cancer-prevention

Matcha/green tea has for many centuries been regarded as an essential part of good health in Japan and China. Many believe it can help reduce the risk of cancer, and a growing body of evidence backs this up.

Recent Research Papers on
cancer-prevention

Modulatory efficacy of Green tea polyphenols on glycoconjugates and immunological markers in 4-Nitroquinoline 1-oxide-induced oral carcinogenesis—A therapeutic approach

Author: Periasamy Srinivasan and Kuruvimalai Ekambaram Sabitha and Chennam Srinivasulu Shyamaladevi

Green tea polyphenols (GTP) has been used as a chemopreventive agent world wide against chemically induced cancer. The present study is aimed to understand the therapeutic action of GTP on glycoconjugates and immunological markers in 4-Nitroquinoline 1-oxide (4-NQO)-induced oral cancer over a period of 30 days at 200 mg/kg, p.o., Oral cancer was induced by painting 4-NQO for 8 weeks followed by administration of GTP after 22 weeks, for 30 days. Glycoconjugates such as hexose, hexosamine, sialicacid, fucose and mucoprotein were analysed. Expression of glycoconjugates was examined through histology and SDS-PAGE. Immunological markers such as circulating immune complex and mast cell density were studied. Oral cancer-induced animals showed a significant increase in levels of glycoconjugates and its expression, similar to that observed for immunological markers. Treatment with GTP altered the expression of glycoconjugates as well as immunological markers. The results suggest that GTP modulates both the expression of glycoconjugates and immunological markers resulting in regression of oral cancer.

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Green tea consumption improves plasma lipid profiles in adults

Author: Susana Coimbra and Alice Santos-Silva and Petronila Rocha-Pereira and Susana Rocha and Elisabeth Castro

Cardiovascular disease is the major cause of mortality and morbidity in the Western world. Green tea prepared with leaves of Camellia sinensis is particularly rich in antioxidants, which seem to have a crucial role in atherogenesis. The aim of our investigation was to evaluate the effect of green tea drinking on the lipid profile in 29 Portuguese subjects. The lipid profile included the measurement of total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol, triacylglycerols, apolipoprotein A-I, apolipoprotein B, and lipoprotein(a). The measurements were performed at the beginning of the study, and after 3 weeks of drinking 1 L of water, and after 4 weeks of drinking 1 L of green tea daily. Tea was prepared every day at the same conditions of temperature, time of infusion, and concentration. No dilution effect was observed after water drinking. After drinking green tea, a significant beneficial improvement in the lipid profile of subjects was observed. A decrease in cholesterol, low-density lipoprotein cholesterol, apolipoprotein B, and ratio of cholesterol/HDL-C, but an increase in HDL-C and apolipoprotein A-I, was observed in the subjects. No significant differences were observed for triacylglycerol and lipoprotein(a). Our data suggest that drinking green tea has a beneficial effect protecting against the risk for cardiovascular disease by improving blood lipid levels.

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Effects of green tea extracts on gene expression in HepG2 and Cal-27 cells

Author: Shin-Pei Yang and Kimberly Wilson and Abdul Kawa and Gregory M. Raner

Green tea extract is known to contain compounds that are able to produce antioxidant effects in many types of living cells. Treatment of cultured human hepatoma (HepG2) cells with green tea extract resulted in dramatically increased expression of at least 15 genes that are present on a commercial human drug metabolism gene array. RT-PCR was used to confirm the microarray results, and analysis of the 5′-flanking region of each of these genes revealed potential electrophile/antioxidant response elements. Members of the acetyl transferase, epoxide hydrolase, sulfotransferase and glutathione transferase gene families were strongly induced. In addition, the human tongue carcinoma cell line Cal-27 did not respond to green tea extract in the same way, as none of the induced genes in the HepG2 cells were induced in the Cal-27 cells. The lack of induction of detoxification enzymes in the Cal-27 cell line may help to explain the previously observed increased cytotoxicity of green tea catechins on this cell line.

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The effect of green tea in oxidative stress

Author: Susana Coimbra and Elisabeth Castro and Petronila Rocha-Pereira and Irene Rebelo and Susana Rocha and Alice Santos-Silva

Summary Background & aims Green tea, an infusion prepared with the leaves of Camellia sinensis is particularly rich in flavonoids, which are strong antioxidants. Tea drinking, by providing antioxidants, may become valuable in several oxidative stress conditions. Our aim was to evaluate the effect of green tea drinking on some factors reflecting the development of oxidative stress in plasma and in erythrocytes. Methods The study was performed in 34 Portuguese subjects. We evaluated the total antioxidant status (TAS), the lipid peroxidation products—malonyldialdehyde (MDA) and malonyldialdehyde+4-hydroxy-2(E)-nonenal (MDA+4-HNE)—and the oxidative changes in erythrocyte membrane, namely membrane bound haemoglobin (MBH) and the band 3 profile. Analytical evaluations were performed after 3 weeks drinking 1l of water daily, and after 4 weeks drinking 1l of green tea daily. Tea was prepared daily at the same conditions of temperature, time of infusion and concentration. Results After green tea drinking, we found a significant reduction in serum levels of MDA and MDA+4-HNE and in the oxidative stress within the erythrocyte, as suggested by a significantly lower value of MBH and by changes in band 3 profile towards a normal mean profile, namely an increase in the band 3 monomer. A rise in the antioxidant capacity was also observed. Conclusions Our data suggest for green tea drinking a beneficial effect, by reducing the development or the enhancement of oxidative stress and, therefore, protecting the individual for oxidative stress diseases. Moreover, we propose further studies about the value of band 3 profile and of MBH in providing a cumulative measurement of the effect of green tea drinking upon the oxidative stress in cells. Moreover, further studies are also needed, to clarify the effect of green tea consumption, the value of regular green tea consumption and the way it should be prepared to reach a healthy effect.

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Effects of iron, ascorbate, meat and casein on the antioxidant capacity of green tea under conditions of in vitro digestion

Author: Isidora Alexandropoulou and Michael Komaitis and Maria Kapsokefalou

The hypothesis that interactions of dietary polyphenols with dietary iron occur during digestion and result in a decrease of the post-absorptive antioxidant properties of polyphenols was investigated. The hypothesis was tested in vitro, under conditions that simulate gastrointestinal digestion. Mixtures of green tea, iron, and three dietary factors that modify the form of iron in the lumen, namely ascorbic acid, meat or casein, were subjected to an in vitro gastrointestinal digestion. Antioxidant capacity (FRAP assay), iron concentration (ferrozine assay) and polyphenol concentration (Folin–Ciocalteau assay) were measured in the in vitro digests. The presence of iron decreased the antioxidant capacity and the polyphenol concentration of green tea digests. The presence of ascorbic acid increased, while meat and casein decreased the antioxidant capacity of green tea. The factorial analysis of the data suggests that protein and iron interact with green tea polyphenols during the in vitro digestion and decrease their antioxidant capacity. These results support the aforementioned hypothesis.

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Combination of green tea, phytic acid, and inositol reduced the incidence of azoxymethane-induced colon tumors in Fisher 344 male rats

Author: J. Khatiwada and M. Verghese and L.T. Walker and L. Shackelford and C.B. Chawan and R. Sunkara

Epidemiological studies have shown an inverse relationship between consumption of nutritive/non-nutritive foods of plant origin and colon cancer incidence. This study was conducted to determine the effect of green tea, phytic acid, and inositol at 2 g/100 ml levels singly and in combination on azoxymethane (AOM) induced colon tumors in Fisher 344 male rats. After an acclimatization period of one week, 8 groups of rats (15 rats each) were initially assigned to consume AIN 93G and later AIN 93M diet. All treatments were given in drinking water. All the rats received 16 mg/kg body mass AOM, two s/c injections at seven and eight week of age. Rats were killed at 46 week of age by CO2 euthanasia. Tumor incidence (percent) and tumors per tumor-bearing rat (TBR) in the control were significantly higher ( $P < 0.05$ ) than all treatment groups. Glutathione-S-transferase (GST) activity was significantly higher in treatment groups compared to control. These findings suggest that the additive effect of green tea, phytic acid and inositol may reduce the incidence of colon tumors, and can also be used as an adjuvant to chemomodulation.

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Clinical effects of oral green tea extracts in four patients with low grade B-cell malignancies

Author: T.D. Shanafelt and Y.K. Lee and T.G. Call and G.S. Nowakowski and D. Dingli and C.S. Zent and N.E. Kay

Green tea or its constituents have long been touted as a health promoting substance including claims it may have cancer prevention properties. We previously reported the in vitro ability of one tea polyphenol, epigallocatechin gallate (EGCG), to induce apoptotic cell death in the leukemic B-cells from a majority of patients with chronic lymphocytic leukemia (CLL). After the publication of our findings many patients with CLL and other low grade lymphomas began using over-the-counter products containing tea polyphenols despite the absence of evidence to suggest clinical benefit, definition of possible toxicities, or information on optimal dose and schedule. We have become aware of four patients with low grade B-cell malignancies seen in our clinical practice at Mayo Clinic who began, on their own initiative, oral ingestion of EGCG containing products and subsequently appeared to have an objective clinical response. Three of these four patients met criteria for partial response (PR) by standard response criteria. Although spontaneous remission/regression is occasionally observed in individuals with low grade B-cell malignancies, such events are rare. Several patients presented here had documented steady clinical, laboratory, and/or radiographic evidence of progression immediately prior to initiation of over-the-counter green tea products and then developed objective responses shortly after self-initiating this therapy. Such anecdotes highlight the need for clinical trials of tea polyphenols to define the optimal dosing, schedule, toxicities, and clinical efficacy before widespread use can be recommended. An NCI sponsored phase I/II trial of de-caffeinated green tea extracts for patients with asymptomatic, early stage CLL opened at Mayo Clinic in August 2005.

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Epigallocatechin-3-gallate (EGCG): Chemical and biomedical perspectives

Author: Dale G. Nagle and Daneel Ferreira and Yu-Dong Zhou

The compound (−)-epigallocatechin-3-gallate (EGCG) is the major catechin found in green tea [Camellia sinensis L. Ktze. (Theaceae)]. This polyphenolic compound and several related catechins are believed to be responsible for the health benefits associated with the consumption of green tea. The potential health benefits ascribed to green tea and EGCG include antioxidant effects, cancer chemoprevention, improving cardiovascular health, enhancing weight loss, protecting the skin from the damage caused by ionizing radiation, and others. The compound EGCG has been shown to regulate dozens of disease-specific molecular targets. Many of these molecular targets are only affected by concentrations of EGCG that are far above the levels achieved by either drinking green tea or consuming moderate doses of green tea extract-based dietary supplements. In spite of this, well-designed double-blinded controlled clinical studies have recently demonstrated the efficacy of green tea extracts and purified EGCG products in patients. Therefore, this review highlights results from what the authors believe to be some of the most clinically significant recent studies and describes current developments in the stereoselective total synthesis of EGCG.

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Green tea and its polyphenolic catechins: Medicinal uses in cancer and noncancer applications

Author: Nurulain T. Zaveri

Can drinking several cups of green tea a day keep the doctor away? This certainly seems so, given the popularity of this practice in East Asian culture and the increased interest in green tea in the Western world. Several epidemiological studies have shown beneficial effects of green tea in cancer, cardiovascular, and neurological diseases. The health benefits associated with green tea consumption have also been corroborated in animal studies of cancer chemoprevention, hypercholesterolemia, artherosclerosis, Parkinson's disease, Alzheimer's disease, and other aging-related disorders. However, the use of green tea as a cancer chemopreventive or for other health benefits has been confounded by the low oral bioavailability of its active polyphenolic catechins, particularly epigallocatechin-3-gallate (EGCG), the most active catechin. This review summarizes the purported beneficial effects of green tea and EGCG in various animal models of human diseases. Dose-related differences in the effects of EGCG in cancer versus neurodegenerative and cardiovascular diseases, as well as discrepancies between doses used in in vitro studies and achievable plasma understanding of the in vivo effects of green tea catechins in humans, before the use of green tea is widely adopted as health-promoting measure.

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Apoptosis induction by green tea compounds in cervical cancer cells