Cancer prevention by tea: animal studies, molecular mechanisms and human relevance

Abstract

Extracts of tea, especially green tea, and tea polyphenols have been shown to inhibit the formation and development of tumours at different organ sites in animal models. There is considerable evidence that tea polyphenols, in particular (−)-epigallocatechin-3-gallate, inhibit enzyme activities and signal transduction pathways, resulting in the suppression of cell proliferation and enhancement of apoptosis, as well as the inhibition of cell invasion, angiogenesis and metastasis. Here, we review these biological activities and existing data relating tea consumption to human cancer risk in an attempt to understand the potential use of tea for cancer prevention.Dietary factors can substantially influence human cancer risk. Many food items, beverages and dietary constituents have reported cancer-preventive or anticancer activities. Tea, a commonly consumed beverage derived from the dried leaves of the Camellia sinensis plant, has been studied extensively for its health benefits, including cancer prevention. These studies are important because tea is consumed by a large proportion of the world's population and is the most popular beverage after water. Therefore, tea is the major source of dietary flavonoids (or polyphenols) in many populations. Tea is a unique food item in that the major constituents, especially those in green tea, are well characterized, allowing their biological activities to be thoroughly studied. The relationship between tea consumption and human cancer can be investigated using retrospective and prospective studies in which tea consumption is assessed by dietary recalls or by specific urinary markers.Although different aspects of tea and cancer prevention have been covered by previous reviews [1][2][3][4][5][6][7][8][9][10] , this Review critically assesses existing data and discusses our current understanding of how tea constituents might prevent cancer. We use selected recent findings to illustrate the types of laboratory results that are available. We also briefly review the results of human epidemiological and intervention studies, interpret these results on the basis of our understanding of the biochemical properties of tea constituents (BOX 1) and discuss possible mechanisms by which tea polyphenols prevent cancer development. Finally, we discuss the opportunities and challenges presented by the study of tea for cancer prevention. We hope that this Review will have wide-ranging implications, as many of the issues discussed here might also be applicable to studies of other dietary materials.Correspondence to: Chung S. Yang, csyang@rci.rutgers.edu. NIH Public Access Author ManuscriptNat Rev Cancer. Author manuscript; available in PMC 2010 March 1. Tea constituents and their biochemical propertiesThe major catechins (a group of polyphenols) in green tea are (−)-epigallocatechin-3-gallate (EGCG), (−)-epigallocatechin (EGC), (−)-epicatechin-3-gallate (ECG) and (−)-epicatechin (BOX 1). Tea catechins are characterized by the dihydroxyl or trihydroxyl substitutions on the B ring and the m-...

Preventive Effects of (−)-Epigallocatechin Gallate on Diethylnitrosamine-Induced Liver Tumorigenesis in Obese and Diabetic C57BL/KsJ-db/db Mice

“…Green tea, a beverage commonly consumed worldwide, possesses anticancer and cancer chemopreventive properties, and (À)-epigallocatechin gallate (EGCG) is the most potent of the green tea catechins (GTC) with respect to exerting these beneficial effects (9,10). EGCG inhibits cell proliferation and induces apoptosis in cancer cells by inhibiting activation of some types of receptor tyrosine kinases (RTK) and related downstream signaling pathways (11,12).…”

A green chemical approach for synthesis of shape anisotropic gold nanoparticles

“…Figure 1a-c depicts the chemical structures of Fig. 1d is that of a typical thearubigin possessing the carboxylic acid (COOH) functional group, well known for their capping abilities [18,23]. Therefore, the tea extract performs the dual role of novel reducing agent as well as an efficient bio-surfactant.…”

“…Many plants or plant products have been employed for the synthesis of Au NPs, some of which include, Emblica officinalis, Acacia nilotica (Babool), alfalfa biomass, geranium, Azadirachta indica leaves, gum kondagogu, gram-beans and tea leaves [10][11][12][13][14][15][16][17]. Camellia sinensis commonly known as tea is a rich source of polyphenolic compounds, which exhibits a variety of health benefits such as protection against heart diseases, cancer and the paralytic actions of botulinum neurotoxins [18,19]. These attractive health benefits apart from its complete green approach have turned tea extract as an important species for synthesis of NPs.…”

Growth inhibition of Walker carcinosarcoma 256 with alcoholic extract of green tea leaves (Camellia sinensis)

“…In a study evaluating the toxicity of different concentrations (0.3%, 1.25%, 5%) of catechins in male rats, the weight of the thymus, lungs, heart, spleen, liver, thyroid gland and pituitary gland was significantly reduced in animals treated with the highest concentration of catechins 16 . In contrast, in our experiment the average weight of the spleen, liver and kidneys was similar for rats in the treatment groups (alcoholic extract of leaves of C. Sinensis at 0.07 g/Kg and 0.14 g/Kg) and rats in the negative control group.…”