The tomato-derived carotenoid lycopene may reduce risk of cancer by activating special cancer preventive enzymes, according to a new lab study by an Israeli team. The researchers incubated breast and liver cancer cells with lycopene and found that natural chemical stimulated production of phase II detoxification enzymes, which remove harmful carcinogens from the cells and the body.
As expression of phase II enzymes is regulated by the ‘antioxidant response element' (ARE), the new research suggests that this could be the mechanism behind the cancer-preventive effect of tomatoes, said Dr Joseph Levy and colleagues from Ben-Gurion University of the Negev, Beer-Sheva, Israel, speaking at the American Association for Cancer Research annual meeting this week.
A number of epidemiological studies have found that as the consumption of tomato products increases, risk of certain types of cancer decreases. It has been proposed that this could be due to a number of different compounds in tomatoes, rather than lycopene alone.
However tests on other carotenoids did not reveal the same effect. Beta-carotene had a lesser effect, while asataxanthin and another tomato carotenoid called phytoene had no impact on the cancer cells. "The transactivation was dose-dependent and unexpectedly specific for lycopene, since astaxanthin, beta-carotene and phytoene had no effect. This specificity suggests that activation of ARE-mediated transcription by carotenoids is not related solely to their antioxidant properties," noted the researchers.
Their findings support a unique mechanism for the cancer-preventive action of lycopene. A meta-analysis of 21 studies in this month's Cancer Epidemiology Biomarkers and Prevention (2004, vol.13, 340-345), concluded that high amounts of tomato-based products may significantly reduce the risk of prostate cancer but noted that further research is needed to determine the type and quantity of tomato products and their role in preventing prostate cancer. Lycopene has also been linked to reduced risk of heart disease.
Back to top of document