茶多酚抗肿瘤效应机制研究进展

茶叶具有清头目,除烦渴,化痰,消食,利尿,解毒功能,可治疗头痛、目昏、多睡善寐、心烦口渴、食积痰滞、疟、痢等病证。茶叶的主要活性成分为茶多酚。现代研究表明,茶多酚除有抗衰老、预防心脑血管疾病外,还具有细胞毒作用、诱导肿瘤细胞凋亡与分化、抗畸变、抗癌症转移等综合效应。据此可以认为,茶多酚在抗肿瘤方面具有广阔的应用前景与深入研究的价值。     

Green Tea Drinking Habits and Esophageal Cancer in Southern China: A Case- Control Study

Aim: To investigate effects of green tea drinking and its temperature on esophageal cancer development.Methods: A 1:2 matched hospital-based case-control study including 150 cases and 300 controls was conducted insouthern area of China from June 2004 to May 2010. A self-designed questionnaire was used to collect informationon possible risk factors of esophageal cancer, and to assess the tea drinking habit and temperature. Conditionallogistic regression was used to calculate odds ratios (ORs) and corresponding 95% confidence intervals (CIs).Results: We find a significant protective effect of high consumption of green tea on esophageal cancer with lowtemperature tea (OR=0.79, 95%CI=0.29-0.97). However, drinking tea at a temperature of 70-79℃ and above 80℃was related to greatly elevated risk of esophageal cancer with ORs of 2.21 (1.57-5.53) and 4.74 (2.67-10.51). Anagreement was found between reported tea temperature and measured temperature (correlation coefficient =0.62).Further analysis indicated hot tea temperature to be associated with heavy risk of esophageal cancer in formerand current smokers and current drinkers (former and current smokers: OR=8.91(1.91-16.77) and 7.33(2.23-12.46), respectively; former and current drinkers: OR=7.58(0.83-9.53) and 6.93(2.01-10.65)). Conclusion: Inthe South China context, drinking tea at high temperature significantly increases risk of esophageal cancer,especially in drinkers and smokers.     

Green tea, black tea consumption and risk of lung cancer: A meta-analysis

Studies investigating the association of green tea and black tea consumption with lung cancer risk have reported inconsistent findings. To provide a quantitative assessment of this association, we conducted a meta-analysis on the topic. Studies were identified by a literature search in PubMed from 1966 to November 2008 and by searching the reference lists of relevant studies. Summary relative risk (RR) estimates and their corresponding 95% confidence intervals (CIs) were calculated based on random-effects model. Our meta-analysis included 22 studies provided data on consumption of green tea or black tea, or both related to lung cancer risk. For green tea, the summary RR indicated a borderline significant association between highest green tea consumption and reduced risk of lung cancer (RR = 0.78, 95% CI = 0.61–1.00). Furthermore, an increase in green tea consumption of two cups/day was associated with an 18% decreased risk of developing lung cancer (RR = 0.82, 95% CI = 0.71–0.96). For black tea, no statistically significant association was observe through the meta-analysis (highest versus non/lowest, RR = 0.86, 95% CI = 0.70–1.05; an increment of two cups/day, RR = 0.82, 95% CI = 0.65–1.03). In conclusion, our data suggest that high or an increase in consumption of green tea but not black tea may be related to the reduction of lung cancer risk.     

Inhibitory Effects of Tea Catechins, Black Tea Extract and Oolong Tea Extract on Hepatocarcinogenesis in Rat

Inhibitory effects of individual tea catechins ((-)-epicatechin, (-)-epigallocatechm, (-)-epicatechin gallate, (-)-epigallocatechin gallate), black tea extract and oolong tea extract on hepatocarcinogenesis were investigated. Male F344 rats received a single dose of diethylnitrosamine (200 mg/kg, i.p.), and thereafter phenobarbital (0.05%) was administered in the drinking water for a period of 6 weeks. Tea catechins, black tea extract or oolong tea extract were given during the entire experimental period, during only the initiation period or during only the promotion period. All four tea catechins, black tea extract and oolong tea extract (0.05 or 0.1%) significantly decreased the number and area of preneoplastic glutathione S -transferase placental form-positive foci in the liver. These results suggest that tea catechins, black tea extract and oolong tea extract have a chemopreventive action against hepatocarcinogenesis.     

茶绿色素的致突变作用研究

对中国绿茶提取物茶绿色素的致突变作用进行了研究。结果表明：茶绿色素８００（１／１６ＬＤ５０）ｍｇ／ｋｇ、１６００（１／８ＬＤ５０）ｍｇ／ｋｇ和３２００（１／４ＬＤ５０）ｍｇ／ｋｇ各剂量组小鼠骨髓ＰＣＥ微核率分别为３．６‰,３．２‰,２．６‰,与阴性对照组（２．８‰）比较均无显著性差异;３１２．５μｇ／ｌ皿、１２５０μｇ／皿、５０００μｇ／皿各剂量组ＴＡ９７、ＴＡ９８、ＴＡ１００、ＴＡ１０２等测试菌     

Green tea drinking habits and gastric cancer in southwest China

Aim: The purpose of this study was to investigate relationships between green tea consumption and gastric cancer development. Methods: A population-based case-control study including 200 cases and 200 controls was conducted in the southwest area of China from May 2010 to February 2011. A self-designed questionnaire was used to collect data on factors influencing gastric cancer development, including tea drinking, conditional logistic regression being used to calculate odds ratios (ORs) and corresponding 95% confidence intervals (95% CIs). Results: Cases with higher economic status had a reduced risk of gastric cancer, while those with cancer family history, drinking and smoking showed increased risk. Hot and very hot tea temperature was significantly related to high risk of gastric cancer with ORs (95%Cl) of 1.82 (1.03-3.52) and 3.07 (1.78-7.36), respectively. Further analysis indicated elevated risk of gastric cancer in former drinkers, former smokers and current drinkers when the measured tea temperature was hot. Conclusion: Drinking tea at high temperature increases the gastric cancer risk, especially in drinkers and smokers.     

Inhibitory Activity of Green and Black Tea in a Free Radical-generating System Using 2-Amino-3-methylimidazo[4,5-f]quinoline as Substrate

Green tea and black tea inhibit colon carcinogenesis in rats exposed to the cooked meat mutagen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). In the present investigation, green tea, black tea and (-)-epigallocatechin gallate (EGCG) were shown to block the production of oxygen free radicals derived from IQ in the presence of NADPH-cytochrome P450 reductase. In kinetic studies using IQ as tbe substrate and DMPO as a free radical spin trap, EGCG increased the Km of the reaction without altering Vmax, suggesting competitive enzyme inhibition (Ki=9.% mUM). This was confirmed in spectrophotometric studies using cytochrome c as the substrate, in which EGCG acted as a competitive inhibitor of NADPH-cytochrome P450 reductase (Ki=9.7 μM). These results suggest that the inhibitory activities of green tea and black tea in electron spin resonance assays using IQ as the substrate for the rednctase are related to an indirect effect on the enzyme rather than via direct scavenging of the free radicals. The possible implications of these findings are discussed in the context of pathways involved in the activation and detoxification of IQ in the colon.     

Tea consumption and breast cancer risk in a cohort of women with family history of breast cancer

Laboratory studies have observed chemopreventive effects of black and green tea on breast cancer development, but few epidemiologic studies have identified such effects. We investigated the association between tea consumption and breast cancer risk using data from 45,744 U.S. and Puerto Rican women participating in the Sister Study. Frequency and serving size of black and green tea consumption were measured at cohort enrollment. Breast cancer diagnoses were reported during follow-up and confirmed by medical record review. Multivariable Cox proportional hazards regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI). We further investigated potential variation according to estrogen receptor (ER) status, menopausal status and body mass index (BMI). Overall, 81.6 and 56.0% of women drank black or green tea, respectively. A total of 2,809 breast cancer cases were identified in the cohort. The multivariable model suggested an inverse association between black (≥5 vs. 0 cups/week: HR = 0.88, 95% CI 0.78, 1.00, p-trend = 0.08) and green tea (≥5 vs. 0 cups/week: HR = 0.82, 95% CI 0.70, 0.95, p-trend < 0.01) consumption and breast cancer risk. We did not observe differences by ER characteristics, menopausal status or BMI. In conclusion, our study suggests drinking at least five cups of green or black tea per week may be associated with decreased breast cancer risk.     

Tea intake and risk of colon cancer in African-Americans and Whites: North Carolina colon cancer study

Objectives: Tea polyphenols have been shown to exhibit anti-cancer activity, but the epidemiological findings are inconsistent. We examined the association between tea consumption and colon cancer in a population-based study in North Carolina. Methods: The analysis included 630 cases and 1040 controls frequency matched to cases by age, gender, and race. The odds ratios (OR) for tea consumption, adjusted for age and gender, were calculated for African-Americans and Whites and effect modification by race was explored. Results: No association was found between tea consumption and colon cancer overall. Compared to non-consumers, those who consumed <2 servings/r 2 servings/day had OR = 0.9 (95% CI: 0.7–1.2) and OR = 1.3 (95% CI: 0.9–1.8) respectively. Other risk factors for colorectal cancer (family history of colorectal cancer, exposure to non-steroid anti-inflammatory drugs, meat cooking practices, smoking, physical activity, body mass index, intake of red meat, fruits, vegetables, and alcoholic beverages) did not influence these associations. We did not find any evidence of effect modification by race on either on the multiplicative or additive scale. Conclusion: We conclude that, contrary to expectation, tea drinking did not decrease the risk of colon cancer in this study population.     

丹参茶的致突变性及致畸性试验

背景与目的：丹参茶是一种天然保健食品,为确保其食用安全,对其进行了致突变性和致畸性研究。材料与方法：材料主要用丹参茶浸泡液、大、小鼠和Ames试验菌株TA97、TA98、TA100、TA102;方法主要有小鼠精子畸形试验、小鼠胸骨髓微核试验、Ames试验及大鼠传统致畸试验。结果：3个剂量组的微核率和精子畸形率与阴性对照组比较差异无显著性,各剂量组的回变菌落数均未超过溶剂对照组的2倍,未见母体毒性、胚胎毒性和致畸性。结论：在本实验条件下,丹参茶未见致突变性和致畸性。     

Green-tea consumption and risk of stomach cancer: a population-based case-control study in Shanghai,China

The effect of drinking Chinese green tea on the risk of stomach cancer was evaluated in a population-based case-control study conducted in Shanghai, China, from October 1991 to December 1993. Eligible cases were incident cases of primary stomach cancer diagnosed during the study period among residents of Hongkou district and Nanhui county aged under 80 years. Controls were selected from the same street or commune where the case resided and were matched to the cases on age (within three years) and gender. A total of 711 cases and 711 matched controls, more than 90 percent of the eligible subjects, completed the interview. Information was obtained on the types of tea used, age when habitual tea drinking started, frequency of new batches of tea leaves used per day, number of cups brewed from each batch, total duration of drinking for each batch, strength and temperature of the tea consumed. Statistical analysis was based on modelling through conditional logistic regression. After adjusting for age, gender, place of residence, education, birthplace, alcohol consumption, and cigarette smoking, the odds ratio (OR) comparing drinkers of green tea with nondrinkers was 0.71 (95 percent confidence interval = 0.54–0.93). The adjusted OR decreased with increasing number of new batches of the green tea consumed each day (P value trend = 0.006). With the largest series of stomach cancer cases to date, this study found green-tea consumption associated with lower risk of stomach cancer. Among drinkers of green tea, the risk of stomach cancer did not depend on the age when habitual green-tea drinking started. Green tea may disrupt gastric carcinogenesis at both the intermediate and the late stages.This work was supported by US Public Health Service grant CA52560 from the National Cancer Institute, National Institutes of Health, Department of Health and Human Services.     

绿茶对明矾诱发遗传物质损伤的抑制作用

本实验以绿茶为材料,以明矾为诱变剂,以微核率作为DNA 损伤指标。结果含10 %绿茶饲料使明矾诱发的微核率从7167 ±1197 ‰降至3150 ±1105 ‰( P < 0101) 。表明绿茶对明矾诱发的DNA 损伤具有明显抑制作用。     

Higher regular coffee and tea consumption is associated with reduced endometrial cancer risk

Several studies have investigated the associations between diet and endometrial cancer, but few have focused specifically on coffee and tea. In a hospital‐based case–control study, we examined the associations between endometrial cancer risk and usual consumption of coffee, decaffeinated coffee, and black tea among 541 women with endometrial cancer and 541 women with an intact uterus but without a cancer diagnosis seen at Roswell Park Cancer Institute (Buffalo, New York) between 1982 and 1998. Daily frequency of consumption of coffee, decaffeinated coffee, and black tea in the few years prior to diagnosis in cases and questionnaire completion in controls was assessed with a self‐administered epidemiologic questionnaire and categorized as none, 0.5 cups/d, 1–2 cups/d and >2 cups/d. Odds ratios (OR) and 95% confidence intervals (CI) for each category referent to nondrinkers were estimated with unconditional logistic regression adjusting for age, endometrial cancer risk factors and each beverage mutually adjusted for other beverages. Compared to nondrinkers, we observed a nonsignificant negative association with endometrial cancer risk among women who reported >2 cups/d regular coffee (OR 0.71, 95% CI 0.49–1.03), a significant inverse association with >2 cups/d black tea (OR 0.56, 95% CI 0.35–0.90) and a significant inverse association with >4 cups/d combined coffee and tea consumption (OR 0.47, 95% CI 0.28–0.80). These findings suggest coffee and tea may be important in reducing endometrial cancer risk. © 2008 Wiley‐Liss, Inc.     

绿茶儿茶素对于人肝癌细胞的凋亡诱导作用

目的：探讨绿茶儿茶素（GTC）对BEL－7402人肝癌细胞的凋亡诱导作用。方法：应用透射电镜、流式细胞术、TUNEL和免疫组化等方法检测受100或200μg／ml GTC作用4天后的BEL－7402细胞的凋亡情况及其PCNA、bcl－2、c－myc、p53蛋白表达情况。结果：受GTC作用4天后的BEL－7402细胞的凋亡显著性增加,其PCNA表达显著性下降,而与凋亡相关的癌基因bcl－2、c－myc、p53蛋白表达未见明显改变。结论：GTC对于BEL－7402细胞的生长抑制作用可能与诱导细胞凋亡有关,也可能与抑制癌细胞DNA合成有关。本研究未发现GTC诱导BEL－7402细胞凋亡与bcl－2、c－myc、p53蛋白表达的相关性。     

Modulation of Arsenic Induced Cytotoxicity by Tea

Arsenic, a naturally ocurring chemical element, is considered hazardous to human health. Inorganic arsenic ‍compounds were found to induce cytotoxicity in Chinese hamster V-79 cells in culture. The arsenite form was more ‍toxic than arsenate. Extracts of green and two varieties of black tea, as well as their principal polyphenols, (-)- ‍epigallocatechingallate and theaflavin, efficiently counteracted the cytotoxic effects of arsenic compounds. On the ‍basis of the amount of tea extract that afforded 50% protection to the cells from arsenic induced cytotoxicity, black ‍tea was found to be as effective as green tea. The protective effect was attributable to the contents of not only (-)- ‍epigallocatechingallate but also of theaflavin, the latter being a predominant polyphenol present in black tea.     

通便袋泡茶的致突变性

背景与目的： 研究通便袋泡茶的潜在致突变性。 材料与方法： 采用常规的小鼠骨髓嗜多染红细胞微核试验、小鼠精子畸变试验和Ames试验。 结果： 通便袋泡茶小鼠骨髓嗜多染红细胞微核试验、小鼠精子畸形试验和Ames试验结果均为阴性。 结论： 在本试验条件下,通便袋泡茶无致突变作用。     

Combined inhibition of estrogen-dependent human breast carcinoma by soy and tea bioactive components in mice

Breast cancer is significantly less prevalent among Asian women, whose diets contain high intake of soy products and tea. The objective of our present study was to identify the combined effects of dietary soy phytochemicals and tea components on breast tumor progression in a clinically relevant in vivo model of MCF-7 androgen-dependent human breast tumor in female SCID mice. MCF-7 tumor growth, tumor cell proliferation and apoptosis, microvessel density, and expressions of tumor estrogen receptors were compared in mice treated with genistin-rich soy isoflavones (GSI), soy phytochemical concentrate (SPC), black tea (BT), green tea (GT), SPC/BT combination and SPC/GT combination. GSI and SPC led to dose-dependent inhibition of MCF-7 tumor growth via inhibition of cancer cell proliferation in vivo. GT showed more potent anti-breast tumor activity than BT. GT infusion at 1.5 g tealeaf/100 mL water produced significant (p < 0.05) reductions of 56% in final tumor weight. GT plus SPC at 0.1% of the diet further reduced final tumor weight by 72% (p < 0.005). Analysis of serum and tumor biomarkers showed that the combined effects of SPC and GT inhibited tumor angiogenesis, and reduced estrogen receptor (ER)-alpha and serum levels of insulin-like growth factor (IGF)-I. Our study suggests that dietary SPC plus GT may be used as a potential effective dietary regimen for inhibiting progression of estrogen-dependent breast cancer.     

上海市区胰腺癌全人群病例对照研究：——胰腺癌与烟,酒,绿茶的关系

在上海市区进行的基于全人的胰腺癌病例对照研究中，共访问了４５１例病人和１５５２例对照。研究表明在吸烟人群中发生胰腺癌的危险性上升，男女性的相对危险度分别为１．５和１．５。并且随着每天吸烟支数、吸烟的年限及包年数增加而升高，但随着开始吸烟的年龄或戒烟年数的上升而下降，男女饮酒的ＯＲ值无统计学上显著性意义。在调整了年龄、经济收入和每天吸烟支数之后，发现饮绿茶的女性发生胰腺癌的危险性有显著性的下降。但在     

绿茶对前列腺癌的化学预防作用

绿茶是许多国家和地区的重要饮料之一,近年来不断有体外和动物体内实验表明绿茶可以诱导前列腺癌细胞凋亡、抑制前列腺癌浸润及转移,流行病学调查及临床试验也发现绿茶对前列腺癌具有预防作用,可减少高分级前列腺上皮内瘤发展成为前列腺癌的概率,将有可能成为良好的前列腺癌化学预防物质.     

Urinary biomarkers of tea polyphenols and risk of colorectal cancer in the Shanghai Cohort Study

There have been no studies on specific tea polyphenol biomarkers and risk of colorectal cancer in humans. We prospectively examined the associations between validated biomarkers of specific tea polyphenols and risk of developing colorectal cancer among a cohort of 18,244 men in Shanghai, China, with 16 years of follow-up. Epigallocatechin (EGC), 4'-O-methyl-epigallocatechin (4'-MeEGC) and epicatechin, and their metabolites in baseline urine samples were measured on 162 incident colorectal cancer cases and 806 matched controls. Individuals with high prediagnostic urinary EGC levels had a lower risk of colon cancer. Compared with undetectable EGC, odds ratios (95% confidence interval) for colon cancer in the lowest, intermediate and highest tertile of detectable EGC were 0.64 (0.33-1.24), 0.60 (0.30-1.20) and 0.40 (0.19-0.83), respectively (p for trend = 0.02). A similar inverse relation between 4'-MeEGC and colon cancer also was observed. Compared with the lowest quartile, odds ratios (95% confidence intervals) for colon cancer in the 2nd, 3rd and 4th quartiles of urinary 4'-MeEGC were 0.49 (0.25-0.96), 0.32 (0.16-0.67) and 0.41 (0.20-0.84), respectively (p for trend = 0.006). The strongest protective effect was seen for regular tea drinkers who showed high levels of urinary EGC and 4'-MeEGC. No association between urinary levels of epicatechin or its metabolite and colon cancer risk was observed. Urinary levels of tea polyphenols and their metabolites were not associated with rectal cancer risk. The present study supports the notion of tea catechins as chemopreventive agents against the development of colon cancer in humans.