Modulation of N-nitrosomethylbenzylamine metabolism by black raspberries in the esophagus and liver of Fischer 344 rats

Black Raspberry Extract Enhances Glutathione Conjugation of the Fjord-Region Diol Epoxide Derived from the Tobacco Carcinogen Dibenzo[def,p]chrysene in Human Oral Cells

In a series of previous studies we reported that black raspberry (BRB) powder inhibits dibenzo[a,l]pyrene (DBP)-induced DNA damage, mutagenesis, and oral squamous cell carcinoma (OSCC) development in mice. In the present study, using human oral leukoplakia (MSK-Leuk1) and squamous cell carcinoma (SCC1483) cells, we tested the hypothesis that BRB extract (BRBE) will enhance the synthesis of glutathione (GSH) and in turn increase GSH conjugation of the fjord-region DBP diol epoxide (DBPDE) derived from DBP leading to inhibition of DBP-induced DNA damage. The syntheses of DBPDE-GSH conjugate, DBPDE-dA adduct, and the corresponding isotope-labeled internal standards were performed; LC-MS/MS methods were used for their quantification. BRBE significantly (p < 0.05) increased cellular GSH by 31% and 13% at 6 and 24 h, respectively, in OSCC cells; in MSK-LeuK1 cells, the levels of GSH significantly (p < 0.05) increased by 55% and 22%, at 1 and 6 h. Since BRBE significantly enhanced the synthesis of GSH in both cell types, subsequent experiments were performed in MSK-Leuk1 cells. Western blot analysis was performed to determine the types of proteins involved in the synthesis of GSH. BRBE significantly (p < 0.05) increased the protein expression (2.5-fold) of the glutamate-cysteine ligase catalytic subunit (GCLC) but had no effect on the glutamate-cysteine ligase modifier subunit (GCLM) and glutathione synthetase (GSS). LC-MS/MS analysis showed that pretreatment of cells with BRBE followed by DBPDE significantly (p < 0.05) increased the levels of DBPDE-GSH conjugate (2.5-fold) and decreased DNA damage by 74% measured by assessing levels of DBPDE-dA adduct formation. Collectively, the results of this in vitro study clearly support our hypothesis, and the LC-MS/MS methods developed in the present study will be highly useful in testing the same hypothesis initially in our mouse model and ultimately in smokers.

Chemopreventive Effect of Dietary Anthocyanins against Gastrointestinal Cancers: A Review of Recent Advances and Perspectives

Anthocyanins are a group of dietary polyphenols, abundant mainly in fruits and their products. Dietary interventions of anthocyanins are being studied extensively related to the prevention of gastrointestinal (GI) cancer, among many other chronic disorders. This review summarizes the hereditary and non-hereditary characteristics of GI cancers, chemistry, and bioavailability of anthocyanins, and the most recent findings of anthocyanin in GI cancer prevention through modulating cellular signaling pathways. GI cancer-preventive attributes of anthocyanins are primarily due to their antioxidative, anti-inflammatory, and anti-proliferative properties, and their ability to regulate gene expression and metabolic pathways, as well as induce the apoptosis of cancer cells.

A nutrigenetic approach for investigating the chemopreventive effects of black raspberries during the development of preneoplastic esophagi in rats

BACKGROUND

Large epidemiological studies have shown that diets high in fruits reduce the risk of esophageal squamous cell carcinoma (ESCC).

OBJECTIVE

The current study investigated the effects of black raspberries (BRBs) on gene expression during the development of preneoplastic esophagi in rats.

METHODS

Using a post-initiation protocol, F344 rats were injected with N-nitrosomethylbenzylamine (NMBA) and then fed either a control diet or 5% BRBs. At weeks 9, 15, and 35, we euthanized subgroups of the rats and collected preneoplastic esophagi to isolate RNA samples for DNA microarray.

RESULTS

Along the development of NMBA-induced preneoplastic esophagi, NMBA injections led to differential expression of 1181 genes comparing to control rats, and dietary BRBs modulated 428 genes in esophagi from NMBA-treated rats. There are 137 common genes between 1181 and 428 gene sets, and BRBs significantly reversed the expression of 133 genes. These genes are associated with multiple gene oncology functions. BRBs induced an 8.8-fold gene enrichment on the pathway of inflammatory response and regulated 10 genes involved in this pathway. Among them, BRBs significantly reversed the expression of pro-inflammatory cytokines, such as CCL2, S100A8, and IL19.

CONCLUSIONS

BRBs exhibit strong anti-inflammatory effects against NMBA-induced rat esophageal tumorigenesis.

Inhibition of the development of N-nitrosomethylbenzylamine-induced esophageal tumors in rats by strawberries and aspirin, alone and in combination

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is one of two subtypes of esophageal cancer, with high incidence and mortality rates in developing countries.

OBJECTIVE

The current study investigated the potential chemoprotective effects of strawberries and aspirin against the development of rat esophageal papillomas, the precursors to ESCC.

METHODS

Using a prevention model, we administered study diets to rats before, during, and after N-nitrosomethylbenzylamine (NMBA) treatment. The effects of the four diets were evaluated: the control diet, 5% strawberry powder in the control diet, 0.01% aspirin in the drinking water, and the combination of strawberries and aspirin. At week 25, we euthanized all the rats and collected their esophagi to quantify tumor incidence, multiplicity, and burden, as well as for molecular analysis.

RESULTS

Both strawberries and aspirin significantly decreased esophageal tumor multiplicity, with the combination causing the most robust suppression. Aspirin alone and the combination decreased the total tumor burden in the esophagus. None of the diets had a significant effect on tumor incidence or the expression of COX-1 and COX-2. Strawberries and aspirin, alone and in combination, significantly suppressed squamous epithelial cell proliferation (PCNA).

CONCLUSIONS

Strawberries, aspirin, and their combination exhibit chemoprotective effects against NMBA-induced esophageal tumors in rats.

Potential Benefits of Edible Berries in the Management of Aerodigestive and Gastrointestinal Tract Cancers: Preclinical and Clinical Evidence

Epidemiological reports as well as experimental studies have demonstrated the significant health benefits provided by regular berry consumption. Berries possess both prophylactic and therapeutic potential against several chronic illnesses, such as cardiovascular, neurodegenerative, and neoplastic diseases. Berries owe their health benefits to phytoconstituents, such as polyphenolic anthocyanins, ellagic acid, and a diverse array of phytochemicals bestowed with potent antioxidant and anti-inflammatory effects as well as the ability to engage a multitude of signaling pathways. This review highlights the principal chemical constituents present in berries and their primary molecular targets. The article presents and critically analyzes the chemopreventive and therapeutic potential of berry extracts, fractions, and bioactive components on various cancers of the gastrointestinal tract (GIT), including esophageal, stomach, intestinal, and colorectal cancers as well as cancers of the upper aerodigestive tract, such as oral cancer. The current status of clinical studies evaluating berry products in several aforementioned cancers is presented. Various emerging issues including dose-ranging and dosage forms, the role of synergy and the usage of combination therapy as well as other relevant areas essential for the development of berry phytoconstituents as mainstream chemopreventive and therapeutic agents against aerodigestive and GIT cancers are critically discussed.

Protective Role of Dietary Berries in Cancer

Dietary patterns, including regular consumption of particular foods such as berries as well as bioactive compounds, may confer specific molecular and cellular protection in addition to the overall epidemiologically observed benefits of plant food consumption (lower rates of obesity and chronic disease risk), further enhancing health. Mounting evidence reports a variety of health benefits of berry fruits that are usually attributed to their non-nutritive bioactive compounds, mainly phenolic substances such as flavonoids or anthocyanins. Although it is still unclear which particular constituents are responsible for the extended health benefits, it appears that whole berry consumption generally confers some anti-oxidant and anti-inflammatory protection to humans and animals. With regards to cancer, studies have reported beneficial effects of berries or their constituents including attenuation of inflammation, inhibition of angiogenesis, protection from DNA damage, as well as effects on apoptosis or proliferation rates of malignant cells. Berries extend effects on the proliferation rates of both premalignant and malignant cells. Their effect on premalignant cells is important for their ability to cause premalignant lesions to regress both in animals and in humans. The present review focuses primarily on in vivo and human dietary studies of various berry fruits and discusses whether regular dietary intake of berries can prevent cancer initiation and delay progression in humans or ameliorate patients’ cancer status.

Black raspberries suppress colonic adenoma development in ApcMin/+ mice: relation to metabolite profiles

Freeze-dried black raspberries (BRBs) have demonstrated chemopreventive effects in a dietary intervention trial with human colorectal cancer patients. The aim of this study was to investigate BRB-caused metabolite changes using the Apc(Min/+) mouse as a model of human colorectal cancer. Wild-type (WT) mice were fed control diet, and Apc(Min/+) mice were fed either control diet or control diet supplemented with 5% BRBs for 8 weeks. Colonic and intestinal polyp size and number were measured. A non-targeted metabolomic analysis was conducted on colonic mucosa, liver and fecal specimens. Eight weeks of BRB treatment significantly decreased intestinal and colonic polyp number and size in Apc(Min/+) mice. The apc gene mutation significantly changed 52 metabolites in colonic mucosa associated with increased amino acid and decreased lipid metabolites, as well as 39 liver and 8 fecal metabolites. BRBs significantly reversed 23 apc-regulated metabolites, including 13 colonic mucosa, 8 liver and 2 fecal metabolites that were involved in amino acid, glutathione, lipid and nucleotide metabolism. Of these, changes in eight metabolites were linearly correlated with decreased colonic polyp number and size in BRB-treated Apc(Min/+) mice. Elevated levels of putrescine and linolenate in Apc(Min/+) mice were significantly decreased by BRBs. Ornithine decarboxylase expression, the key enzyme in putrescine generation, was fully suppressed by BRBs. These results suggest that BRBs produced beneficial effects against colonic adenoma development in Apc(Min/+) mice and modulated multiple metabolic pathways. The metabolite changes produced by BRBs might potentially reflect the BRB-mediated chemopreventive effects in colorectal cancer patients.

Protective effects of blueberries (Vaccinium corymbosum L.) extract against cadmium-induced hepatotoxicity in mice

The oxidative status and morphological changes of mouse liver exposed to cadmium chloride (Cd(II)) and therapeutic potential of blueberry (Vaccinium corymbosum L.) extract against Cd(II)-induced hepatic injury were investigated. A variety of parameters were evaluated, including lipid peroxidation (LPO), protein carbonyl (PCO) level, DNA fragment, as well as antioxidative defense system (i.e., superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH)). Elemental analysis and evaluation of morphological changes and NO levels were also performed. Exposure to Cd(II) led to increased LPO and PCO as well as DNA fragment and a reduction of SOD and CAT activities, however, the content of GSH elevated probably due to biological adaptive-response. In contrast, co-treatment of anthocyanin (Ay) inhibited the increased oxidative parameters as well as restored the activities of antioxidative defense system in a dose-dependent manner. Ay administration regained these morphological changes caused by intoxication of Cd(II) to nearly normal levels. Moreover, the accumulation of Cd(II) in liver may be one of the reasons for Cd(II) toxicity and Ay can chelate with Cd(II) to reduce Cd(II) burden. The influence of Cd(II) on the Zn and Ca levels can also be adjusted by the co-administration of Ay. Exposure to Cd(II) led to an increase of NO and Ay reduced NO contents probably by directly scavenging. Potential mechanisms for the protective effect of Ay have been proposed, including its anti-oxidative and anti-inflammatory effect along with the metal-chelating capacity. These results suggest that blueberry extract may be valuable as a therapeutic agent in combating Cd(II)-induced tissue injury.

Inhibition of lung tumor development by berry extracts in mice exposed to cigarette smoke

Cigarette smoke (CS) and dietary factors play a major role in cancer epidemiology. At the same time, however, the diet is the richest source of anticancer agents. Berries possess a broad array of health protective properties and were found to attenuate the yield of tumors induced by individual carcinogens in the rodent digestive tract and mammary gland but failed to prevent lung tumors induced by typical CS components in mice. We exposed whole-body Swiss ICR mice to mainstream CS, starting at birth and continuing daily for 4 months. Aqueous extracts of black chokeberry and strawberry were given as the only source of drinking water, starting after weaning and continuing for 7 months, thus mimicking an intervention in current smokers. In the absence of berries, CS caused a loss of body weight, induced early cytogenetical damage in circulating erythrocytes and histopathological alterations in lung (emphysema, blood vessel proliferation, alveolar epithelial hyperplasia and adenomas), liver (parenchymal degeneration) and urinary bladder (epithelial hyperplasia). Both berry extracts inhibited the CS-related body weight loss, cytogenetical damage, liver degeneration, pulmonary emphysema and lung adenomas. Protective effects were more pronounced in female mice, which may be ascribed to modulation by berry components of the metabolism of estrogens implicated in lung carcinogenesis. Interestingly, both the carcinogen and the chemopreventive agents tested are complex mixtures that contain a multitude of components working through composite mechanisms.

Anthocyanins from purple sweet potato attenuate dimethylnitrosamine-induced liver injury in rats by inducing Nrf2-mediated antioxidant enzymes and reducing COX-2 and iNOS expression

Anthocyanins of the purple sweet potato exhibit antioxidant and hepatoprotective activities via a multitude of biochemical mechanisms. However, the signaling pathways involved in the actions of anthocyanin-induced antioxidant enzymes against chronic liver injury are not fully understood. We examined whether an anthocyanin fraction (AF) from purple sweet potato may prevent dimethylnitrosamine (DMN)-induced liver injury by inducing antioxidants via nuclear erythroid 2-related factor 2 (Nrf2) pathways and by reducing inflammation. Treatment with AF attenuated the DMN-induced increased serum alanine aminotransferase and aspartate aminotransferase activities. It also prevented the formation of hepatic malondialdehyde and the depletion of glutathione and maintained normal glutathione-S-transferase (GST) activity in the livers of DMN-intoxicated rats. Furthermore, AF increased the expression of Nrf2, NADPH:quinine oxidoreductase-1, heme oxygenase-1, and GSTα, which were reduced by DMN, and decreased the expression of cyclooxygenase-2 and inducible nitric oxide synthase. An increase in the nuclear translocation of nuclear factor kappa B (NF-κB) was observed in the DMN-induced liver injury group, but AF inhibited this translocation. Taken together, these results demonstrate that AF increases the expression of antioxidant enzymes and Nrf2 and at the same time decreases the expression of inflammatory mediators in DMN-induced liver injury. These data imply that AF induces antioxidant defense via the Nrf2 pathway and reduces inflammation via NF-κB inhibition.

Effects of blueberry on hepatic fibrosis and transcription factor Nrf2 in rats

AIM: To investigate the effects of blueberry on hepatic fibrosis and NF-E2-related factor 2 (Nrf2) transcription factor in rats.

METHODS: Forty-five male Sprague-Dawley rats were randomly divided into control group (A); CCl₄-induced hepatic fibrosis group (B); blueberry prevention group (C); Dan-shao-hua-xian capsule (DSHX) prevention group (D); and blueberry + DSHX prevention group (E). Liver fibrosis was induced in rats by subcutaneous injection of CCl₄ and a high-lipid/low-protein diet for 8 wk (except the control group). The level of hyaluronic acid (HA) and alanine aminotransferase (ALT) in serum was examined. The activity of superoxide dismutase (SOD), glutathione-S-transferase (GST) and malondialdehyde (MDA) in liver homogenates was determined. The degree of hepatic fibrosis was evaluated by hematoxylin and eosin and Masson staining. Expression of Nrf2 and NADPH quinone oxidoreductase 1 (Nqo1) was detected by real-time reversed transcribed-polymerase chain reaction, immunohistochemical techniques, and western blotting.

RESULTS: Compared with group B, liver indices, levels of serum HA and ALT of groups C, D and E were reduced (liver indices: 0.038 ± 0.008, 0.036 ± 0.007, 0.036 ± 0.005 vs 0.054 ± 0.009, P < 0.05; HA: 502.33 ± 110.57 ng/mL, 524.25 ± 255.42 ng/mL, 499.25 ± 198.10 ng/mL vs 828.50 ± 237.83 ng/mL, P < 0.05; ALT: 149.44 ± 16.51 U/L, 136.88 ± 10.07 U/L, 127.38 ± 11.03 U/L vs 203.25 ± 31.62 U/L, P < 0.05), and SOD level was significantly higher, but MDA level was lower, in liver homogenates (SOD: 1.36 ± 0.09 U/mg, 1.42 ± 0.13 U/mg, 1.50 ± 0.15 U/mg vs 1.08 ± 0.19 U/mg, P < 0.05; MDA: 0.294 ± 0.026 nmol/mg, 0.285 ± 0.025 nmol/mg, 0.284 ± 0.028 nmol/mg vs 0.335 ± 0.056 nmol/mg, P < 0.05). Meanwhile, the stage of hepatic fibrosis was significantly weakened (P < 0.05). Compared with group A, the activity of GST liver homogenates and expression levels of Nrf2 and Nqo1 in group B were elevated (P < 0.05). The expression level of Nrf2 and Nqo1 in groups C, D, and E were increased as compared with group B, but the difference was not significant.

CONCLUSION: Blueberry has preventive and protective effects on CCl₄-induced hepatic fibrosis by reducing hepatocyte injury and lipid peroxidation. However, these effects may not be related to the activation of Nrf2 during long-term of CCl₄.

Modeling relationships among active components in black raspberry (Rubus occidentalis L.) fruit extracts using high-resolution (1)H nuclear magnetic resonance (NMR) spectroscopy and multivariate statistical analysis

A process was developed to ascertain the bioactive components of black raspberry (Rubus occidentalis L.) fruit extracts by relating chemical constituents determined by high-field nuclear magnetic resonance (NMR) spectroscopy to biological responses using partial least-squares regression analysis. To validate our approach, we outlined relationships between phenolic signals in NMR spectra and chemical data for total monomeric anthocyanin (TMA) content and antioxidant capacity by the ferric-reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. Anthocyanins, cyanidin 3-O-rutinoside (Cy 3-rut), cyanidin 3-O-(2(G))-xylosylrutinoside (Cy 3-xylrut), and cyanidin 3-O-glucoside (Cy 3-glc), were significant contributors to the variability in assay results, with the two most important NMR bins corresponding to the methyl peaks in Cy 3-rut (6''') and/or Cy 3-xylrut (6(IV)). Many statistically important bins were common among assay models, but differences in structure-activity relationships resulted in changes in bin ranking. The specificity of these results supported the application of the process to investigate relationships among health-beneficial natural products and potential biological activity.

Effects of blueberry (Vaccinium ashei) on DNA damage, lipid peroxidation, and phase II enzyme activities in rats

Blueberry extracts have high antioxidant potential and increase phase II enzyme activities in vitro. This study tested the hypothesis that blueberries would reduce DNA damage and lipid peroxidation and increase phase II enzyme activities in vivo. Young, healthy male Sprague-Dawley rats (n = 8 per group) were fed control AIN-93 diets or AIN-93 diets supplemented with blueberries or blueberry extracts for 3 weeks. Diets were supplemented with 10% freeze-dried whole blueberries, blueberry polyphenol extract and sugars to match the 10% blueberry diet, or 1 and 0.2% blueberry flavonoids, which were primarily anthocyanins. Liver and colon mucosa glutathione-S-transferase (GST), quinone reductase, and UDP-glucuronosyltransferase activities in colon mucosa and liver were not significantly increased by freeze-dried whole blueberries or blueberry fractions. Liver GST activity, however, was approximately 25% higher than controls for the freeze-dried whole blueberry, blueberry polyphenol, and 1% flavonoid groups. DNA damage was significantly lower than control only in the liver of animals fed the 1% flavonoid diet. The level of urinary F(2)-isoprostanes, a measure of lipid peroxidation, was unaffected. In summary, in healthy rats, short-term supplementation with freeze-dried whole blueberries, blueberry polyphenols, or blueberry flavonoids did not significantly increase phase II enzyme activities. However, supplementation with 1% blueberry flavonoids did decrease oxidative DNA damage in the liver.

Carcinogen-altered genes in rat esophagus positively modulated to normal levels of expression by both black raspberries and phenylethyl isothiocyanate

Our recent study identified 2,261 dysregulated genes in the esophagi of rats that received a 1-week exposure to the carcinogen N-nitrosomethylbenzylamine (NMBA). We further reported that 1,323 of these genes were positively modulated to near-normal levels of expression in NMBA-treated animals that consumed dietary phenylethyl isothiocyanate (PEITC), a constituent of cruciferous vegetables. Herein, we report our results with companion animals that were fed a diet containing 5% freeze-dried black raspberries (BRB) instead of PEITC. We found that 462 of the 2,261 NMBA-dysregulated genes in rat esophagus were restored to near-normal levels of expression by BRB. Further, we have identified 53 NMBA-dysregulated genes that are positively modulated by both PEITC and BRB. These 53 common genes include genes involved in phase I and II metabolism, oxidative damage, and oncogenes and tumor suppressor genes that regulate apoptosis, cell cycling, and angiogenesis. Because both PEITC and BRB maintain near-normal levels of expression of these 53 genes, their dysregulation during the early phase of NMBA-induced esophageal cancer may be especially important in the genesis of the disease.

Bioactive food components and cancer risk reduction

Research over the last three decades has provided convincing evidence to support the premise that diets rich in fruits and vegetables may be protective against the risk of different types of cancers. Initial evidence for protective effect of fruits and vegetables against cancer risk came from population-based case-control studies, which prompted intense research aimed at (a) identification of bioactive component(s) responsible for the anticancer effects of fruits and vegetables, (b) elucidation of the mechanisms by which bioactive food components may prevent cancer, and (c) determination of their efficacy for prevention of cancer in animal models. The bioactive components responsible for cancer chemopreventive effects of various edible plants have now been identified. For instance, anticancer effect of Allium vegetables including garlic is attributed to organosulfur compounds (e.g., diallyl trisulfide). Interestingly, unlike cancer chemotherapy drugs, many bioactive food components selectively target cancer cells. Molecular basis for selectivity of anticancer bioactive food components towards cancer cells remains elusive, but these agents appear promiscuous and target multiple signal transduction pathways to inhibit cancer cell growth in vitro and in vivo. Despite convincing observational and experimental evidence, however, limited effort has been directed towards clinical investigations to determine efficacy of bioactive food components for prevention of human cancers. This article reviews current knowledge on cancer chemopreventive effects of a few highly promising dietary constituents, including garlic-derived organosulfides, berry compounds, and cruciferous vegetable-derived isothiocyanates, and serves to illustrate complexity of the signal transduction mechanisms in cancer chemoprevention by these promising bioactive food components.

Laboratory and clinical studies of cancer chemoprevention by antioxidants in berries

Reactive oxygen species (ROS) are a major cause of cellular injury in an increasing number of diseases, including cancer. Most ROS are created in the cell through normal cellular metabolism. They can be produced by environmental insults such as ultraviolet light and toxic chemicals, as well as by the inflammatory process. Interception of ROS or limiting their cellular effects is a major role of antioxidants. Due to their content of phenolic and flavonoid compounds, berries exhibit high antioxidant potential, exceeding that of many other foodstuffs. Through their ability to scavenge ROS and reduce oxidative DNA damage, stimulate antioxidant enzymes, inhibit carcinogen-induced DNA adduct formation and enhance DNA repair, berry compounds have been shown to inhibit mutagenesis and cancer initiation. Berry constituents also influence cellular processes associated with cancer progression including signaling pathways associated with cell proliferation, differentiation, apoptosis and angiogenesis. This review article summarizes laboratory and human studies, demonstrating the protective effects of berries and berry constituents on oxidative and other cellular processes leading to cancer development.

Chemoprevention of esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (SCC) is responsible for approximately one-sixth of all cancer-related mortality worldwide. This malignancy has a multifactorial etiology involving several environmental, dietary and genetic factors. Since esophageal cancer has often metastasized at the time of diagnosis, current treatment modalities offer poor survival and cure rates. Chemoprevention offers a viable alternative that could well be effective against the disease. Clinical investigations have shown that primary chemoprevention of this disease is feasible if potent inhibitory agents are identified. The Fischer 344 (F-344) rat model of esophageal SCC has been used extensively to investigate the biology of the disease, and to identify chemopreventive agents that could be useful in human trials. Multiple compounds that inhibit tumor initiation by esophageal carcinogens have been identified using this model. These include several isothiocyanates, diallyl sulfide and polyphenolic compounds. These compounds influence the metabolic activation of esophageal carcinogens resulting in reduced genetic (DNA) damage. Recently, a few agents have been shown to inhibit the progression of preneoplastic lesions in the rat esophagus into tumors. These agents include inhibitors of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), vascular endothelial growth factor (VEGF) and c-Jun [a component of activator protein-1 (AP-1)]. Using a food-based approach to cancer prevention, we have shown that freeze-dried berry preparations inhibit both the initiation and promotion/progression stages of esophageal SCC in F-344 rats. These observations have led to a clinical trial in China to evaluate the ability of freeze-dried strawberries to influence the progression of esophageal dysplasia to SCC.

Prevention and therapy of squamous cell carcinoma of the rodent esophagus using freeze-dried black raspberries

AIM

This study was conducted to determine if short-term treatment of Nnitrosomethylbenzylamine (NMBA)-induced tumors in the rat esophagus with dietary freeze-dried black raspberries (FBR) would result in tumor regression and enhanced survival of the animals.

METHODS

Four-week-old male Fisher-344 rats were administered an AIN-76A control diet and injected subcutaneously with 0.5 mg/kg NMBA once per week for 15 weeks. At 19 weeks, when rats had an average of 5-6 tumors (papillomas) per esophagus, they were given a control diet containing either 5%, 10%, or 20% FBR. After 7 weeks of berry treatment, all surviving rats were killed and tumor incidence, number and volume were determined.

RESULTS

Esophageal tumor incidences, numbers and volumes in NMBA-treated rats were not influenced by any of the berry treatments. There were progressive increases in the survival of NMBA-treated rats fed 5%-20% FBR diets; however, these increases were not significant.

CONCLUSION

FBR at 5%, 10%, and 20% of the diet had no effect on the development of NMBA-induced tumors in the rat esophagus or on animal survival when administered for 7 weeks beginning at the papilloma stage of tumor development. Thus, FBR appear to have no therapeutic value in the treatment of esophageal tumors. In contrast, dietary FBR are highly effective in preventing the development of NMBA-induced esophageal tumors in rats when administered before and during NMBA treatment or shortly after NMBA treatment when the esophagi contain preneoplastic (dysplastic) lesions of varying degrees of severity.

Effects of phenylethyl isothiocyanate on early molecular events in N-nitrosomethylbenzylamine-induced cytotoxicity in rat esophagus

There is little information on early molecular events in the development of N-nitrosomethylbenzylamine (NMBA)-induced rat esophageal tumorigenesis and of the effects of chemopreventive agents on these events. In this study, we identified genes in rat esophagus that were differentially expressed in response to short-term NMBA treatment and modulated by cotreatment with phenylethyl isothiocyanate (PEITC). Rats were fed AIN-76A diet or AIN-76A diet containing PEITC for 3 weeks. During the 3rd week of dietary treatment, they were administered three s.c. doses of NMBA (0.5 mg/kg body weight). Rats were sacrificed 24 h after the last treatment; esophagi were excised and processed for histologic grading, microarray and real-time PCR analysis. Histopathologic analysis showed that treatment of rats with PEITC had a protective effect on NMBA-induced preneoplastic lesions in the rat esophagus. We identified 2,261 genes that were differentially expressed in the NMBA-treated versus control esophagi and 1,936 genes in the PEITC + NMBA versus NMBA-treated esophagi. The intersection of these two sets resulted in the identification of 1,323 genes in NMBA-treated esophagus, the vast majority of which were modulated by PEITC to near-normal levels of expression. Measured changes in the expression levels of eight selected genes were validated using real-time PCR. Results from 12 microarrays indicated that PEITC treatment had a genome-wide modulating effect on NMBA-induced gene expression. Samples obtained from animals treated with PEITC alone or cotreated with PEITC + NMBA were more similar to controls than to samples treated with NMBA alone.

Protection against esophageal cancer in rodents with lyophilized berries: potential mechanisms

For several years, our laboratory has been evaluating the ability of lyophilized (freeze-dried) black raspberries (Rubus occidentalis, BRBs), blackberries (R. fructicosus, BBs), and strawberries (Fragaria ananasia, STRWs) to inhibit carcinogen-induced cancer in the rodent esophagus. To assure "standardized" berry preparations for study, each berry type is of the same cultivar, picked at about the same degree of ripeness, washed and frozen within 2-4 h of the time of picking, and freeze-dried under conditions that preserve the components in the berries. Some of the known chemopreventive agents in berries include vitamins A, C, and E and folic acid; calcium and selenium; beta-carotene, alpha-carotene, and lutein; polyphenols such as ellagic acid, ferulic acid, p-coumaric acid, quercetin, and several anthocyanins; and phytosterols such as beta-sitosterol, stigmasterol, and kaempferol. In initial bioassays, freeze-dried STRW, BRB, and BB powders were mixed into AIN-76A synthetic diet at concentrations of 5% and 10% and fed to Fischer 344 rats before, during, and after treatment with the esophageal carcinogen N-nitrosomethylbenzylamine (NMBA). At 25 wk of the bioassay, all three berry types were found to inhibit the number of esophageal tumors (papillomas) in NMBA-treated animals by 24-56% relative to NMBA controls. This inhibition correlated with reductions in the formation of the NMBA-induced O6-methylguanine adduct in esophageal DNA, suggesting that the berries influenced the metabolism of NMBA leading to reduced DNA damage. Studies are ongoing to determine the mechanisms by which berries influence NMBA metabolism and DNA adduct formation. BRBs and STRWs were also tested in a postinitiation scheme and were found to inhibit NMBA-induced esophageal tumorigenesis by 31-64% when administered in the diet following treatment of the animals with NMBA. Berries, therefore, inhibit tumor promotion and progression events as well as tumor initiation. In vivo mechanistic studies with BRBs indicate that they reduce the growth rate of premalignant esophageal cells, in part, through down-regulation of cyclooxygenase-2 leading to reduced prostaglandin production and of inducible nitric oxide synthase leading to reduced nitrate/nitrite levels in the esophagus. Based upon the preclinical data on rodents, we have initiated prevention trials in humans to determine if berries might exhibit chemopreventive effects in the esophagus.

Protection against esophageal cancer in rodents with lyophilized berries: potential mechanisms

For several years, our laboratory has been evaluating the ability of lyophilized (freeze-dried) black raspberries (Rubus occidentalis, BRBs), blackberries (R. fructicosus, BBs), and strawberries (Fragaria ananasia, STRWs) to inhibit carcinogen-induced cancer in the rodent esophagus. To assure "standardized" berry preparations for study, each berry type is of the same cultivar, picked at about the same degree of ripeness, washed and frozen within 2-4 h of the time of picking, and freeze-dried under conditions that preserve the components in the berries. Some of the known chemopreventive agents in berries include vitamins A, C, and E and folic acid; calcium and selenium; beta-carotene, alpha-carotene, and lutein; polyphenols such as ellagic acid, ferulic acid, p-coumaric acid, quercetin, and several anthocyanins; and phytosterols such as beta-sitosterol, stigmasterol, and kaempferol. In initial bioassays, freeze-dried STRW, BRB, and BB powders were mixed into AIN-76A synthetic diet at concentrations of 5% and 10% and fed to Fischer 344 rats before, during, and after treatment with the esophageal carcinogen N-nitrosomethylbenzylamine (NMBA). At 25 wk of the bioassay, all three berry types were found to inhibit the number of esophageal tumors (papillomas) in NMBA-treated animals by 24-56% relative to NMBA controls. This inhibition correlated with reductions in the formation of the NMBA-induced O6-methylguanine adduct in esophageal DNA, suggesting that the berries influenced the metabolism of NMBA leading to reduced DNA damage. Studies are ongoing to determine the mechanisms by which berries influence NMBA metabolism and DNA adduct formation. BRBs and STRWs were also tested in a postinitiation scheme and were found to inhibit NMBA-induced esophageal tumorigenesis by 31-64% when administered in the diet following treatment of the animals with NMBA. Berries, therefore, inhibit tumor promotion and progression events as well as tumor initiation. In vivo mechanistic studies with BRBs indicate that they reduce the growth rate of premalignant esophageal cells, in part, through down-regulation of cyclooxygenase-2 leading to reduced prostaglandin production and of inducible nitric oxide synthase leading to reduced nitrate/nitrite levels in the esophagus. Based upon the preclinical data on rodents, we have initiated prevention trials in humans to determine if berries might exhibit chemopreventive effects in the esophagus.