Expression of Metallothionein after Administration of Aspirin, Vitamin C or Zinc Supplement in the DMH Induced Colon Carcinoma in Rat

Background: Chemoprevention refers to the use of specificnatural or synthetic chemical agents to suppress the development and progression to carcinoma. The purpose of this study was to assess the effect of aspirin, vitamin C or zinc on the metallothionein (MT) mRNA gene expression as well as MT protein content byimmunohistochemistry andradioimmunoassay (RIA) in 1, 2-dimethyl hydrazine (DMH) induced cancerous colonic tissuein rats. Methods: Rats were randomly divided into three groups, group 1 (aspirin), group 2 (vitamin C) group 3 (zinc), each of which was further sub divided into two groups and given subcutaneous injections of DMH (30 mg/kg body weight) twice a week for 3 months and sacrificed at either 4 months (A-precancer model) or at 6 months (B-cancer model).The control groups were administered 0.5 ml saline subcutaneously. All the 3 groups were simultaneouslyadministered aspirin, vitamin Cor zinc supplement respectively from the beginning till the end of the study. Results: It was observed that rats co-treated with aspirin, vitamin C or zinc resulted in a significant increase in the colonic MT mRNA expression in the precancer and cancer model as compared to the saline only controls. MT protein expression showed a 60%, 64% and 78% immunopositivity in the co-treated groups respectively.The mean MT content in the precancer and the cancer model was restored to near normal levels in all the three co-treated groups. Conclusion: These results suggest that co-administration of aspirin, vitamin C or zinc resulted in a significant increase in MT mRNA gene expression, MT protein expression and MT protein content which could possibly be one of the reasons for a chemo protective effect against progression to colonic cancer in a chemically induced DMH model in rat.Zinc supplement had a greater effect on metallothionein expression than aspirin or vitamin C.

Effects of Dietary Resistant Starch on the Wnt Signaling Pathway and Preneoplastic Cells in the Colons of Azoxymethane-Treated Rats.

Dietary resistant starch (RS) has been suggested to reduce colonic neoplasia. To determine the effects of digestion-resistant cornstarch on colonic carcinogenesis and Wnt signaling in azoxymethane (AOM)-treated F344 rats, diets containing naturally occurring RS from corn lines derived partially from Guat209 (GUAT), AR16035 (AR), or a hybrid (ARxGUAT), containing 34.5 ± 2.0, 0.2 ± 0.1, and 1.9 ± 0.1% RS, respectively, were fed at 55% of the diet. GUAT-fed rats had increased cecal content and tissue weight and decreased cecal pH compared with AR- or ARxGUAT-fed rats. Numbers of aberrant crypt foci (ACF) were not different among diet groups. Increased numbers of crypts/focus were observed in AOM-injected rats fed GUAT compared with rats fed other diets. ß-catenin mRNA expression of the crypts was significantly increased in GUAT-fed rats injected with AOM relative to those injected with saline. These findings suggest that selected dietary RSs may at some level further enhance colonocyte proliferation and differentiation in an AOM-treated colon.

Red Wine and Pomegranate Extracts Suppress Cured Meat Promotion of Colonic Mucin-Depleted Foci in Carcinogen-Induced Rats.

Processed meat intake is carcinogenic to humans. We have shown that intake of a workshop-made cured meat with erythorbate promotes colon carcinogenesis in rats. We speculated that polyphenols could inhibit this effect by limitation of endogenous lipid peroxidation and nitrosation. Polyphenol-rich plant extracts were added to the workshop-made cured meat and given for 14 days to rats and 100 days to azoxymethane-induced rats to evaluate the inhibition of preneoplastic lesions. Colons of 100-d study were scored for precancerous lesions (mucin-depleted foci, MDF), and biochemical end points of peroxidation and nitrosation were measured in urinary and fecal samples. In comparison with cured meat-fed rats, dried red wine, pomegranate extract, α-tocopherol added at one dose to cured meat and withdrawal of erythorbate significantly decreased the number of MDF per colon (but white grape and rosemary extracts did not). This protection was associated with the full suppression of fecal excretion of nitrosyl iron, suggesting that this nitroso compound might be a promoter of carcinogenesis. At optimized concentrations, the incorporation of these plant extracts in cured meat might reduce the risk of colorectal cancer associated with processed meat consumption.

The role of natural polyphenols in cell signaling and cytoprotection against cancer development.

The cytoprotective and anticancer action of dietary in-taken natural polyphenols has for long been attributed only to their direct radical scavenging activities. Currently it is well supported that those compounds display a broad spectrum of biological and pharmacological outcomes mediated by their complex metabolism, interaction with gut microbiota as well as direct interactions of their metabolites with key cellular signaling proteins. The beneficial effects of natural polyphenols and their synthetic derivatives are extensively studied in context of cancer prophylaxis and therapy. Herein we focus on cell signaling to explain the beneficial role of polyphenols at the three stages of cancer development: we review the recent proceedings about the impact of polyphenols on the cytoprotective antioxidant response and their proapoptotic action at the premalignant stage, and finally we present data showing how phenolic acids (e.g., caffeic, chlorogenic acids) and flavonols (e.g., quercetin) hamper the development of metastatic cancer.

Flaxseed and its components differentially affect estrogen targets in pre-neoplastic hen ovaries.

Flaxseed has been studied for decades for its health benefits that include anti-cancer, cardio-protective, anti-diabetic, anti-inflammatory properties. The biologically active components that mediate these effects are the omega-3 fatty acids and the lignan, secoisolariciresinol diglucoside. We have previously shown that whole flaxseed supplemented diet decreases the severity and incidence of ovarian cancer while a 15% dose of flaxseed is most protective against inflammation and estrogen-induced chemical and genotoxicity. The objective of this study was to dissect the independent effects of the two flaxseed components on estrogen signaling and metabolism. Two and half year old hens were fed either a control diet, 15% whole flaxseed diet, defatted flax meal diet or 5% flax oil diet for 3 months after which the animals were sacrificed and blood and tissues were harvested. Whole flaxseed diet caused a decrease in expression of ERα. ERα target gene expression was assessed using RT(2) profiler PCR array. Some targets involved in the IGF/insulin signaling pathway (IRS1, IGFBP4, IGFBP5) were downregulated by flaxseed and its components. Flaxseed diet also downregulated AKT expression. A number of targets related to NF-kB signaling were altered by flaxseed diet including a series of targets implicated in cancer. Whole flaxseed diet also affected E2 metabolism by increasing CYP1A1 expression with a corresponding increase in the onco-protective E2 metabolite, 2-methoxyestradiol. The weak anti-estrogens, enterolactone, enterodiol and 2-methoxyestradiol, might be working synergistically to generate a protective effect on the ovaries from hens on whole flaxseed diet by altering the estrogen signaling and metabolism.

Lung cancer chemoprevention.

Lung cancer is the leading cause of cancer death in the United States, and the majority of diagnoses are made in former smokers. Although avoidance of tobacco abuse and smoking cessation clearly will have the greatest impact on lung cancer development, effective chemoprevention could prove to be more effective than treatment of established, advanced-stage disease. Chemoprevention is the use of dietary or pharmaceutical agents to reverse or block the carcinogenic process and has been successfully applied to common malignancies other than lung (including recent reports on the prevention of breast cancer in high-risk individuals). Despite previous studies in lung cancer chemoprevention failing to identify effective agents, our ability to define the highest-risk populations and the understanding of lung tumor and premalignant biology continue to make advances. Squamous cell carcinogenesis in the bronchial epithelium starts with normal epithelium and progresses through hyperplasia, metaplasia, dysplasia, and carcinoma in situ to invasive cancer. Precursor lesions also have been identified for adenocarcinoma, and these premalignant lesions are targeted by chemopreventive agents in current and future trials. Chemopreventive agents can currently only be recommended as part of well-designed clinical trials, and multiple trials have recently been completed or are enrolling subjects.

Egg yolk proteins suppress azoxymethane-induced aberrant crypt foci formation and cell proliferation in the colon of rats.

Dietary proteins can influence colonic carcinogenesis; some proteins have a promotional effect, whereas others exhibit a preventive effect. Dietary egg yolk proteins have been reported to suppress the expression of colon tumors in rats. In this study, we investigated the effect of consumption egg yolk proteins on cell proliferation in a rat model of azoxymethane (AOM)-induced colon cancer. We hypothesize, based on the literature of egg yolk protein actions, that they protect against colon tumor development. Therefore, male F344 rats were fed a purified AIN-93G diet containing either 20% casein (control) or 20% egg yolk proteins for 5 weeks. After 1 week on the experimental diet, the rats were administered weekly subcutaneous injections of saline or AOM for 2 weeks to induce aberrant crypt foci. Rats were administered an intraperitoneal injection of 5-bromo-2'-deoxyuridine 1 hour before being euthanized for examination of DNA synthesis in the colonic mucosa. The contents of the cecum were analyzed for the presence of short-chain fatty acids (SCFAs). In the AOM-injected rats, the yolk protein diet suppressed aberrant crypt foci formation and reduced the proliferative 5-bromo-2'-deoxyuridine-labeling index in the proximal colon when compared with the control diet. A significant increase in cecal SCFAs was observed in the rats that were fed egg yolk proteins. These results indicate that dietary egg yolk proteins have a preventive effect on AOM-induced large bowel carcinogenesis in rats; it exerts this effect by altering cell proliferation through SCFA production. This study suggests that the consumption of egg yolk proteins might be protective against colon carcinogenesis.

Inflammation-associated serum and colon markers as indicators of dietary attenuation of colon carcinogenesis in ob/ob mice.

Although inflammatory cytokines and obesity-associated serum proteins have been reported as biomarkers of colorectal adenoma risk in humans, little is known of biomarkers of response to interventions that attenuate tumorigenesis. Dietary navy beans and their fractions attenuate colon carcinogenesis in carcinogen-induced genetically obese mice. We hypothesized that this attenuation would be associated with changes in inflammatory cytokines and obesity-related serum proteins that may serve as measures of efficacy. ob/ob mice (n = 160) were injected with the carcinogen azoxymethane (AOM) to induce colon cancer and randomly placed on one of four diets (control, whole navy bean, bean residue fraction, or bean extract fraction) for 26 to 28 wk. Serum was analyzed for 14 inflammation- or obesity-related proteins, and colon RNA was analyzed for expression of 84 inflammation-associated genes. Six of 14 serum proteins were increased [i.e., interleukin (IL)-4, IL-5, IL-6, IL-10, IFN gamma, granulocyte macrophage colony-stimulating factor] in hyperplastic/dysplastic stages of colon carcinogenesis. Bean-fed mice had significantly higher monocyte chemoattractant protein-1 and lower IL-6 levels in serum. In colon mucosa, 55 of 84 inflammation-associated genes differed between AOM-induced and noninduced mice. Of the 55 AOM-induced genes, 5 were counteracted by bean diets, including IL-6 whose increase in expression levels was attenuated by bean diets in AOM-induced mice. In summary, IL-6 emerged as a serum protein that was increased in hyperplastic/dysplastic stages of colon carcinogenesis, but attenuated with bean-based diet in serum and colon mucosa. Changes in a subset of inflammation-associated serum proteins and colon gene expression may serve as response indicators of dietary attenuation of colon carcinogenesis.

Nutritional interventions and outcome in patients with cancer or preinvasive lesions: systematic review.

BACKGROUND: Dietary modifications and supplements are used widely by patients with cancer and preinvasive lesions as an adjunct to standard treatment. Given the widespread use of nutritional modifications and supplements by such patients and concerns about the lack of benefit and possible harm, we conducted a systematic review of randomized controlled trials to examine the effect of nutritional interventions on patients with cancer or preinvasive lesions. METHODS: We searched electronic databases and reference lists to locate all eligible trials and analyzed trial quality. Outcome measures were all-cause and cancer mortality, disease-free survival, cancer recurrence, second primary cancer, recurrence of a preinvasive lesion, or progression to cancer. Results of individual trials were combined by use of random-effects meta-analyses. RESULTS: We identified 59 eligible trials, 25 in patients with cancer and 34 in patients with preinvasive lesions, respectively. Trial quality was generally low; only three trials (two of cancer and one of preinvasive lesions) had adequate methods for generating the allocation sequence, allocation concealment, and masking both outcome assessors and participants. The combined odds ratio (OR) for the effect of a healthy diet-given alone or with dietary supplements, weight loss, or exercise-on all-cause mortality was 0.90 (95% confidence interval [CI] = 0.46 to 1.77). There was no evidence of an association between the use of antioxidant (OR = 1.01, 95% CI = 0.88 to 1.15) or retinol (OR = 0.97, 95% CI = 0.83 to 1.13) supplements and all-cause mortality. Meta-analyses of all other outcomes did not show clear evidence of benefit or harm. CONCLUSIONS: The impact of most nutritional interventions cannot be reliably estimated because of the limited number of trials, many of which were of low quality. There is no evidence that dietary modification by cancer patients improves survival and benefits disease prognosis.

Inulin-type fructans and reduction in colon cancer risk: review of experimental and human data.

Inulin-type fructans (beta(2,1)fructans) extracted from chicory roots (Cichorium intybus) are prebiotic food ingredients, which in the gut lumen are fermented to lactic acid and SCFA. Research in experimental animal models revealed that inulin-type fructans have anticarcinogenic properties. A number of studies report the effects of inulin-type fructans on chemically induced pre-neoplastic lesions (ACF) or tumours in the colon of rats and mice. In twelve studies, there were twenty-nine individual treatment groups of which twenty-four measured aberrant crypt foci (ACF) and five measured tumours. There was a significant reduction of ACF in twenty-one of the twenty-four treatment groups and of tumour incidence in five of the five treatment groups. Higher beneficial effects were achieved by synbiotics (mixtures of probiotics and prebiotics), long-chain inulin-type fructans compared to short-chain derivatives, and feeding high-fat Western style diets. Inulin-type fructans reduced tumour incidence in APC(Min) mice in two of four studies and reduced growth and metastasising properties of implanted tumour cells in mice (four studies). The effects have been reported to be associated with gut flora-mediated fermentation and production of butyrate. In human cells, inulin-derived fermentation products inhibited cell growth, modulated differentiation and reduced metastasis activities. In conclusion, evidence has been accumulated that shows that inulin-type fructans and corresponding fermentation products reduced the risks for colon cancer. The involved mechanisms included the reduction of exposure to risk factors and suppression of tumour cell survival. Thus, this specific type of dietary fibre exerted both blocking agent and suppressing agent types of chemopreventive activities.

Tomato and garlic can modulate azoxymethane-induced colon carcinogenesis in rats.

Tomato (Lycopersicon esculentum) and garlic (Allium cepa) are important constituents of the human diet. Compounds like diallyl sulfides, diallyl disulfides and quercetin, which are active components of garlic, have known anti-inflammatory, antimutagenic activities. Similarly, active components in tomato, such as kaempferol and chlorogenic acid, have antimutagenic activities and lycopene is the most active oxygen quencher with potential chemopreventive activities. In view of this, an endeavour was made to evaluate the anticarcinogenic effect, if any, of tomato and garlic consumption individually and in combination on azoxymethane-induced colonic precancerous lesion, the aberrant crypt foci in animal model. Sprague-Dawley rats (4-5 weeks old) were injected with azoxymethane (15 mg/kg b.w.) and orally administered with 2% (w/v) of tomato, garlic and a combination of both. After 12 weeks of first azoxymethane injection, colons were assessed for aberrant crypt foci and compared with the carcinogen control group. Lipid peroxidation level and glutathione-S-transferase (GST) activity were assessed in liver as well as in colon. Furthermore, in situ cell proliferation and apoptosis were estimated using the Brdu incorporation method and TUNEL method respectively. It was observed that aberrant crypt foci were reduced in all treated groups (by 32.11% in garlic, by 76.14% in tomato and by 55.96% in the combination group). Among treated groups, GST activity was found to be induced in both liver and colon, whereas considerable reduction in lipid peroxidation level was observed in liver as well as in colon with respect to the carcinogen control group. Significant reduction in Brdu labelling index and increase in apoptotic index in colon was noted in the treated groups. These results suggest that tomato and garlic suspensions have a protective effect on colon carcinogenesis, which is mediated by modulation of different biological pathways during carcinogenesis.

Prevention by long-term fermented miso of induction of colonic aberrant crypt foci by azoxymethane in F344 rats.

The present study was designed to investigate the effects of fermented miso in the diet on the induction of aberrant crypt foci (ACF) by azoxymethane (AOM) in male F344 rats. A total of 50 rats, 8 weeks of age, were divided into 5 groups and given weekly subcutaneous injections of AOM (15 mg/kg body wt) for 3 weeks. Rats were fed a normal control MF solid diet, or solid diet containing 10% long-term fermented (aged), medium- or short-term fermented miso, or 2.2% NaCl for 5 weeks, starting one week before the first AOM dosing. It was found that, compared to the control (MF) diet, the long-term fermented diet significantly decreased (by 22.2%) ACF/colon, but increased (by 18.2%) the number of aberrant crypts (Acs)/focus. The latter was also increased by the medium-term fermented diet (by 25.3%). The PCNA labeling index was only affected by the short-term fermented diet (36.9% increase) and by 2.2% NaCl diet (27.2% increased). The present results indicate that aged or completely fermented miso supplemented into the diet, could act as a chemopreventive agent for colon carcinogenesis.

High vegetable and fruit diet intervention in premenopausal women with cervical intraepithelial neoplasia.

OBJECTIVE: To examine whether diet intervention can promote increased vegetable and fruit intake, as reflected in increased plasma carotenoid and decreased plasma total homocysteine concentrations, in premenopausal women with cervical intraepithelial neoplasia, a precancerous condition. DESIGN: Randomized controlled diet intervention study. SUBJECTS: Fifty-three free-living premenopausal women who had been diagnosed with cervical intraepithelial neoplasia, were randomly assigned to an intervention (n = 27) or a control (n = 26) group. INTERVENTION: Individualized dietary counseling to increase vegetable and fruit intake. MAIN OUTCOME MEASURES: Diet was assessed by food frequency questionnaire. Plasma carotenoids and total homocysteine were measured at enrollment and at 6 months follow up. ANALYSIS: Associations between baseline plasma concentrations of carotenoids and homocysteine and influencing factors were examined with multiple regression analysis. Repeated measures analysis of variance was used to test for group by time effects in these plasma concentrations. Plasma carotenoids at baseline and 6 months in the study groups, and differences in homocysteine concentrations from baseline to 6 months, were compared with independent sample t tests. RESULTS: Repeated measures analysis of variance showed significant group by time effects (P<.01) in plasma carotenoid and homocysteine concentrations. In the intervention group, total plasma carotenoids increased by an average of 91%, from 2.04+/-0.13 (mean+/-standard error of the mean) to 3.90+/-0.56 micromol/L and plasma total homocysteine was reduced by 11%, from 9.01+/-0.40 to 8.10+/-0.44 micromol/L (P<.003). Neither changed significantly in the control group. APPLICATIONS: Individualized dietary counseling can effectively promote increased vegetable and fruit intake in premenopausal women. This dietary pattern may reduce risk for cancer and other chronic diseases and also promote an improvement in folate status.

Effect of branched-chain amino acids on the composition and cytolytic activity of liver-associated lymphocytes in rats.

BACKGROUND: Although branched-chain aminoacids (BCAA) are reported to be effective in prolongation of the mean survival time of patients with liver cirrhosis, it is not clear whether BCAA could influence the immune function in those patients. METHODS: Branched-chain amino acids were given as a supplement to carbon tetrachloride-induced cirrhotic rats, and an aminogram of the liver and kinetics of liver-associated lymphocytes (LAL) were then analysed. RESULTS: Liver cirrhosis was established at the 12th week, and glutathione S-transferase placental form (GST-P)-positive lesions, which are known to be pre-neoplastic lesions, occupied 1.72+/-0.84% of the liver at the 16th week in the controls. At this time the LAL showed an increase in the number of CD5-, CD8- and CD18-positive cells and augmentation of lectin-dependent cellular cytotoxicity (LDCC) activity. Furthermore, supplementation of BCAA increased the number of LAL, especially CD8-positive cells and natural killer cells, and augmented LDCC activity of LAL at the 16th week. The number of LAL was positively correlated with the valine concentration in the plasma and liver, and the area of GST-P-positive lesions tended to be decreased in the BCAA group. CONCLUSION: These findings suggest that BCAA administration has stimulatory effects on the local immune systems of the liver, which may have a potential to inhibit hepatocarcinogenesis. Moreover, among all amino acids valine might be an important amino acid for enhancing the immune function of LAL.

Modifying effect of tuna orbital oil rich in docosahexaenoic acid and vitamin D3 on azoxymethane-induced colonic aberrant crypt foci in rats.

The modifying effect of dietary tuna (Thunnus thynnus orientalis) orbital oil rich in docosahexaenoic acid (DHA) and vitamin D3 (VD3) on the development of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) was investigated in male F344 rats. Animals were given three weekly subcutaneous injections of AOM (15 mg/kg body weight) to induce ACF. The rats were fed the experimental diet containing 5% tuna orbital oil (low fish oil), 23.5% tuna orbital oil (high fish oil), 5% corn oil (low corn oil) or 23.5% corn oil (high corn oil) for 5 weeks, starting 1 week before the first dose of AOM. Animals were sacrificed 2 weeks after the last AOM injection to count colonic ACF and assay the expression of cyclooxygenase (COX)-1 and -2. High corn oil diet significantly increased the development of ACF, when compared with low corn oil diet (P<0.005). High fish oil diet also increased ACF formation compared with low fish oil diet (P<0.01), but the increase was smaller than high corn oil diet. The frequency of ACF was significantly lower in the rats fed high fish oil diet than high corn oil diet (P<0.02). Moreover, frequency of ACF consisted of 4 or more crypts in rats fed the high fish oil diet was significantly lower than that of rats given high corn oil diet. COX-1 and COX-2 expression did not significantly differ among the groups. These results suggest that fish oil derived from tuna, which contains high amounts of DHA and VD3, suppresses the formation and growth of ACF without affecting COX-1 and COX-2 expression, and may have a preventive effect on colon carcinogenesis.

Dietary restriction reduces insulin-like growth factor I levels, which modulates apoptosis, cell proliferation, and tumor progression in p53-deficient mice.

Diet contributes to over one-third of cancer deaths in the Western world, yet the factors in the diet that influence cancer are not elucidated. A reduction in caloric intake dramatically slows cancer progression in rodents, and this may be a major contribution to dietary effects on cancer. Insulin-like growth factor I (IGF-I) is lowered during dietary restriction (DR) in both humans and rats. Because IGF-I modulates cell proliferation, apoptosis, and tumorigenesis, the mechanisms behind the protective effects of DR may depend on the reduction of this multifaceted growth factor. To test this hypothesis, IGF-I was restored during DR to ascertain if lowering of IGF-I was central to slowing bladder cancer progression during DR. Heterozygous p53-deficient mice received a bladder carcinogen, p-cresidine, to induce preneoplasia. After confirmation of bladder urothelial preneoplasia, the mice were divided into three groups: (a) ad libitum; (b) 20% DR; and (c) 20% DR plus IGF-I (IGF-I/DR). Serum IGF-I was lowered 24% by DR but was completely restored in the IGF-I/DR-treated mice using recombinant IGF-I administered via osmotic minipumps. Although tumor progression was decreased by DR, restoration of IGF-I serum levels in DR-treated mice increased the stage of the cancers. Furthermore, IGF-I modulated tumor progression independent of changes in body weight. Rates of apoptosis in the preneoplastic lesions were 10 times higher in DR-treated mice compared to those in IGF/DR- and ad libitum-treated mice. Administration of IGF-I to DR-treated mice also stimulated cell proliferation 6-fold in hyperplastic foci. In conclusion, DR lowered IGF-I levels, thereby favoring apoptosis over cell proliferation and ultimately slowing tumor progression. This is the first mechanistic study demonstrating that IGF-I supplementation abrogates the protective effect of DR on neoplastic progression.

Dietary lycopene decreases the initiation of liver preneoplastic foci by diethylnitrosamine in the rat.

To test whether carotenoids can modulate the initiation of liver preneoplasia by diethylnitrosamine (DEN) or by 2-nitropropane (2-NP) in a sequential protocol of hepatocarcinogenesis, male weanling rats were fed for three or four weeks (respectively) diets containing beta-carotene, canthaxanthin, astaxanthin, or lycopene (300 mg/kg diet) or an excess of vitamin A (15,000 retinol equivalents/kg diet) or were treated intraperitoneally with 3-methylcholanthrene. During this period, all rats were injected intraperitoneally with the initiator carcinogen, either 2-NP (6 times at 100 mg/kg body wt) or DEN (once at 100 mg/kg body wt). Three weeks after the termination of carotenoid or vitamin A feeding, the rats received 50 ppm of 2-acetylaminofluorene in their diet for a two-week period, in the middle of which they were subjected to two-thirds partial hepatectomy, and were sacrificed one week later. gamma-Glutamyl transpeptidase- and placental glutathione S-transferase-positive foci were detected in frozen-cut liver sections by histochemical and histoimmunochemical techniques, respectively. None of the treatments tested had any influence on the number and size of preneoplastic liver foci induced by 2-NP, despite a significant incorporation and persistence in the liver of the carotenoids, except astaxanthin, and of supplemental vitamin A. Feeding the rats lycopene significantly decreased the size of gamma-glutamyl transpeptidase- and glutathione S-transferase-positive foci induced by DEN (by 64% and 65%, respectively), as well as the fraction of liver volume occupied by foci (by 84% and 79%, respectively), but did not significantly reduce their number. The other carotenoids, including beta-carotene, exerted no significant effects on DEN-induced preneoplasias. Lycopene does not appear to act through its antioxidant properties, but rather through its modulating effect on the liver enzyme activating DEN, cytochrome P-450 2E1.

Inability of low- or high-fat diet to modulate late stages of colon carcinogenesis in Sprague-Dawley rats.

The main objective of the present proposal was to investigate the effect of feeding a low- or high-fat diet in the early and late stages of colon carcinogenesis. Sprague-Dawley male rats were injected with azoxymethane (20 mg/kg/week) for 2 weeks. One week later they were randomly allocated to eat a low-fat (4% beef tallow + 1% corn oil) or a high-fat (18.6% beef tallow + 4.7% corn oil) diet (LF or HF). After 10 weeks of feeding, 10 animals per group were killed, and their colons were evaluated for tumors. The remaining animals in each group were divided further into LF and HF groups. The four experimental groups consisted of groups receiving LF or HF diet throughout the study (LF-LF or HF-HF) and the groups fed LF or HF diet for the first 10 weeks, then assigned the alternate diet for the remainder of the duration (LF-HF or HF-LF). By week 26, the remaining animals were killed, and their colons were evaluated for the number, location and size of tumors. The tumor incidence in the HF-HF and HF-LF groups were higher than the LF-LF and LF-HF groups (81.6 and 84.8% versus 71.4 and 60.0%). Tumor multiplicity ranged from 1.86 +/- 0.26 to 2.54 +/- 0.33 in all groups. The average size of tumors and total tumor area/rat were affected significantly by the time at which the diet was fed. Average size and total tumor area in the animals fed HF diet during early stages (HF-HF and HF-LF) were significantly higher than those fed the LF diet during the early stages. Late intervention by specific diets did not affect tumor outcome. Sequential enumeration of aberrant crypt foci of different growth features representing early preneoplastic stages corroborated the findings of the tumor outcome. It was concluded that early preneoplastic stages were more sensitive than their advanced counterparts to the dietary interventions of the present study.

The polyp prevention trial I: rationale, design, recruitment, and baseline participant characteristics.

The Polyp Prevention Trial (PPT) is a multicenter randomized controlled trial examining the effect of a low-fat (20% of total energy intake), high-fiber (18 g/1000 kcal), high-vegetable and -fruit (5-8 daily servings) dietary pattern on the recurrence of adenomatous polyps of the large bowel, precursors of most colorectal malignancies. Eligibility criteria include one or more adenomas removed within 6 months of randomization; complete nonsurgical polyp removal and complete colonic examination to the cecum at the qualifying colonoscopy: age 35 years of more; no history of colorectal cancer, inflammatory bowel disease, or large bowel resection; and satisfactory completion of a food frequency questionnaire and 4-day food record. Of approximately 38,277 potential participants with one or more polyps recently resected, investigators at eight clinical centers randomized 2,079 (5.4%; 1,037 in the intervention and 1,042 in the control arm) between June 1991 and January 1994, making the PPT the largest adenoma recurrence trial ever conducted. Of PPT participants, 35% are women and 10% are minorities. At study entry, participants averaged 61.4 years of age; 14% of them smoked, and 22% used aspirin. At the baseline colonoscopy, 35% of participants had two or more adenomas, and 29% had at least one large (> of = 1 cm) adenoma. Demographic, behavioral, dietary, and clinical characteristics are comparable across the two study arms. Participants have repeat colonoscopies after 1 (T(1)) and 4 (T(4)) years of follow-up. The primary end point is adenoma recurrence; secondary end points include number, size, location, and histology of adenomas. All resected lesions are reviewed centrally by gastrointestinal pathologists. The trial provides 90% power to detect a reduction of 24% in the annual adenoma recurrence rate. The primary analytic period, on which sample size calculations were based is 3 years (T(1) to T(4)), which permits a 1-year lag time for the intervention to work and allows a more definitive clearing of lesions at T(1), given that at least 10-15% of polyps may be missed at baseline. The final (T(4)) colonoscopies are expected to be completed in early 1998.