Nutrition and its relationship to cancer

Food-Borne Chemical Carcinogens and the Evidence for Human Cancer Risk

Commonly consumed foods and beverages can contain chemicals with reported carcinogenic activity in rodent models. Moreover, exposures to some of these substances have been associated with increased cancer risks in humans. Food-borne carcinogens span a range of chemical classes and can arise from natural or anthropogenic sources, as well as form endogenously. Important considerations include the mechanism(s) of action (MoA), their relevance to human biology, and the level of exposure in diet. The MoAs of carcinogens have been classified as either DNA-reactive (genotoxic), involving covalent reaction with nuclear DNA, or epigenetic, involving molecular and cellular effects other than DNA reactivity. Carcinogens are generally present in food at low levels, resulting in low daily intakes, although there are some exceptions. Carcinogens of the DNA-reactive type produce effects at lower dosages than epigenetic carcinogens. Several food-related DNA-reactive carcinogens, including aflatoxins, aristolochic acid, benzene, benzo[a]pyrene and ethylene oxide, are recognized by the International Agency for Research on Cancer (IARC) as causes of human cancer. Of the epigenetic type, the only carcinogen considered to be associated with increased cancer in humans, although not from low-level food exposure, is dioxin (TCDD). Thus, DNA-reactive carcinogens in food represent a much greater risk than epigenetic carcinogens.

Mechanisms of DNA-reactive and epigenetic chemical carcinogens: applications to carcinogenicity testing and risk assessment

Chemicals with carcinogenic activity in either animals or humans produce increases in neoplasia through diverse mechanisms. One mechanism is reaction with nuclear DNA. Other mechanisms consist of epigenetic effects involving either modifications of regulatory macromolecules or perturbation of cellular regulatory processes. The basis for distinguishing between carcinogens that have either DNA reactivity or an epigenetic activity as their primary mechanism of action is detailed in this review. In addition, important applications of information on these mechanisms of action to carcinogenicity testing and human risk assessment are discussed.

Synthesis of bis-indolylmethanes as new potential inhibitors of β-glucuronidase and their molecular docking studies

Thirty-two (32) bis-indolylmethane-hydrazone hybrids 1-32 were synthesized and characterized by ¹HNMR, ¹³CNNMR and HREI-MS. All compounds were evaluated in vitro for β-glucuronidase inhibitory potential. All analogs showed varying degree of β-glucuronidase inhibitory potential ranging from 0.10 ± 0.01 to 48.50 ± 1.10 μM when compared with the standard drug d-saccharic acid-1,4-lactone (IC₅₀ value 48.30 ± 1.20 μM). Derivatives 1-32 showed the highest β-glucuronidase inhibitory potentials which is many folds better than the standard drug d-saccharic acid-1,4-lactone. Further molecular docking study validated the experimental results. It was proposed that bis-indolylmethane may interact with some amino acid residues located within the active site of β-glucuronidase enzyme. This study has culminated in the identification of a new class of potent β-glucuronidase inhibitors.

Changing Food Selections in a Public Cafeteria

The current study evaluated the influence of three behavioral procedures on the eating behavior of lunch-time patrons in a university cafeteria. A total of 5542 observations were made over a 16-month period. Food selections were unobtrusively recorded as the subjects passed through the checkout lines. A determination of sex/weight class was also made (male/female lean, normal, or obese). Using a series of reversal (ABA) designs, the subjects were exposed to the following procedures: Caloric feedback prior to food selection; labeled items to indicate nutritionally favorable choices; and a token system in which a cash rebate was made contingent on appropriate food selection behavior. The results showed that the token system produced the most uniform increases in vegetables, soup, fruit, chicken, fish, turkey, and salad consumption, while consumption of high-fat and dessert items was reduced. Caloric feedback was associated with decreased carbohydrate, red meat, and dairy product consumption, with little increase in other areas. Labeling had isolated effects on obese subjects' vegetable, soup, and fruit consumption. Female obese were found to be the most sensitive to all the procedures, and male obese the most resistant. Implications for the treatment of obesity and self-regulation of eating behavior are discussed.

Lessons learned from cancer prevention studies with nutrients and non-nutritive dietary constituents

Epidemiological studies have observed the association between dietary patterns and the risk of certain types of cancer. Extensive studies have been conducted on the cancer preventive activities of constituents from food and beverages. While laboratory research has shown impressive and promising results, such promising cancer preventive activities have not been demonstrated in many human intervention trials. This article analyzes the major differences between these different types of studies and the limitations of these studies. Animal and cell line studies usually use optimal conditions in order to demonstrate the hypothesized effects, sometimes without considering the human relevance. On the other hand, some clinical trials were designed without a good understanding of the biochemical and pharmacological properties of the agents used. Lessons learned from these studies will be illustrated using vitamin E, β-carotene and selenium as examples for nutrients, and green tea polyphenols as an example for non-nutritive dietary constituents. From the lessons learned, we believe that more interdisciplinary collaboration and integration of laboratory and human studies would effectively advance the field of cancer prevention.

Algal sulfated carrageenan inhibits proliferation of MDA-MB-231 cells via apoptosis regulatory genes

Marine algae are prolific sources of sulfated polysaccharides, which may explain the low incidence of certain cancers in countries that traditionally consume marine food. Breast cancer is one of the most common types of non‑skin cancer in females. In this study, extracted sulfated carrageenan (ESC), predominantly consisting of ι‑carrageenan extracted from the red alga Laurencia papillosa, was characterized using Fourier transform infrared spectrometry. The biological effects of the identified extract were investigated and its potential cytotoxic activity was tested against the MDA‑MB‑231 cancer cell line. The biological biometer of the inhibitory concentration of the polysaccharide‑treated MDA‑MB‑231 cells was determined as 50 µM. Treatment with 50 µM ESC inhibited cell proliferation and promptly induced cell death through nuclear condensation and DNA fragmentation. Characterization of polysaccharide‑treated MDA‑MB‑231 cell death revealed that induction of apoptosis occurred via the activation of the extrinsic apoptotic caspase‑8 gene. The apoptotic signaling pathway was regulated through caspase‑3, caspase‑9, p53, Bax and Bcl‑2 genes. These findings suggest that ESC may serve as a potential therapeutic agent to target breast cancer via prompting apoptosis.

The consumption of seaweed as a protective factor in the etiology of breast cancer: proof of principle

Daily consumption of seaweed has been proposed as a factor in explaining lower postmenopausal breast cancer (BC) incidence and mortality rates in Japan. This clinical trial assessed the impact of introducing seaweed- to non-seaweed-consuming American postmenopausal women. Fifteen healthy postmenopausal women were recruited for a 3-month single-blinded placebo controlled clinical trial; five had no history of BC (controls) and ten were BC survivors. Participants ingested ten capsules daily (5 g day-1) of placebo for 4 weeks, seaweed (Undaria) for 4 weeks, then placebo for another 4 weeks. Blood and urine samples were collected after each treatment period. Urinary human urokinase-type plasminogen activator receptor concentrations (uPAR) were analyzed by ELISA, and urine and serum were analyzed for protein expression using surface-enhanced laser desorption/ionization-time-of-flight mass spectrometry (SELDI-TOF-MS). Urinary creatinine standardized uPAR (in pg mL μg-1 creatinine) changed significantly between groups, decreasing by about half following seaweed supplementation (placebo 1, 1.5 (95 % CI, 0.9-2.1) and seaweed, 0.9 (95 % CI, 0.6-1.1) while placebo 2 returned to pre-seaweed concentration (1.7 (95 % CI, 1.2-2.2); p = 0.01, ANOVA). One SELDI-TOF-MS-identified urinary protein (m/z 9,776) showed a similar reversible decrease with seaweed and is reported to be associated with cell attachment. One serum protein (m/z 8,928) reversibly increased with seaweed and may be the immunostimulatory complement activation C3a des-arginine. uPAR is higher among postmenopausal women generally, and for BC patients, it is associated with unfavorable BC prognosis. By lowering uPAR, dietary seaweed may help explain lower BC incidence and mortality among postmenopausal women in Japan.

Omega-3 Fatty Acids and PPARgamma in Cancer

Omega-3 (or n-3) polyunsaturated fatty acids (PUFAs) and their metabolites are natural ligands for peroxisome proliferator receptor activator (PPAR)gamma and, due to the effects of PPARgamma on cell proliferation, survival, and differentiation, are potential anticancer agents. Dietary intake of omega-3 PUFAs has been associated with a reduced risk of certain cancers in human populations and in animal models. In vitro studies have shown that omega-3 PUFAs inhibit cell proliferation and induce apoptosis in cancer cells through various pathways but one of which involves PPARgamma activation. The differential activation of PPARgamma and PPARgamma-regulated genes by specific dietary fatty acids may be central to their distinct roles in cancer. This review summarizes studies relating PUFAs to PPARgamma and cancer and offers a new paradigm relating an n-3 PUFA through PPARgamma to the expression of the cell surface proteoglycan, syndecan-1, and to the death of cancer cells.

Endogenous synthesis of n-3 polyunsaturated fatty acids in Fat-1 mice is associated with increased mammary gland and liver syndecan-1

Long chain n-3 PUFA have been shown to have chemopreventive properties against breast cancer through various mechanisms. One pathway, studied in human breast cancer cell lines, involves upregulation of the proteoglycan, syndecan-1 (SDC-1) by n-3 PUFA-enriched LDL. Using Fat-1 mice that are able to convert n-6 to n-3 PUFA, we tested whether SDC-1 level in vivo is elevated in mammary glands due to endogenously synthesized rather than LDL-derived n-3 PUFA. Female Fat-1 and wild type (wt) mice were fed an n-6 PUFA- enriched diet for 7 weeks. Fatty acid analysis of plasma lipoproteins showed that total n-6 PUFA reflected dietary intake similarly in both genotypes (VLDL, 36.2±2.2 and 40.9±3.9; LDL, 49.0±3.3 and 48.1±2.0; HDL, 54.6±1.2 and 58.2±1.3, mean ± SEM percent of total fatty acids for Fat-1 and wt animals respectively). Lipoprotein percent n-3 PUFA was also similar between groups. However, phospholipids and triglycerides extracted from mammary and liver tissues demonstrated significantly higher n-3 PUFA and a corresponding decrease in the ratio n-6/n-3 PUFA in Fat-1 compared to wt mice. This was accompanied by higher SDC-1 in mammary glands and livers of Fat-1 mice, thus demonstrating that endogenously synthesized n-3 PUFA may upregulate SDC-1 in the presence of high dietary n-6 PUFA.

Tumorigenesis of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), but not enhancing effects of concomitant high-fat diet, on lung carcinogenesis in female A/J mice

It has been reported that 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) induces liver tumors and to a lesser extent lung lesions, lymphomas and leukemias in CDF(1) mice. Since a number of case control studies have pointed to a positive association between fat consumption and lung cancer, we examined the lung carcinogenic potential of MeIQx treatment concomitant with a high-fat diet using female A/J mice. Groups 1 and 2 were fed a diet supplemented with MeIQx at a concentration of 600 ppm. Groups 1 and 3 received a diet containing 20% corn oil and group 4 was fed the basal diet alone. After 1 week, 10 mice in each group were sacrificed for measurement of cytochrome P450 (CYP)1A2 mRNA in the liver and lung. The remaining mice were maintained on their respective diets until termination, 32 weeks after the initial MeIQx treatment, when lung proliferative lesions were analyzed. The incidences and multiplicities of hyperplasias and adenomas in MeIQx-treated groups (groups 1 and 2) were significantly higher than in the groups without MeIQx treatment, with a significant increase in the incidences and multiplicities of adenomas + carcinomas, as well as hyperplasia + adenomas + carcinomas (lung proliferative lesions). Lung carcinomas were observed in 1 mouse in each of the MeIQx-treated groups. However, the high-fat diet (groups 1 and 3) did not affect the incidences or multiplicities of lung proliferative lesions. Expression levels of CYP1A2 mRNA after MeIQx treatment significantly increased >3-fold in livers, but no significant change was noted in the lungs, where levels were very low at 1/210 and 1/923 the values for livers. In conclusion, following a 32-week period, we confirmed the lung tumorigenic potential of MeIQx which possibly occurs due to proximate carcinogens activated by CYP1A2 in the liver. However, we failed to detect any influence of a high-fat diet.

Effect of rice and salty rice diets on the structure of mouse stomach

The effect of rice and salty rice diets on stomach morphology was investigated in Swiss/ICR mice. Mice were fed rice, salty rice, or standard pellet diets for 3-12 months, starting when the mice were 4 weeks of age. Long-term maintenance on the rice or salty rice diet increased the dimension and wet weight of the forestomach and decreased the same parameters of the glandular stomach. Similar bidirectional changes of the forestomach (hypertrophy) and glandular stomach (atrophy) were produced by hydrocortisone treatment. Histological study showed that a reduction in the parietal cell population accounted for the regression of the glandular stomach in both cases. Evidence is presented to suggest that an excess of carbohydrate and sodium chloride combined with a deficiency of fat and protein produced steroidal disorders that in turn gave rise to hyperplasia of the forestomach and atrophy of the glandular stomach of the mice. Possible impact of the above findings on the genesis of human gastric cancer is discussed in relation to the metabolic competence of the host animals to synthesize vitamin C.

Cancer prevention research - then and now

Throughout history, humankind has won the battle against deadly diseases, including small pox and polio, by defeating them through prevention. Cancer prevention is a global priority, but studying history suggests that the journey towards achieving this goal is difficult and full of detours and roadblocks. Epidemiology and clinical evidence clearly indicate that specific genetic, environmental and behavioural factors are associated with an increased risk for cancer development. What can we learn from the past that is applicable to the reality of successful cancer prevention?

Multi-targeted therapy of cancer by omega-3 fatty acids

Omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFAs) are essential fatty acids necessary for human health. Currently, the Western diet contains a disproportionally high amount of n-6 PUFAs and low amount of n-3 PUFAs, and the resulting high n-6/n-3 ratio is thought to contribute to cardiovascular disease, inflammation, and cancer. Studies in human populations have linked high consumption of fish or fish oil to reduced risk of colon, prostate, and breast cancer, although other studies failed to find a significant association. Nonetheless, the available epidemiological evidence, combined with the demonstrated effects of n-3 PUFAs on cancer in animal and cell culture models, has motivated the development of clinical interventions using n-3 PUFAs in the prevention and treatment of cancer, as well as for nutritional support of cancer patients to reduce weight loss and modulate the immune system. In this review, we discuss the rationale for using long-chain n-3 PUFAs in cancer prevention and treatment and the challenges that such approaches pose in the design of clinical trials.

Dietary fat-gene interactions in cancer

Epidemiologic studies have suggested for decades an association between dietary fat and cancer risk. A large body of work performed in tissue culture and xenograft models of cancer supports an important role of various types of fat in modulating the cancer phenotype. Yet, the molecular mechanisms underlining the effects of fat on cancer initiation and progression are largely unknown. The relationships between saturated fat, polyunsaturated fat, cholesterol or phytanic acid with cancer have been reviewed respectively. However, few have considered the relationship between all of these fats and cancer. The purpose of this review is to present a more cohesive view of dietary fat-gene interactions, and outline a working hypothesis of the intricate connection between fat, genes and cancer.

Seaweed and soy: companion foods in Asian cuisine and their effects on thyroid function in American women

Seaweeds and soy are two commonly eaten foods in Asia. Both have been reported to affect thyroid function, seaweed because of its iodine content and soy because of its goitrogenic effect. Twenty-five healthy postmenopausal women (mean age 58 years) completed a double-blinded randomized crossover study. Ten capsules (5 g/day) of placebo or seaweed (Alaria esculenta), providing 475 microg of iodine/day, were consumed daily for 7 weeks. A powdered soy protein isolate (Solae Co., St. Louis, MO), providing 2 mg of isoflavones/kg of body weight, was given daily during the last week of each treatment arm. On average, this provided 141.3 mg of isoflavones/day and 67.5 g of protein/day. Blood samples and 48-hour urine samples were collected before and after each intervention period, and urinary I/C (microg of iodine/g of creatinine) and serum thyroxine, free thyroxine index, total triiodothyronine, and thyroid stimulating hormone (TSH) were measured. Seaweed ingestion increased I/C concentrations (P < .0001) and serum TSH (P < .0001) (1.69 +/- 0.22 vs. 2.19 +/- 0.22 microU/mL, mean +/- SE). Soy supplementation did not affect thyroid end points. Seven weeks of 5 g/day seaweed supplementation was associated with a small but statistically significant increase in TSH. Soy protein isolate supplementation was not associated with changes in serum thyroid hormone concentrations.

Contributions of Ernst L. Wynder to chronic disease control worldwide and to preventive medicine

Ernst L. Wynder is internationally known for his important discoveries in the field of human chronic disease causation, that is the underlying mechanisms, studied in various animal models, as a foundation for recommendations on the prevention of these diseases. These include coronary heart disease, and the main human cancers including cancer of the lung, caused by traditional smoking habits, and the nutritionally linked cancers, namely cancer of the breast, prostate, colon, pancreas, and urinary bladder. Much of this research was performed in a chronic disease prevention institution--created by Dr. Wynder--the American Health Foundation. There were outreach programs to educate people about proper lifestyles to secure disease prevention, including beginning health education in children.

Differential effects of delivery of omega-3 fatty acids to human cancer cells by low-density lipoproteins versus albumin

PURPOSE

Omega-3 (n-3) fatty acids (FA) have been proposed to confer tumor-inhibitory properties. In vivo, dietary FA are delivered to tumor cells by two main routes: low-density lipoproteins (LDL) and albumin complexes. High FA concentration in LDL and up-regulation of LDL receptors in tumor cells suggest that the LDL receptor pathway may be the major route for FA delivery. We compared effects of n-3FA delivered to human cancer cells by LDL and albumin.

EXPERIMENTAL DESIGN

LDL was isolated from plasma of African Green monkeys fed diets enriched in fish oil (n-3 FA) or linoleic acid (n-6FA) and used to deliver FA to MCF-7 and PC3 cancer cells. Cell proliferation, apoptosis, and changes in global gene expression were monitored.

RESULTS

Both LDL and albumin were effective in delivering FA to tumor cells and modifying the composition of cell phospholipids. The molar ratio of 20:4 (n-6) to 20:5 (n-3) in phosphatidylcholine and phosphatidylethanolamine was profoundly decreased. Although cell phospholipids were similarly modified by LDL and albumin-delivered FA, effects on cell proliferation and on transcription were markedly different. LDL-delivered n-3 FA were more effective at inhibiting cell proliferation and inducing apoptosis. Expression microarray profiling showed that a significantly higher number of genes were regulated by LDL-delivered than albumin-delivered n-3 FA with little overlap between the two sets of genes.

CONCLUSIONS

These results show the importance of the LDL receptor pathway in activating molecular mechanisms responsible for the tumor inhibitory properties of n-3FA.

From carcinogenesis to clinical interventions for cancer prevention

During the last three decades, the scientific community has made immense progress in acquiring the knowledge needed to prevent cancer. Pioneering research helped to identify potential causes of cancer, particularly environmental factors such as diet, and provided insight regarding their mechanisms-of-action. Concurrently, promising inhibitors of cancer that appeared able to either arrest or reverse cancer development by interfering with one or more steps in the process of carcinogenesis were identified and systematically evaluated for their potential as chemopreventive agents. Numerous agents determined to be safe and effective in preclinical trials have been and continue to be tested in Phase I,II, and III clinical interventions for cancers at various sites, including breast, colon, prostate, esophagus, mouth, lung, cervix, endometrium, ovary, liver, bladder, and skin. The development of valid intermediate biomarkers that can serve as surrogate endpoints for clinical disease is urgently needed to accelerate advances in clinical trials for cancer prevention.

Effects of dietary fat on benz-a-pyrene-induced forestomach tumorigenesis in mice chronically exposed to arsenic

The modulating effect of As (As2O3) in drinking water plus dietary fatty acids on benzo-a-pyrene (BP) induced forestomach tumorigenesis was assayed in mice fed with corn oil (CO), Olein (O), palmstearin (PS) and cod liver oil (CLO) enriched formulae, and a mixed-fat (S-stock) diet during 28 weeks. Neither pre-or neoplastic lesions were recorded in esophagus or forestomach of mice treated with As alone. CLO diet showed a protective effect. Indeed, multiple epidermal hyperplasia were significantly reduced compared to S group and a reduction in papillomas multiplicity with respect to S, CO and O groups was also observed. Mice fed on PS formula showed minor papillomas per mouse with respect to CO and O. These results indicate that As plus BP did not exhibit any synergistic effect on the development of epidermoid tumor lesions, whereas CLO diet exerted antipromoting activity . In spite of their common essential fatty acid deficiency (EFAD) condition, PS and O lots showed contradictory results. Hence, the dietary enrichment in 18:1 n-9 (O diet) per se, and not the EFAD state, may play a deleterious role. Corn diet showed no promoting activity on the epidermoid tumor development in this model.

Vegan proteins may reduce risk of cancer, obesity, and cardiovascular disease by promoting increased glucagon activity

Amino acids modulate the secretion of both insulin and glucagon; the composition of dietary protein therefore has the potential to influence the balance of glucagon and insulin activity. Soy protein, as well as many other vegan proteins, are higher in non-essential amino acids than most animal-derived food proteins, and as a result should preferentially favor glucagon production. Acting on hepatocytes, glucagon promotes (and insulin inhibits) cAMP-dependent mechanisms that down-regulate lipogenic enzymes and cholesterol synthesis, while up-regulating hepatic LDL receptors and production of the IGF-I antagonist IGFBP-1. The insulin-sensitizing properties of many vegan diets--high in fiber, low in saturated fat--should amplify these effects by down-regulating insulin secretion. Additionally, the relatively low essential amino acid content of some vegan diets may decrease hepatic IGF-I synthesis. Thus, diets featuring vegan proteins can be expected to lower elevated serum lipid levels, promote weight loss, and decrease circulating IGF-I activity. The latter effect should impede cancer induction (as is seen in animal studies with soy protein), lessen neutrophil-mediated inflammatory damage, and slow growth and maturation in children. In fact, vegans tend to have low serum lipids, lean physiques, shorter stature, later puberty, and decreased risk for certain prominent 'Western' cancers; a vegan diet has documented clinical efficacy in rheumatoid arthritis. Low-fat vegan diets may be especially protective in regard to cancers linked to insulin resistance--namely, breast and colon cancer--as well as prostate cancer; conversely, the high IGF-I activity associated with heavy ingestion of animal products may be largely responsible for the epidemic of 'Western' cancers in wealthy societies. Increased phytochemical intake is also likely to contribute to the reduction of cancer risk in vegans. Regression of coronary stenoses has been documented during low-fat vegan diets coupled with exercise training; such regimens also tend to markedly improve diabetic control and lower elevated blood pressure. Risk of many other degenerative disorders may be decreased in vegans, although reduced growth factor activity may be responsible for an increased risk of hemorrhagic stroke. By altering the glucagon/insulin balance, it is conceivable that supplemental intakes of key non-essential amino acids could enable omnivores to enjoy some of the health advantages of a vegan diet. An unnecessarily high intake of essential amino acids--either in the absolute sense or relative to total dietary protein--may prove to be as grave a risk factor for 'Western' degenerative diseases as is excessive fat intake.

Modulating effects of diets high in omega-3 and omega-6 fatty acids in initiation and postinitiation stages of diethylnitrosamine-induced hepatocarcinogenesis in rats

The effects of sardine fish oil or corn oil on diethylnitrosamine (DEN)-induced hepatocarcinogenesis were investigated in male F344 rats. Starting at 5 weeks of age, animals were divided into 11 groups and fed 23.5% corn oil (HCO) (groups 1 and 7) or 5% corn oil (LCO) (groups 2 and 8), 22.5% sardine oil + 1% corn oil (FO) semipurified diet (groups 3 and 9) or basal diet (CE-2) (groups 4-6, 10 and 11). At 6 weeks of age, all animals except the vehicle-treated groups were given DEN (200 mg/kg body weight, i.p. once weekly for 3 weeks). One week after the final exposure to DEN, groups 1-3 were changed to the basal diet, and groups 4-6 were switched to the HCO, LCO or FO diet, respectively. Animals in groups 1-3 and 10 were given drinking water containing 0.05% phenobarbital (PB). Liver sections from the animals at the termination of the experiment (24 weeks) were doubly stained for glutathione S-transferase placental form (GST-P) and silver-stained nucleolar organizer regions (AgNORs). The multiplicity of hepatocellular neoplasms of group 1 was significantly larger than that of group 2 or 3. The number of GST-P-positive foci of group 2 or 3 was significantly smaller than that of group 1. Among the groups fed the experimental diets in the postinitiation phase (groups 4-6), no significant difference was found in the incidence of liver tumors. AgNORs values of the enzyme-altered foci in rats of the HCO diet groups were larger than those of the other diet groups. These results indicate that the enhancing effect of a high dose of corn oil in hepatocarcinogenesis is mainly present during the initiation phase but not during postinitiation phase, and fish oil rich in polyunsaturated omega-3 fatty acids could inhibit DEN-induced hepatocarcinogenesis in rats.

Effect of evening primrose and fish oils on two stage skin carcinogenesis in mice

The effect of fish oil (FO, given in the form of MaxEPA) rich in n-3 fatty acids and evening primrose oil (EPO) rich in n-6 fatty acids on two-stage skin carcinogenesis in mice was studied. Both FO and EPO inhibited the papilloma formation to a significant degree only during the promotion stage which was associated with an increase in lipid peroxidation. Both FO and EPO inhibited the binding of benzo(a)-pyrene to skin cell DNA suggesting that this could be one of the mechanism(s) by which these oils could be preventing papilloma development. Neither EPO nor FO influenced epidermal cell proliferation. In the FO group, LA (linoleic acid), AA (arachidonic acid) and DHA (docosahexaenoic acid) were increased, whereas in the EPO group a significant increase in the AA content was noted. No specific changes in the fatty acid pattern were observed in any of the groups that could be attributed to the papilloma incidence. These results suggest that FO and EPO can influence papilloma formation which can be attributed, at least in part, to their ability to prevent benzo(a)pyrene binding to DNA and to an increase the lipid peroxidation process.

Effect of cis-unsaturated fatty acids on Meth-A ascitic tumour cells in vitro and in vivo

Earlier studies performed both by us and by others have demonstrated that some n-3 and n-6 fatty acids can inhibit the growth of tumour cells in vitro. Though studies done with various types of oils rich in n-3 and n-6 fatty acids did show that the tumour incidence and growth can be modified, there were relatively few studies wherein the anti-tumour effects of individual free fatty acids were studied. Here we present results which suggest that free fatty acids (oleic acid (OA), linoleic acid (LA), alpha-linolenic acid (ALA), gamma-linolenic acid (GLA), arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) can inhibit the growth of methylcholanthrene-induced sarcoma cells (Meth-A cells) in vitro. The order of potency of various fatty acids on the growth of Meth-A cells was DHA > ALA > EPA > AA > GLA > LA > OA and their ID50 values were 10, 20, 35, 45, 68, 73 and 110 microg/ml/1 x 10(4) cells, respectively. These results indicate that the inhibitory action of different types of n-3, n-6 and n-9 fatty acids on Meth-A cells does not depend on their unsaturation. Vitamin E could partially block the cytotoxicity of these fatty acids indicating a possible role for free radicals. GLA, AA and EPA augmented the generation of superoxide anion and lipid peroxidation in Meth-A cells indicating a possible correlation between the ability of fatty acids to augment free radicals and their tumoricidal action. In an in vivo study, it was observed that OA, LA, ALA, GLA and EPA can prolong the survival of Meth-A-bearing mice when given intraperitoneally. Of all the fatty acids tested, surprisingly, LA was found to be the most potent in enhancing the survival of the tumour-bearing animals at all the concentrations tested. Thus, these studies suggest that free fatty acids can inhibit Meth-A tumour cell proliferation both in vitro and in vivo.

Dietary fiber, Hispanics, and breast cancer risk?

The cancer rates of immigrant populations in the United States must be taken into account when looking at the importance of diet and culture as it relates to cancer prevention. Unfortunately, some nutrition studies targeted toward nontraditional white populations have not adequately confronted the issue of cultural meaning in efforts to gather dietary data accurate enough to support nutritional analyses, identify marginal diets, or relate risk to dietary patterns. The study presented here resolves many of the culturally specific issues utilizing awareness, attention, and judicious combination of culturally sensitive qualitative and quantitative research techniques. The importance of such a study in an Hispanic population is based on the fact that the age-adjusted rate of breast cancer in countries such as Mexico is among the lowest in the world. In addition, although one of the fastest-growing minority groups in the United States, Hispanic women living in this country have been shown to have the lowest incidence of the mortality rates from this disease across most geographic regions of the United States. Therefore, one might speculate that dietary factors, which have been shown to play a role in breast cancer prevention, may account for this difference. It is well recognized that the traditional Hispanic diet is rich in protective nutrients such as dietary fiber. It is known that through complex mechanisms, dietary fiber works to reduce the amount of estrogens in the body. Research also indicates that it is the level of endogenous estrogen in the body that may influence the onset of breast cancer. In order to better understand how dietary factors may be associated with breast cancer in Hispanic women, it is important that one develop the proper tools to discern any potential differences. Therefore, we developed an approach to obtaining dietary fiber information from a small cohort of 22 Houston-area Hispanic women as a vanguard study for a larger breast cancer prevention trial. Two separate dietary assessment instruments were utilized, a three-day food record and the Southwest Food Frequency Questionnaire. The mean intake of dietary fiber was 16 g/day according to the food record and 21 g/day according to the SWFFQ. Fruits, vegetables, breads, cereals, and beans provided for most of the participants' dietary fiber intake. These results support evidence that the Hispanic population's dietary fiber intake is higher than that for other groups, and this may help explain the lower incidence of breast cancer among some Hispanic populations.

Fat, fish, fish oil and cancer

There is an ecological association between total and animal fat consumption and colorectal and breast cancer risk. Mortality data for breast and colorectal cancer for 24 European countries correlated, as expected, with the consumption of animal, but not vegetable, fat. There was an inverse correlation with fish and fish oil consumption, when expressed as a proportion of total or animal fat, and this correlation was significant for both male and female colorectal cancer and for female breast cancer, whether the intakes were in the current time period, or 10 years or 23 years before cancer mortality. These effects were only seen in countries with a high ( > 85 g caput-1 day-1) animal fat intake. This evidence suggests that fish oil consumption is associated with protection against the promotional effects of animal fat in colorectal and breast carcinogenesis.

Effect of dietary fat on diethylnitrosamine induced hepatocarcinogenesis in Wistar rats

In a diethylnitrosamine (DEN) induced hepatoma model, the effect of fish oil, a rich source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and ground nut oil, a rich source of oleic acid (OA) and linoleic acid (LA), was studied. Both 20% fish oil and ground nut oil inhibited DEN-induced hepatocarcinogenesis in rats. Contrary to general belief, an inverse correlation was observed between the development of neoplastic nodules and the amount of lipid peroxides formed in the high fat (20% fish oil and ground nut oil) diet groups, indicating that the higher the lipid peroxides formed, the lower the incidence of liver tumours in DEN-treated animals. Results of the analysis of liver fatty acid composition of the phospholipid fraction suggested that DEN and fish oil treatment can inhibit the activity of the delta-6 and 5-desaturases. It is concluded from the results of the present study that a 'high fat' diet and lipid peroxidation can modulate DEN-induced hepatocarcinogenesis in rats.

Flavonoid inhibition of aromatase enzyme activity in human preadipocytes

Eleven flavonoid compounds were compared with aminoglutethimide (AG), a pharmaceutical aromatase inhibitor, for their abilities to inhibit aromatase enzyme activity in a human preadipocyte cell culture system. Flavonoids exerting no effect on aromatase activity were catechin, daidzein, equol, genistein, beta-naphthoflavone (BNF), quercetin and rutin. The synthetic flavonoid, alpha-naphthoflavone (ANF), was the most potent aromatase inhibitor, with an I50 value of 0.5 microM. Three naturally-occurring flavonoids, chrysin, flavone, and genistein 4'-methyl ether (Biochanin A) showed I50 values of 4.6, 68, and 113 microM, respectively, while AG showed an I50 value of 7.4 microM. Kinetic analyses showed that both AG and the flavonoids acted as competitive inhibitors of aromatase. The Ki values, indicating the effectiveness of inhibition, were 0.2, 2.4, 2.4, 22, and 49 microM, for ANF, AG, chrysin, flavone, and Biochanin A, respectively. Chrysin, the most potent of the naturally-occurring flavonoids, was similar in potency and effectiveness to AG, a pharmaceutical aromatase inhibitor used clinically in cases of estrogen-dependent carcinoma. These data suggest that flavonoid inhibition of peripheral aromatase activity may contribute to the observed cancer-preventive hormonal effects of plant-based diets.

Hypothesis: dietary management may improve survival from nutritionally linked cancers based on analysis of representative cases

A limited number of case histories was analyzed and verified to examine the effect of a very low fat, moderately high fiber, and moderately reduced calorie diet on the survival and quality of life of patients with primary cancer of the pancreas, metastatic stage D2 prostate cancer, and other nutritionally linked cancers. The retrospective study of pancreatic cancer patients disclosed that 1-year survival was higher among those who modified their diets than in those for whom there was no evidence as to diet alteration. For patients with metastatic prostate cancer (stage D2), a case control study demonstrated a statistical association of dietary modification with longer survival and improved quality of life. A retrospective study utilizing questionnaires supported such dietary modifications as a useful tool in the management of nutritionally linked cancers.

The effect of the fiber components cellulose and lignin on experimental colon neoplasia

Sixty Sprague-Dawley rats were pair-fed one of three nutritionally identical diets. One diet contained "low-fiber" (3.8% crude fiber); the others contained "high fiber" (28.7% crude fiber) composed of either cellulose or lignin. Although both "high fiber" diets had similar stool bulking effects, only the cellulose diet was associated with a reduction in 1,2-dimethylhydrazine (DMH)-induced colon neoplasms. The cellulose diet was also associated with distinct changes in the gut bacterial profile and with a lowered serum cholesterol.

Dose-dependent effects of dietary phytosterol on epithelial cell proliferation of the murine colon

Phytosterols are a group of compounds in plants that have been found to inhibit tumour development and decrease enhanced colonic epithelial cell proliferation in carcinogen-treated rats. The mechanism by which phytosterols may inhibit tumour development and alter cell proliferation is unknown. However, studies have shown that dietary phytosterol intake may alter levels of certain promoters in the colonic lumen, leading to altered levels of colonic epithelial cell proliferation. In this study, the effect of dietary phytosterol on the proliferative status of the intestinal epithelium was investigated in mice. Inbred C57B1/6J mice were fed semi-synthetic diet (control); 0.1% cholic acid, 0% phytosterol (cholic acid control); and cholic acid plus 0.3, 1.0 or 2.0% phytosterol. Dietary cholic acid significantly increased colonic epithelial cell proliferation and the highest labelled cell position by 92 and 35%, respectively. Phytosterol significantly reduced the enhanced labelling index and the position of the highest labelled cell in a dose-dependent manner. Mitotic index was also reduced significantly by phytosterol but not in a dose-dependent manner. The results of this study indicate that phytosterol influences the colonic epithelial cell morphometrics, that are important preneoplastic events in colon carcinogenesis, and may thus contribute to a reduced risk of cancer.

Milk cream does not enhance 2,7-dimethylbenz[a]anthracene-induced mammary tumorigenesis

We have previously reported that a diet enriched with butter showed an inhibitory effect on the development of mammary tumors in mice and rats. To solve the problem of whether the inhibitory effect of butter was caused by lipids of cow's milk, we have studied the effects of dried milk (WM), skim milk (SM) and milk cream (CR) on mammary tumorigenesis in rats. The lowest incidence of mammary tumors was observed in the CR group, although the difference from other groups was statistically not significant. However, the number of papillary carcinomas in the CR group was significantly lower than the WM group. The result indicates that milk lipids have no enhancing effect on mammary tumorigenesis.

The role of dietary phytosterols in colon carcinogenesis

Epidemiological and experimental studies have shown that increased intake of plant foods and decreased meat consumption are correlated with a decreased risk for colon cancer. Many components of plant foods are suggested to mitigate colon carcinogenesis, including vitamins, minerals, and dietary fiber. Phytosterols are a common component of plant foods consumed in relatively large quantities by vegetarians, who are at lower risk for colon cancer development than individuals on a Western diet low in phytosterols. In addition, phytosterols have been shown experimentally to inhibit colon cancer development. Dietary cholesterol, although structurally similar to the phytosterols, is correlated etiologically to the incidence of colon cancer, with changes in serum cholesterol levels and fecal bile acid profiles suggested to increase susceptibility to colon tumorigenesis. The objective of this paper is to discuss the effect of dietary phytosterols on cholesterol and bile acid metabolism and how these effects may lead to a decreased risk for colon cancer development.

Effects of a long-chain fatty amine on mammary carcinogenesis induced in female Sprague-Dawley rats by DMBA

Reports that protein kinase C is inhibited by sphingosine and other long-chain amines and the suggestion that promotion of mammary carcinogenesis by dietary fat is mediated by protein kinase C prompted us to investigate the effects of a long-chain amine, 1-octadecylamine, on mammary carcinogenesis induced by 7,12-dimethylbenz[a]anthracene in rats fed a high-fat diet. Rats fed the amine sulfate at a level of 0.01% in a semipurified diet containing 20% corn oil developed more tumors than those fed the high-fat diet alone, although body weight gain was inhibited slightly. Rats fed the amine sulfate at 0.1% of the diet developed very few tumors compared with those fed either the high-fat diet or a low-fat diet containing 5% corn oil. At the higher level, the C18 amine also caused a marked inhibition of body weight gain.

The effect of flaxseed supplementation on early risk markers for mammary carcinogenesis

Since lignans have been suggested to have some cancer-protective effects, flaxseed, the most abundant source of lignan precursors, was tested for its effect on early markers of risk for mammary carcinogenesis. Supplementation of a high-fat diet with flaxseed flour (FF) or defatted flaxseed meal (FM) (5% or 10%) reduced the epithelial cell proliferation by 38.8-55.4% and nuclear aberrations by 58.8-65.9% in female rat mammary gland, with optimum effects seen with the 5% FF. These protective effects were accompanied by increases in urinary lignan excretion indicating that they may be related to the ability of flaxseed to provide lignan precursors.

The relationship between animal fat intake, cigarette smoking, and lung cancer

An international ecologic study on the relationship between fat intake, cigarette consumption, and age-specific lung cancer mortality rates was conducted using data obtained from 29 countries. The 1969-71 and 1984-86 mortality rates for lung cancer were related to smoking habits and to levels of animal fat intake. Highly significant independent positive correlations for lung cancer with both cigarette smoking and animal fat consumption were seen. No significant independent relationship was found between lung cancer mortality and vegetable fat consumption. In a multiple regression analysis linking lung cancer mortality to dietary intake of animal fat, cigarette smoking, and the interaction term between cigarette smoking and animal fat intake, only the latter term was significant (P less than 0.001) pointing towards a role for animal fat as a promoter of lung cancer.

Dietary modulation of experimental neoplastic development: role of fat and fiber content and calorie intake

Cancer is still one of the major causes of death in the industrialized countries but locally prevailing lifestyles may dictate the kinds of cancer seen among populations of different geographical areas. Dietary habits and, in particular, the nature and/or the amount of fat, calorie and/or vegetable fiber which are consumed in these countries are among the most frequently quoted etiological factors which may account for this situation. Epidemiological and experimental evidence has accumulated which, even though it can be used to support these conclusions, is still a matter of considerable debate. Modulation of neoplastic development is a concept which has been elaborated to overcome the fact that many experimental observations are not really taken into consideration by the classical 2-step theory of carcinogenesis. It is defined as the effect of any treatment which given before, during or after the initiation of a full carcinogenic process modifies the pattern of neoplastic development as evaluated by the kinetics of appearance, the incidence and/or the yield of histologically characterized malignant tumors. It is said to be positive or negative depending on whether it accelerates or slows down the process and increases or decreases the yield of malignant tumors respectively. From a review of the available experimental data, it is concluded that fat per se has, most probably, no modulating effect but that unbalanced diets rich in lipids could act as a positive modulator of chemically induced carcinogenesis by virtue of their capacity to cause a break in metabolic and proliferative homeostasis; that vegetable fibers as well as restriction in calorie intake could act as negative modulators of the same process because they could restore or help restore this homeostasis. It is thus proposed that to maintain dietary balance either by increasing fiber and/or by reducing total calorie intake is the most effective way to negatively modulate chemically induced carcinogenesis in experimental animals. To make the same recommendation to humans could most probably help preventing major cancers like breast and colon cancers.

Mammalian lignan production from various foods

Mammalian lignans such as enterolactone and enterodiol, which are produced in the colon from precursors in foods, have been suggested as playing a role in the cancer-protective effect of vegetarian diets. Despite this, very little is known regarding the amount that is produced from different food products. Therefore, the objective of this study was to determine the production of mammalian lignans from 68 common plant foods by using the technique of in vitro fermentation with human fecal microbiota, which simulates colonic fermentation. Results showed a wide range (21-67,541 microgram(s)/100 g sample) in the amount of lignans produced. On the average as a group, the oilseeds produced the highest amounts (20,461 +/- 12,685), followed by the dried seaweeds (900 +/- 247), whole legumes (562 +/- 211), cereal brans (486 +/- 90), legume hulls (371 +/- 52), whole grain cereals (359 +/- 81), vegetables (144 +/- 23), and fruits (84 +/- 22). The vegetables produced the second highest concentration of lignans (1,546 +/- 280) when the data were expressed on a moisture-free basis. Flaxseed flour and its defatted meal were the highest producers of lignans (mean 60,110 +/- 7,431). Lignan production with the in vitro method related well to the urinary lignan excretion observed in rats and humans. The data should be useful in the estimation of lignan production from a given diet and in the formulation of high-lignan-producing diet for the purpose of reducing the cancer risk.

Effect of dietary kelp on lipid peroxidation and glutathione peroxidase activity in livers of rats given breast carcinogen DMBA

In our previous study of female rats, a diet containing 2% of powdered fronds of Laminaria religiosa (kelp) had a remarkable inhibitory effect on mammary tumorigenesis induced by orally given 7,12-dimethylbenz[a]anthracene (DMBA). In this study, the effect of the dietary kelp on lipid peroxidation and glutathione peroxidase (GSH-Px) activity in the liver was studied in the same experimental system. Two separate short- and long-term experiments were carried out on rats fed a diet with 2% kelp. DMBA (20 mg/kg body wt) was given to each animal 7 days after feeding began in short-term experiment and 27 days later in long-term experiment. Livers of all rats were obtained for quantitative determination and for histopathologic observation. Lipoperoxide in livers of the kelp-fed rats was of normal value, almost the same as that of untreated control rats; however, lipoperoxide in livers of control rats was significantly higher than in the other two groups in both experiments. A marked fatty change in livers of control rats was demonstrated in hepatic cells in peripheral zones of lobules in long-term experiment but not in short-term experiment. In long-term experiment, the amounts of GSH-Px and selenium in livers of kelp-fed rats were slightly less than those in untreated control rats but more than those in control rats. There was a more-intense positive reaction in the hepatic cells in the peripheral zones of the lobules in the kelp-fed and untreated rats and a less-intense positive reaction in control rats.(ABSTRACT TRUNCATED AT 250 WORDS)