Comparison of white tea, green tea, epigallocatechin-3-gallate, and caffeine as inhibitors of PhIP-induced colonic aberrant crypts

Caffeine and Chlorogenic Acid Combination Attenuate Early-Stage Chemically Induced Colon Carcinogenesis in Mice: Involvement of oncomiR miR-21a-5p

Colorectal cancer (CRC) is one of most common cancers worldwide, with high rates of mortality. Epidemiological findings demonstrate that coffee consumption reduces the risk of developing CRC by ~13%. In general, in vivo and in vitro findings demonstrate the antiproliferative, antioxidant and proapoptotic effects of brewed coffee or major bioavailable coffee compounds. Thus, it was assessed whether caffeine (CAF) and/or chlorogenic acid (CGA) attenuates the early-stage of chemically induced mouse colon carcinogenesis. Male Swiss mice were submitted to a 1,2-dimethylhydrazine/deoxycholic acid (DMH/DCA)-induced colon carcinogenesis model. These animals received CAF (50 mg/kg), CGA (25 mg/kg) or CAF+CGA (50 + 25 mg/kg) intragastrically for five times/week for ten weeks. CAF+CGA had the most pronounced effects on decreasing epithelial cell proliferation (Ki-67) and increasing apoptosis (cleaved caspase-3) in colonic crypts. This treatment also decreased the levels of proinflammatory cytokines IL-6, IL-17 and TNF-α, and downregulated the oncomiR miR-21a-5p in the colon. Accordingly, the analysis of miR-21a-5p targets demonstrated the genes involved in the negative regulation of proliferation and inflammation, and the positive regulation of apoptosis. Ultimately, CAF+CGA attenuated preneoplastic aberrant crypt foci (ACF) development. Our findings suggest that a combination of coffee compounds reduces early-stage colon carcinogenesis by the modulation of miR-21a-5p expression, highlighting the importance of coffee intake to prevent CRC.

Animal Models of Colorectal Cancer: From Spontaneous to Genetically Engineered Models and Their Applications

Colorectal cancer is one of the most common gastrointestinal malignancies in humans, affecting approximately 1.8 million people worldwide. This disease has a major social impact and high treatment costs. Animal models allow us to understand and follow the colon cancer progression; thus, in vivo studies are essential to improve and discover new ways of prevention and treatment. Dietary natural products have been under investigation for better and natural prevention, envisioning to show their potential. This manuscript intends to provide the readers a review of rodent colorectal cancer models available in the literature, highlighting their advantages and disadvantages, as well as their potential in the evaluation of several drugs and natural compounds’ effects on colorectal cancer.

Effects of Coffee and Its Components on the Gastrointestinal Tract and the Brain-Gut Axis

Coffee is one of the most popular beverages consumed worldwide. Roasted coffee is a complex mixture of thousands of bioactive compounds, and some of them have numerous potential health-promoting properties that have been extensively studied in the cardiovascular and central nervous systems, with relatively much less attention given to other body systems, such as the gastrointestinal tract and its particular connection with the brain, known as the brain–gut axis. This narrative review provides an overview of the effect of coffee brew; its by-products; and its components on the gastrointestinal mucosa (mainly involved in permeability, secretion, and proliferation), the neural and non-neural components of the gut wall responsible for its motor function, and the brain–gut axis. Despite in vitro, in vivo, and epidemiological studies having shown that coffee may exert multiple effects on the digestive tract, including antioxidant, anti-inflammatory, and antiproliferative effects on the mucosa, and pro-motility effects on the external muscle layers, much is still surprisingly unknown. Further studies are needed to understand the mechanisms of action of certain health-promoting properties of coffee on the gastrointestinal tract and to transfer this knowledge to the industry to develop functional foods to improve the gastrointestinal and brain–gut axis health.

Dietary natural methylxanthines and colorectal cancer: a systematic review and meta-analysis

Some evidence suggests that caffeine, theophylline, and theobromine, as natural methylxanthines (MTXs), possess anti-cancer effects.

Drinking for protection? Epidemiological and experimental evidence on the beneficial effects of coffee or major coffee compounds against gastrointestinal and liver carcinogenesis

Recent meta-analyses indicate that coffee consumption reduces the risk for digestive tract (oral, esophageal, gastric and colorectal) and, especially, liver cancer. Coffee bean-derived beverages, as the widely-consumed espresso and "common" filtered brews, present remarkable historical, cultural and economic importance globally. These drinks have rich and variable chemical composition, depending on factors that vary from "seeding to serving". The alkaloids caffeine and trigonelline, as well as the polyphenol chlorogenic acid, are some of the most important bioactive organic compounds of these beverages, displaying high levels in both espresso and common brews and/or increased bioavailability after consumption. Thus, we performed a comprehensive literature overview of current knowledge on the effects of coffee beverages and their highly bioavailable compounds, describing: 1) recent epidemiological and experimental findings highlighting the beneficial effects against gastrointestinal/liver carcinogenesis, and 2) the main molecular mechanisms in these in vitro and in vivo bioassays. Findings predominantly address the protective effects of coffee beverages and their most common/bioavailable compounds individually on gastrointestinal and liver cancer development. Caffeine, trigonelline and chlorogenic acid modulate common molecular targets directly implicated in key cancer hallmarks, what could stimulate novel translational or population-based mechanistic investigations.

Coffee, but Neither Decaffeinated Coffee nor Caffeine, Elicits Chemoprotection Against a Direct Carcinogen in the Colon of Wistar Rats

Colorectal cancer (CRC) is the third most frequent malignancy worldwide. Coffee is the second most consumed drink in the globe and suggested to decrease the CRC risk. Here, we explored whether coffee, decaffeinated coffee, or caffeine impact on the development of colorectal carcinogenesis induced by the direct carcinogen N-methyl-N-nitro-N-nitrosoguanidine (MNNG) in rats. To this end, sixty-four young male Wistar rats were divided into eight groups of eight animals each. We analyzed the frequency of dysplastic crypts and expression of metallothionein as a biomarker of the cancer risk, as well the expression of phosphorylated H2A histone family/member X (γH2AX) for DNA damage and cyclooxygenase-2 (COX-2) for inflammatory response. We also studied the oxidative stress profile in hepatic and colonic frozen samples (malondialdehyde [MDA], glutathione [GSH], and α-tocopherol). We found that coffee but neither decaffeinated coffee nor caffeine decreased the development of dysplastic crypts in MNNG-exposed rats. All treatments reduced DNA damage intensity in colonocytes. Only decaffeinated coffee increased the numbers of metallothionein positive crypts in comparison with coffee-treated rats. Coffee and caffeine inhibited COX-2 expression in the colon. Both decaffeinated coffee and caffeine decreased hepatic α-tocopherol levels. We suggest that coffee may have other compounds that elicit greater chemoprotective effects than caffeine reducing the CRC risk.

Effects of Dietary Fibre from the Traditional Indonesian Food, Green Cincau (Premna oblongifolia Merr.) on Preneoplastic Lesions and Short Chain Fatty Acid Production in an Azoxymethane Rat Model of Colon Cancer

Green cincau (Premna oblongifolia Merr.) is a traditional food of Indonesia and provides a natural source of dietary fibre and antioxidants. This study evaluated the ability of green cincau, and other dietary fibres with or without the addition of anti-oxidant, epigallocatechin-3-gallate (EGCG), to prevent colorectal cancer in a 12 week azoxymethane (AOM) rat model. While all dietary treatments stimulated short chain fatty acid production (SCFA) in the digesta and faeces, no one treatment was able to significantly protect against aberrant crypt formation (ACF), when compared to the control diet. However, feeding green cincau leaves or extracts did not result in an increase in ACF compared to the control diet. Unexpectedly, when the dietary fibre source was pectin, 0.1% EGCG increased proliferative activity and liver lipid peroxidation when compared to the control diet containing cellulose. Examination of faecal microbial communities identified the presence of short chain acid producing bacteria, but a distinct community profile was not observed from any individual diet group. Overall, this research implies that combining dietary fibre with an antioxidant does not automatically equate to a beneficial response. Further work is required to investigate the health-promoting properties of green cincau.

Consumption of the total Western diet differentially affects the response to green tea in rodent models of chronic disease compared to the AIN93G diet

SCOPE

In pre-clinical studies investigating bioactive components, the efficacy of the bioactive is likely influenced by the basal diet provided to rodents. In this study, we hypothesized that a model bioactive, green tea extract (GTE), would have different effects on colon carcinogenesis, body composition, and lipid metabolism in mice fed a basal diet formulated to promote animal health and growth (AIN93G) as compared to a Western diet that emulates typical American intakes of micro- and macronutrients, the total Western diet (TWD).

METHODS AND RESULTS

Mice were fed either AIN93G or TWD, with or without GTE added to drinking water for 18 weeks. Aberrant crypt foci (ACF) in azoxymethane-initiated mice was nearly three times greater in mice fed TWD compared to AIN93G. Consumption of GTE suppressed ACF development only in mice fed the TWD. Similarly, supplementation with GTE suppressed weight gain and fasted glucose only in mice fed TWD, while GTE suppressed fat mass in mice fed either diet. Irrespective of diet, GTE supplementation increased cecum weight and decreased cecal SCFA concentration.

CONCLUSION

Collectively, these observations indicate that the TWD influences the bioactivity of GTE in rodent models of obesity, metabolism, and carcinogenesis.

Statistical Approaches to Assess the Association between Phenolic Compounds and the in vitro Antioxidant Activity of Camellia sinensis and Ilex paraguariensis Teas

Tea presents a diverse phenolic composition which is responsible for its alleged biological activities, including the in vivo and in vitro antioxidant capacity. It is very usual to find researches applying statistical methods, such as analysis of variances (ANOVA) and linear Pearson correlation coefficients to analyze the strength of correlation between phenolic composition and the in vitro antioxidant activity of teas from Camellia sinensis (green, black, white, oolong, red, and yellow teas) and Ilex paraguariensis (Yerba-mate), which are the most produced and consumed types of teas. However, evidence has shown that these approaches are not as suitable as multivariate statistical methods once they do not depict nor show association among all results and variables simultaneously, making it difficult to understand clearly the data structure and patterns. Then, the objective of this work is to review and explain some univariate/bivariate and multivariate statistical techniques used to assess the association between phenolic compounds and the in vitro antioxidant activity of green, white, black, red, yellow, oolong and Yerba-mate teas. Moreover, this paper provides an overview on some assays used to estimate the in vitro antioxidant capacity of teas.

Green tea and liver cancer risk: A meta-analysis of prospective cohort studies in Asian populations

OBJECTIVES

The aim of this meta-analysis was to investigate whether an association existed between green tea consumption and the risk for liver cancer in prospective cohort studies in Asian populations.

METHODS

Relevant studies were identified by searching PubMed, EMBASE, ISI Web of Science, and the Chinese Bio-medicine Database published before April 2015. Study-specific risk estimates for the highest versus non- or lowest and increment of daily cup of green tea consumption levels were combined based on fixed- or random-effects models. STATA 11.0 (Stata Corporation, College Station, TX, USA) software was used for statistical analysis.

RESULTS

Nine prospective cohort articles involving 465,274 participants and 3694 cases of liver cancer from China, Japan, and Singapore were included. The summary relative risk (RR) indicated a significant association between the highest green tea consumption and reduced risk for liver cancer (summary RR, 0.88; 95% confidence interval [CI], 0.81-0.97). However, no statistically significant association was observed when analyzing daily consumption of one cup (summary RR, 0.97; 95% CI, 0.95-1.00). When stratified by sex, the protective effect of green tea consumption on risk for liver cancer was observed only in the group of women (summary RR, 0.78; 95% CI, 0.64-0.96), but not in men (summary RR, 0.89; 95% CI, 0.79-1.00).

CONCLUSIONS

The present analysis indicated the preventive effects of green tea intake on the risk for liver cancer in female Asian populations. However, additional studies are needed to make a convincing case for this association.

Coffee and tea consumption, genotype-based CYP1A2 and NAT2 activity and colorectal cancer risk-results from the EPIC cohort study

Coffee and tea contain numerous antimutagenic and antioxidant components and high levels of caffeine that may protect against colorectal cancer (CRC). We investigated the association between coffee and tea consumption and CRC risk and studied potential effect modification by CYP1A2 and NAT2 genotypes, enzymes involved in the metabolization of caffeine. Data from 477,071 participants (70.2% female) of the European Investigation into Cancer and Nutrition (EPIC) cohort study were analyzed. At baseline (1992-2000) habitual (total, caffeinated and decaffeinated) coffee and tea consumption was assessed with dietary questionnaires. Cox proportional hazards models were used to estimate adjusted hazard ratio's (HR) and 95% confidence intervals (95% CI). Potential effect modification by genotype-based CYP1A2 and NAT2 activity was studied in a nested case-control set of 1,252 cases and 2,175 controls. After a median follow-up of 11.6 years, 4,234 participants developed CRC (mean age 64.7 ± 8.3 years). Total coffee consumption (high vs. non/low) was not associated with CRC risk (HR 1.06, 95% CI 0.95-1.18) or subsite cancers, and no significant associations were found for caffeinated (HR 1.10, 95% CI 0.97-1.26) and decaffeinated coffee (HR 0.96, 95% CI 0.84-1.11) and tea (HR 0.97, 95% CI 0.86-1.09). High coffee and tea consuming subjects with slow CYP1A2 or NAT2 activity had a similar CRC risk compared to non/low coffee and tea consuming subjects with a fast CYP1A2 or NAT2 activity, which suggests that caffeine metabolism does not affect the link between coffee and tea consumption and CRC risk. This study shows that coffee and tea consumption is not likely to be associated with overall CRC.

Prospective cohort study of tea consumption and risk of digestive system cancers: results from the Shanghai Women's Health Study

BACKGROUND

Data from in vitro and animal studies support a protective role for tea in the etiology of digestive system cancers; however, results from prospective cohort studies have been inconsistent. In addition, to our knowledge, no study has investigated the association of tea consumption with the incidence of all digestive system cancers in Chinese women.

OBJECTIVE

We investigated the association of regular tea intake (≥3 times/wk for >6 mo) with risk of digestive system cancers.

DESIGN

We used the Shanghai Women's Health Study, a population-based prospective cohort study of middle-aged and older Chinese women who were recruited in 1996-2000. Adjusted HRs and associated 95% CIs were derived from Cox regression models.

RESULTS

After a mean follow-up of 11 y, 1255 digestive system cancers occurred (stomach, esophagus, colorectal, liver, pancreas, and gallbladder/bile duct cancers) in 69,310 nonsmoking and non-alcohol-drinking women. In comparison with women who never drank tea, regular tea intake (mostly green tea) was associated with reduced risk of all digestive system cancers combined (HR: 0.86; 95% CI: 0.74, 0.98), and the reduction in risk increased as the amount and years of tea consumption increased (P-trend = 0.01 and P-trend < 0.01, respectively). For example, women who consumed ≥150 g tea/mo (∼2-3 cups/d) had a 21% reduced risk of digestive system cancers combined (HR: 0.79; 95% CI: 0.63, 0.99). The inverse association was found primarily for colorectal and stomach/esophageal cancers.

CONCLUSION

In this large prospective cohort study, tea consumption was associated with reduced risk of colorectal and stomach/esophageal cancers in Chinese women.

Modulation of Wnt/β-catenin signaling pathway by bioactive food components

The Wnt/β-catenin signaling pathway, one of the most conserved intercellular signaling cascade, is a known regulator of cellular functions related to tumor initiation and progression, cell proliferation, differentiation, survival and adhesion. Because aberrant Wnt/β-catenin signaling has been observed in a variety of human cancers including a majority of colorectal cancers, about half of prostate cancers and a third of melanomas, inhibitors of its complex signaling pathways are being investigated for therapy as well as chemoprevention of these cancers. During the last decade, several naturally occurring dietary agents have been shown to target intermediates in the Wnt/β-catenin signaling pathway. In this review, we highlight the current understanding of the Wnt/β-catenin signaling pathway and present an analysis of the key findings from laboratory studies on the effects of a panel of dietary agents against a variety of cancers. Promise of these agents for treating and preventing human cancer is then discussed.

Effects of the aqueous extract of white tea (Camellia sinensis) in a streptozotocin-induced diabetes model of rats

White tea (WT) is very similar to green tea (GT) but it is exceptionally prepared only from the buds and young tea leaves of Camelia sinensis plant while GT is prepared from the matured tea leaves. The present study was investigated to examine the effects of a 0.5% aqueous extract of WT in a streptozotocin-induced diabetes model of rats. Six-week-old male Sprague-Dawley rats were divided into 3 groups of 6 animals in each group namely: normal control (NC), diabetic control (DBC) and diabetic white tea (DWT). Diabetes was induced by an intraperitoneal injection of streptozotocin (65 mg/kg BW) in DBC and DWT groups except the NC group. After 4 weeks feeding of 0.5% aqueous extracts of WT, the drink intake was significantly (P<0.05) increased in the DWT group compared to the DBC and NC groups. Blood glucose concentrations were significantly decreased and glucose tolerance ability was significantly improved in the DWT group compared to the DBC group. Liver weight and liver glycogen were significantly increased and serum total cholesterol and LDL-cholesterol were significantly decreased in the DWT group compared to the DBC group. The food intake, body weight gain, serum insulin and fructosamine concentrations were not influenced by the consumption of WT. Data of this study suggest that the 0.5% aqueous extract of WT is effective to reduce most of the diabetes associated abnormalities in a steptozotocin-induced diabetes model of rats.

Green tea polyphenol sensing

Green tea polyphenols have emerged over the past two decades as an important dietary factor for health promotion. There is considerable evidence that tea polyphenols, in particular (-)-epigallocatechin-3-gallate (EGCG) inhibit carcinogenesis. However, the mechanisms for the cancer-preventive activity of EGCG are not completely characterized and many features remain to be elucidated. Recently we have identified a cell-surface EGCG receptor and the relating molecules that confer EGCG responsiveness to many cancer cells at physiological concentrations. Here, we review some of the reported mechanisms for the cancer chemopreventive action of EGCG and provide an overview of several molecules that sense and manage the physiological functions of EGCG.

Combination of curcumin and green tea catechins prevents dimethylhydrazine-induced colon carcinogenesis

The chemopreventive effects of curcumin and green tea catechins individually and in combination on 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis were studied in male Wister rats following 32 weeks of dietary treatment. The incidence, number and size of colorectal cancer were measured. Colorectal aberrant crypt foci (ACF) were analyzed by methylene blue staining. Proliferation indices and apoptotic indices were determined by PCNA immunostaining and TUNEL assay, respectively. The results showed that dietary curcumin, catechins and combination administration significantly inhibited the total number of ACF per rat. The combination treatment displayed the most potent inhibitory effect, while there was no difference of inhibition between curcumin and catechins-treated groups. The incidence of colorectal cancer in the treated groups was significantly lower than that of positive control group. Compared with the positive control group, the proliferation index was significantly decreased and the apoptotic index was significantly increased in all treatment groups, while the effect of the combination was the greatest among the treated groups. Our findings suggest that the combination of curcumin and catechins may produce a synergistic colon cancer-preventative effect that would be more potent than each of the compounds alone.

Meat and cancer

An increasing literature associates high intake of meat, especially red meat and processed meat with an increased risk of cancers, especially colorectal cancer. There is evidence that this risk may not be a function of meat per se, but may reflect high-fat intake, and/or carcinogens generated through various cooking and processing methods. The cancer risk may be modulated by certain genotypes. Cancers associated with high meat consumption may be reduced by the addition of anticarcinogens in the diet, especially at the same time as meat preparation or meat consumption, or modification of food preparation methods. Meat contains potential anticarcinogens, including omega-3 polyunsaturated fatty acids, and conjugated linoleic acid (CLA). Red meat, in particular, is an important source of micronutrients with anticancer properties, including selenium, vitamin B6 and B12, and vitamin D. Adjusting the balance between meat and other dietary components may be critical to protecting against potential cancer risks.

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

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.

Carvacrol facilitates heat-induced inactivation of Escherichia coli O157:H7 and inhibits formation of heterocyclic amines in grilled ground beef patties

Heating meat at high temperature and/or for a long time to kill foodborne pathogens increases the formation of potentially carcinogenic heterocyclic amines. To overcome this problem, 1% carvacrol, the main ingredient of oregano oil widely used in salad dressings, was added to ground beef, which was mixed well and then inoculated with Escherichia coli O157:H7. Beef patties were then prepared and heat-treated on a preheated electrical skillet to reach an internal temperature of 65, 70, or 80 degrees C at the cold spot. Samples were enumerated for surviving E. coli O157:H7 population by plating on appropriate media. Heterocyclic amines (MeIQ, MeIQx, and PhIP) were extracted from ground beef using solid phase extraction and analyzed by mass spectrometry. Multiple reaction monitoring (MRM) scan type in positive mode was used to monitor the amines of interest. Compared to controls, the population of E. coli O157:H7 was reduced by 2.5-5 logs. The corresponding highest reductions in the three major amines were MeIQ, 58%; MeIQx, 72%; and PhIP, 78%. The results show that carvacrol concurrently reduced E. coli O157:H7 and amines in a widely consumed meat product. Possible mechanisms of the beneficial effects and dietary significance of the results are discussed.

Antioxidative and anti-carcinogenic activities of tea polyphenols

Tea (Camellia sinensis, Theaceace), a popular beverage consumed world-wide, has been studied for its preventive effects against cancer as well as cardiovascular, neurodegenerative, and other diseases. Most of the proposed beneficial effects have been attributed to the polyphenolic compounds in tea, but the nature of these activities and the molecular mechanisms of their actions remain unclear. Tea polyphenols are known to be strong antioxidants. Prevention of oxidative stress, modulation of carcinogen metabolism, and prevention of DNA damage have been suggested as possible cancer preventive mechanisms for tea and tea polyphenols. In this chapter, we discuss these topics in the light of biotransformation and bioavailability of tea polyphenols. We also review the preventive effects of tea polyphenols in animal models of carcinogenesis and some of the possible post-initiation mechanisms of action. Finally, we discuss the effects of tea consumption on cancer risk in humans. It is our aim to raise some of the unanswered questions regarding cancer prevention by tea and to stimulate further research in this area.

Protective effects of epigallocatechin gallate on colon preneoplastic lesions induced by 2-amino-3-methylimidazo[4,5-f ] quinoline in mice

Epigallocatechin gallate (EGCG), a key active ingredient in green tea, has multiple anticarcinogenic effects. The aim of the present study was to investigate if EGCG could prevent the formation of colon aberrant crypt foci (ACF) induced by 2-amino-3-methylimidazo[4,5-f ]quinoline (IQ) and to explore possible mechanisms for resultant effects. Sixty male BALB/cA nude, immunodeficient mice were divided into six groups including a normal unexposed control, mice induced with IQ alone, three groups treated with varying doses of EGCG post-IQ induction, and a EGCG-treated control population. Six weeks later, the mice were killed, and tissues subjected to hematoxylin-eosin (H&E) and 0.2% methylene blue staining to observe histopathological alterations of colon mucus and the formation of ACF, respectively. Protein expression of NF-E2-related factor 2 (Nrf2) was assessed via immunohistochemistry (IHC) and Western analysis, and mRNA levels of Nrf2 and uridine 5'-diphosphate-glucuronosyltransferase (UGT)1A10 were determined in colon tissues. Our results demonstrate that, compared with IQ-induced controls, the degree of atypical hyperplasia decreased and the number of total ACF and total AC also decreased significantly (P < 0.05 and P < 0.01, respectively) in mice belonging to all EGCG dosing groups. At the same time, the protein levels of Nrf2 detected by IHC and Western blotting increased (both P < 0.01 compared with IQ group), and the mRNA levels of Nrf2 and UGT1A10 increased (both P < 0.01 compared with IQ group). In conclusion, EGCG had preventive effects on preneoplastic lesions induced by IQ. Our observations suggest that this effect may be the result of activation of the Nrf2-UGT1A10 signaling pathway.

Protective versus promotional effects of white tea and caffeine on PhIP-induced tumorigenesis and beta-catenin expression in the rat

A 1 year carcinogenicity bioassay was conducted in rats treated with three short cycles of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)/high-fat (HF) diet, followed by 2% white tea (wt/vol), 0.05% epigallocatechin-3-gallate (EGCG) or 0.065% caffeine as sole source of fluid intake. Thirty-two percent of the PhIP/HF controls survived to 1 year, compared with 50, 48.7 and 18.2% in groups given white tea, EGCG and caffeine, respectively. After 1 year, PhIP/HF controls had tumors in the colon, skin, small intestine, Zymbal's gland, salivary gland and pancreas. For all sites combined, excluding the colon, tumor incidence data were as follows: PhIP/HF 69.5%, PhIP/HF + EGCG 48.7%, PhIP/HF + white tea 46.9% and PhIP/HF + caffeine 13.3%. Unexpectedly, a higher incidence of colon tumors was detected in rats post-treated with white tea (69%) and caffeine (73%) compared with the 42% incidence in PhIP/HF controls. In the colon tumors, beta-catenin mutations were detected at a higher frequency after caffeine posttreatment, and there was a shift toward more tumors harboring substitutions of Gly34 with correspondingly high protein and messenger RNA expression seen for both beta-catenin and c-Myc. c-Myc expression exhibited concordance with tumor promotion, and there was a concomitant increase in cell proliferation versus apoptosis in colonic crypts. A prior report described suppression of PhIP-induced colonic aberrant crypts by the same test agents, but did not incorporate a HF diet. These findings are discussed in the context of epidemiological data which do not support an adverse effect of tea and coffee on colon tumor outcome-indeed, some such studies suggest a protective role for caffeinated beverages.