Topics: Cancer, Signal transduction, Gene expression Pages: 47 (12860 words) Published: August 31, 2011

Young-Joon Surh
Chemoprevention refers to the use of agents to inhibit, reverse or retard tumorigenesis. Numerous phytochemicals derived from edible plants have been reported to interfere with a specific stage of the carcinogenic process. Many mechanisms have been shown to account for the anticarcinogenic actions of dietary constituents, but attention has recently been focused on intracellular-signalling cascades as common molecular targets for various chemopreventive phytochemicals. Cancer is a growing health problem around the world — particularly with the steady rise in life expectancy, increasing urbanization and the subsequent changes in environmental conditions, including lifestyle. According to a recent report by the World Health Organization (WHO), there are now more than 10 million cases of cancer per year worldwide. In 2003, it is estimated that approximately 1,300,000 new cases of cancer will be diagnosed, and more than 550,000 people will die from cancer in the United States alone. Although there is no ‘magic bullet’ that can completely conquer cancer, many types of the disease might be avoidable. Cancer risk can be reduced by eliminating the identified carcinogens — or at least minimizing exposure to them — but, without complete identification of the corresponding risk factors, such primary prevention might be difficult to implement. Furthermore, the avoidance of some risk factors could require large lifestyle changes, which are not easy to implement. It has been estimated that more than two-thirds of human cancers could be prevented through appropriate lifestyle modification. Richard Doll and Richard Peto have reported that 10–70% (average 35%) of human cancer mortality is attributable to diet1. Their observations, which are based on statistical and epidemiological data, mainly concerned dietary factors that increase risk. Although the exact percentage is uncertain, there are several lines of compelling evidence from epidemiological, clinical and laboratory studies that link cancer risk to the nutritional factors. A wide array of substances derived from the diet have been found to stimulate the development, growth and spread of tumours in experimental animals, and to transform normal cells into malignant ones. These are regarded as suspected human carcinogens. So, many dietary constituents can increase the risk of developing cancer, but there is also accumulating evidence from population as well as laboratory studies to support an inverse relationship between regular consumption of fruit and vegetables and the risk of specific cancers. Several organizations — such as the WHO, the American Cancer Society, the American Institute of Cancer Research (AICR) and the National Cancer Institute (NCI) — have established dietary guidelines to help people reduce the cancer risk (for further information, see the 1997 World Cancer Research Fund and AICR report in online links box). Many clinical trials on the use of nutritional supplements and modified diets to prevent cancer are ongoing. It is conceivable that in the future people might only need to take specially formulated pills that contain substances derived from edible plants to prevent cancer or delay its onset2. However, a precise assessment of the mechanisms by which the components of fruit and vegetables prevent cancer is necessary before they can be recommended for inclusion in dietary supplements or before they can be tested in human intervention trials. Phytochemicals are non-nutritive components in the plant-based diet (‘phyto’ is from the Greek word meaning plant) that possess substantial anticarcinogenic and antimutagenic properties. Given the great structural

College of Pharmacy, Seoul National University, Shinlim-dong, Kwanak-ku, Seoul 151-742, South Korea. e-mail: doi:10.1038/nrc1189



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