cancer-prevention

Author: Hirota Fujiki and Masami Suganuma and Sachiko Okabe and Eisaburo Sueoka and Naoko Sueoka and Nobukazu Fujimoto and Yuri Goto and Satoru Matsuyama and Kazue Imai and Kei Nakachi 

The study of green tea polyphenols as cancer preventives is approaching a new era, with significant results accumulating rapidly. This paper briefly reviews four topics related to mechanisms of action of tea polyphenols: (I) identification of the genes commonly affected by EGCG, as demonstrated by Clontech’s Atlas™ cDNA Expression Array; (II) the significance of heterogenous nuclear ribonucleoprotein B1 (hnRNP B1) as a new biomarker for early detection of lung cancer, and inhibition of its expression by EGCG; (III) the synergistic or additive effects of EGCG with the cancer preventive agents, sulindac and tamoxifen, on induction of apoptosis in PC-9 cells and on inhibition of intestinal tumor development in multiple intestinal neoplasia (Min) mice; (IV) the results of a 10 year prospective cohort study demonstrating the effectiveness of daily consumption of green tea in preventing cancer, and a prototype study for developing green tea beverage as cancer preventive.

Get the whole article here

Author: Masao Hirose and Toru Hoshiya and Yasumoto Mizoguchi and Atsushi Nakamura and Keisuke Akagi and Tomoyuki Shirai

Modifying effects of green tea catechins (GTCs) on the post-initiation stage of colon, lung and thyroid carcinogenesis were examined in F344 male rats. Groups of 20 animals were given subcutaneous injections of 40 mg/kg body wt of 1,2-dimethylhydrazine twice a week for 2 weeks or oral administration of 0.1% 2,2′-dihydroxy-di-n-propylnitrosamine (DHPN) in the drinking water for 2 weeks for initiation. They then received diet containing 1 or 0.1% green tea catechin or basal diet alone for 33 weeks. Histopathological examination after final sacrifice showed that although total incidence and multiplicity of colon tumors were not significantly different from controls, values for colon adenomas were decreased while those for carcinomas and the average size of tumors were significantly increased in the 0.1% GTC group. A similar tendency was observed for the 1% GTC group. Incidences and/or multiplicity of lung hyperplasia and tumors, and thyroid lesions did not significantly vary among the DHPN-treated groups. These results indicate that GTCs do not inhibit, but rather may enhance colon carcinogenesis, while not influencing lung and thyroid carcinogenesis under the present experimental conditions.

Get the whole article here

Author: Santosh K Katiyar and Bethany M Bergamo and Praveen K Vyalil and Craig A Elmets

Green tea is a popular beverage consumed worldwide. The epicatechin derivatives, which are commonly called ‘polyphenols’, are the active ingredients in green tea and possess antioxidant, anti-inflammatory and anti-carcinogenic properties. Studies conducted by our group on human skin have demonstrated that green tea polyphenols (GTP) prevent ultraviolet (UV)-B-induced cyclobutane pyrimidine dimers (CPD), which are considered to be mediators of UVB-induced immune suppression and skin cancer induction. GTP treated human skin prevented penetration of UV radiation, which was demonstrated by the absence of immunostaining for CPD in the reticular dermis. The topical application of GTP or its most potent chemopreventive constituent (−)-epigallocatechin-3-gallate (EGCG) prior to exposure to UVB protects against UVB-induced local as well as systemic immune suppression in laboratory animals. Additionally, studies have shown that EGCG treatment of mouse skin inhibits UVB-induced infiltration of CD11b+ cells. CD11b is a cell surface marker for activated macrophages and neutrophils, which are associated with induction of UVB-induced suppression of contact hypersensitivity responses. EGCG treatment also results in reduction of the UVB-induced immunoregulatory cytokine interleukin (IL)-10 in skin as well as in draining lymph nodes, and an elevated amount of IL-12 in draining lymph nodes. These in vivo observations suggest that GTPs are photoprotective, and can be used as pharmacological agents for the prevention of solar UVB light-induced skin disorders associated with immune suppression and DNA damage.

Get the whole article here

Author: Gilberto Santana-Rios and Gayle A. Orner and Adams Amantana and Cynthia Provost and Shiau-Yin Wu and Roderick H. Dashwood

There is growing interest in the potential health benefits of tea, including the antimutagenic properties. Four varieties of white tea, which represent the least processed form of tea, were shown to have marked antimutagenic activity in the Salmonella assay, particularly in the presence of S9. The most active of these teas, Exotica China white tea, was significantly more effective than Premium green tea (Dragonwell special grade) against 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and four other heterocyclic amine mutagens, namely 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethyl-3H-imidazo[4,5-f]quinoxaline (4,8-DiMeIQx), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2). Mechanism studies were performed using rat liver S9 in assays for methoxyresorufin O-demethylase (MROD), a marker for the enzyme cytochrome P4501A2 that activates heterocyclic amines, as well as Salmonella assays with the direct-acting mutagen 2-hydroxyamino-3-methylimidazo[4,5-f]quinoline (N-hydroxy-IQ). White tea at low concentrations in the assay inhibited MROD activity, and attenuated the mutagenic activity of N-hydroxy-IQ in the absence of S9. Nine of the major constituents found in green tea also were detected in white tea, including high levels of epigallocatechin-3-gallate (EGCG) and several other polyphenols. When these major constituents were mixed to produce ‘artificial’ teas, according to their relative levels in white and green teas, the complete tea exhibited higher antimutagenic potency compared with the corresponding artificial tea. The results suggest that the greater inhibitory potency of white versus green tea in the Salmonella assay might be related to the relative levels of the nine major constituents, perhaps acting synergistically with other (minor) constituents, to inhibit mutagen activation as well as ‘scavenging’ the reactive intermediate(s).

Get the whole article here

Author: C.W. Embola and O.S. Sohn and E.S. Fiala and J.H. Weisburger

Tea is one of the most frequently consumed beverages in the world, second only to water. Epidemiological studies have associated the consumption of green tea with a lower risk of several types of cancers, including stomach, oral cavity, esophagus, and lung. This paper deals with the mechanism of action of tea as an effective chemopreventive agent for toxic chemicals and especially carcinogens. UDP-glucuronosyltransferase (UDP-GT) activities towards p-nitrophenol were markedly increased (51.8% or 1.5-fold) in rats that consumed tea compared with the control animals on water. Induction of UDP-glucuronosyltransferase activity by tea may involve the UDP-GT1 (UGT1A) gene complex of the UDP-GT multigene family. Therefore, a major mechanism of tea as a chemopreventive agent is induction of the microsomal detoxification enzyme, UDP-glucuronosyltransferase.

Get the whole article here

Author: E.I Korotkova and Y.A Karbainov and A.V Shevchuk

A highly attractive, convenient and especially sensitive voltammetric approach for the study of antioxidant properties and determination of their activity is suggested in this work, where antioxidants are substances, which interrupt radical-chain oxidation processes in organic and inorganic molecules. The comparative analysis of the activity of well-known antioxidants such as ascorbic and citric acids, glucose, their compound solutions, some food products (green tea extract, apple vinegar) and pharmaceuticals (haemodesum, polyglucinum, Ringer solution) has been carried out. The character of the antioxidant influence on the oxygen electrochemical reduction has been investigated. Finally the use of these substances for prophylactic purposes has been recommended.

Get the whole article here

Author: Borhane Annabi and Marie-Paule Lachambre and Nathalie Bousquet-Gagnon and Martine Pagé and Denis Gingras and Richard Béliveau

Author: Hirota Fujiki and Masami Suganuma and Kazue Imai and Kei Nakachi

Green tea and (−)-epigallocatechin gallate (EGCG) are now acknowledged cancer preventives in Japan and has made it possible for us to establish the concept of a cancer preventive beverage. For the general population, we recommend 10 cups of green tea daily supplemented with green tea tablets. For cancer patients following treatment, we here present new evidence that green tea and a cancer preventive drug, sulindac, have synergistic preventive effects. An approach to develop green tea capsules as a cancer preventive drug in the US is discussed, aiming at taking full advantage of this cancer preventive beverage.

Get the whole article here

Author: Masao Hirose and Tsuyoshi Yamaguchi and Yasumoto Mizoguchi and Keisuke Akagi and Mitsuru Futakuchi and Tomoyuki Shirai

Differences in the modifying effects of green tea catechins (GTC) on intestinal carcinogenesis by different formulations, doses and administration routes were investigated in male rats pretreated with 1,2-dimethylhydrazine (DMH). One hundred and eighty nine F344 male rats received subcutaneous injections of DMH at 40 mg/kg body weight twice a week for 3 weeks. Three days after completion of the carcinogen treatment, they were divided into nine groups. Each was administered a different source of 0.1% or 0.01% of GTC (Mitsui Norin Co. (M) or Taiyo Kagaku Co. (T)) either in the diet (D) or the drinking water (W), or basal diet and tap water alone without GTC for 33 weeks and then killed for autopsy. The survival rate tended to be lower with 0.01% MGTC (W) group than in the other groups. In the large intestine, although the multiplicity and/or incidences of adenomas showed tendencies for dose-dependent decrease in all GTC groups, and the average volumes of tumors tended to be decrease dose-dependently in the MGTC (W) and TGTC (W) groups, the multiplicity of carcinomas did not show such a trend, rather being significantly increased in the 0.01% MGTC (D) and 0.1% TGTC (W) groups. In the small intestine, the incidence and the multiplicity of tumors in all GTC treated groups had a tendency to decrease. On the other hand, the volume of tumors was increased with statistical significance in the 0.01% MGTC (W) and 0.1% TGTC (W) groups. Thus it can be concluded that GTC does not exert chemopreventive effects on intestinal carcinogenesis irrespective of its formulation, dose or route of administration.

Get the whole article here

Author: Helaine M Alessio and Ann E Hagerman and Mary Romanello and Stephane Carando and Melinda S Threlkeld and J Rogers and Yoana Dimitrova and Subiquah Muhammed and Ronald L Wiley

The effects of green tea on biomarkers of exercise-induced oxidative status were measured in young male Sprague-Dawley rats. Rats (n = 12) drank green tea or water ad lib for 6.5 weeks. Half of each group was sacrificed at rest, and the other half ran 25 m/min at 0% grade for approximately 30 min immediately before sacrifice. Green tea had no effect on resting heart rate, blood pressure, body weight, cholesterol, or triglycerides. Tea consumption had a mild influence on total plasma antioxidants, heart glutathione, and plasma ascorbic acid. Exercise had a major impact on malonaldehyde (MDA) equivalents in kidney (+290%, p = 0.0001), and to a lesser extent, liver (+81%, p = 0.18) in rats that drank water. In contrast, kidney MDA equivalents were unchanged by exercise in rats that drank green tea. Green tea may have selective protective effects within the body, especially on the kidney.

Get the whole article here