeutic meaning since it was also the least toxic compound (i.e. it can be given in higher doses).
- these biochemical results, over breast cancer cells, add support and meaning to epidemiological studies that relate consumption of certain beverages with a lesser incidence and prevalence of cancer.
This study does not call for women to increase alcohol consumption as a means of breast cancer prevention. The authors state that their findings suggest that further studies, namely in vivo studies, are necessary to fully support the inclusion of these compounds and/or beverages in diet recommendations in the perspective of cancer prevention.
The American Physiological Society (APS) is America's oldest biomedical sciences research society. The not-for-profit society, with some 11,000 members, is the publisher of 14 scientific journals, including the American Journal of Physiology, which has been published since 1898.
Editors Note: For further information or to schedule an interview with a member of the research team, please contact Donna Krupa at 703.967.2751 (cell), 703.527.7357 (office) or at djkrupa1@aol.com. Or contact the APS newsroom at 202.249.4009 between 9:00 AM and 6:00 PM EDT April 17-21, 2004.