Total N-nitroso compounds and their precursors in hot dogs and in the gastrointestinal tract and feces of rats and mice: possible etiologic agents for colon cancer

Microbial nitroreductases: A versatile tool for biomedical and environmental applications

Nitroreductases, enzymes found mostly in bacteria and also in few eukaryotes, use nicotinamide adenine dinucleotide (NADH) or nicotinamide adenine dinucleotide phosphate (NADPH) as a cofactor for their activity and metabolize an enormous list of a diverse nitro group-containing compounds. Nitroreductases that are capable of metabolizing nitroaromatic and nitro heterocyclic compounds have drawn great attention in recent years owing to their biotechnological, biomedical, environmental, and human impact. These enzymes attracted medicinal chemists and pharmacologists because of their prodrug selectivity for activation/reduction of nitro compounds that wipe out pathogens/cancer cells, leaving the host/normal cells unharmed. It is applied in diverse fields of study like prodrug activation in treating cancer and leishmaniasis, designing fluorescent probes for hypoxia detection, cell imaging, ablation of specific cell types, biodegradation of nitro-pollutants, and interpretation of mutagenicity of nitro compounds. Keeping in view the immense prospects of these enzymes and a large number of research contributions in this area, the present review encompasses the enzymatic reaction mechanism, their role in antibiotic resistance, hypoxia sensing, cell imaging, cancer therapy, reduction of recalcitrant nitro chemicals, enzyme variants, and their specificity to substrates, reaction products, and their applications.

Maternal diet before and during pregnancy and risk of asthma and allergic rhinitis in children

BACKGROUND

Consumption of certain foods during pregnancy has been shown to have beneficial effects on childhood asthma and allergic disease development and aggravation. However, most studies provide conflicting results and the relationships between maternal preconceptional diet and risks of childhood asthma and allergic disease have not previously been explored. The objective of this study was to assess maternal diet during the year before pregnancy and the last 3 months of pregnancy and investigate their associations with the risks of asthma, wheezing, allergic rhinitis and atopic dermatitis in young children.

METHODS

The study sample consisted of 1140 mother-child pairs from the EDEN cohort. Mothers had responded to the food frequency questionnaires used to assess diet before and during pregnancy. Children were followed up using health questionnaires. The health outcomes studied were: asthma, wheezing, allergic rhinitis and atopic dermatitis by the age of 3 years.

RESULTS

Using multivariable-adjusted logistic regression models, significant inverse associations were observed between cooked green vegetable consumption before pregnancy and childhood asthma; consumption of eggs and raw vegetables before and during pregnancy, consumption of grains before pregnancy, and consumption of cooked green vegetables during pregnancy and allergic rhinitis. For the first time, a significant positive association was found between meat intake during the preconceptional period and a risk of wheezing, allergic rhinitis and atopic dermatitis.

CONCLUSIONS

Based on our findings, preconceptional and prenatal maternal intake of certain type of food groups may be preventive against asthma, wheezing and allergic rhinitis, whereas higher maternal intake of meat before pregnancy may increase the risk of wheezing, allergic rhinitis and atopic dermatitis in young children.

Dietary intake of polyphenols and risk of colorectal cancer and adenoma-A case-control study from Iran

OBJECTIVES

The aim of this study is to examine the relationship between dietary polyphenols' classes and individual polyphenol subclasses and also the risk of Colorectal cancer (CRC) and colorectal adenomas (CRA).

DESIGN

A hospital-based case-control study on the association between CRC and CRA and dietary polyphenols was conducted.

SETTING

Overall, 129 colorectal cancers, 130 colorectal adenoma cases and 240 healthy controls were studied in three major general hospitals in Tehran province, Iran.

RESULTS

In a multivariate-adjusted model for potential confounders, higher consumption of stilbenes (OR 0.49 for the highest vs. the lowest quartile; 95% CI = 0.24-0.99; p for trend = 0.013) was associated with the decreased risk of CRA. Moreover, an inverse association between the risk of CRC and the intake of total polyphenols (OR 0.05 for the highest vs. the lowest quartile; 95% CI = 0.01-0.19; p for trend=<0.001), total flavonoids (OR 0.36 for the highest vs. the lowest quartile; 95% CI = 0.16-0.79; p for trend = 0.005), total phenolic acids (OR 0.24 for the highest vs. the lowest quartile; 95% CI = 0.10-0.56; p for trend = 0.002), anthocyanin (OR 0.21 for the highest vs. the lowest quartile; 95% CI = 0.08-0.55; p for trend = 0.001) and flavanols (OR 0.38 for the highest vs. the lowest quartile; 95% CI = 0.17-0.85; p for trend = 0.001) was observed.

CONCLUSION

The present study showed that a higher intake of total polyphenols, total flavonoids, total phenolic acids anthocyanin and flavanols was related to the decreased risk of CRC. The higher consumption of stilbenes was also inversely associated with the risk of CRA.

Dietary poultry intake and the risk of stroke: A dose-response meta-analysis of prospective cohort studies

BACKGROUND & AIMS

We performed a meta-analysis to illuminate and quantify the potential relationship between poultry intake and risk of stroke through summarizing available evidence using a dose-response meta-analysis of prospective cohort studies.

METHODS

Pertinent prospective cohort studies attained using electronic searches through PubMed, and Scopus up to September 25th, 2017. Relative risks (RR) s with corresponding 95% confidence intervals (CIs) of the highest versus the lowest for cohort studies were evaluated using DerSimonian and Laird random-effects models to find combined RRs. We also assessed the dose-response effect of this relationship.

RESULTS

A total of 7 studies involving 354 718 participants were met inclusion criteria. The pooled RR of total stroke risk was [RR = 0.92 95% CI, 0.82, 1.03, I² = 19.8%, P_{heterogeneity} = 0.28] for the highest versus lowest categories of poultry intake. Subgroup analysis showed an inverse associations for the US people [RR = 0.86 95% CI, 0.77, 0.95, I² = 0.0%, P_{heterogeneity} = 0.38] and women [RR = 0.83, 95% CI, 0.72, 0.93, I² = 0.0%, P_{heterogeneity} = 0.63]. We did not obtain any significant association in the subtypes of strokes with highest versus lowest poultry intake [Ischemic stroke (RR = 0.91; 95% CI: 0.79, 1.02, I² = 0.0%, p = 0.93), Hemorrhagic (RR = 0.82; 95% CI: 0.59, 1.04, I² = 20.5%, P_{heterogeneity} = 0.28)]. One serving per week increment in poultry intake was not associated with the risk of stroke (RR: 1.00, 95% CI: 0.96, 1.03, I² = 69.0%, P_{heterogeneity} = 0.004). Nonlinear dose-response meta-analysis showed lower risk of stroke at consumption ∼1 serving/week.

CONCLUSION

Our meta-analysis revealed that poultry intake is not associated with total stroke risk; furthermore, an inverse relationship in US population and females must be interpreted with caution.

Diet, microbiota, and dysbiosis: a 'recipe' for colorectal cancer

The food we consume feeds not only us, but also a vast and diverse community of microbiota within our gastrointestinal tract. In a process of symbiotic co-evolution, the gut microbiota became essential for the maintenance of the health and integrity of our colon. The advent of next-generation DNA sequencing technology and metabolic profiling have, in the recent years, revealed the remarkable complexity of microbial diversity and function, and that the microbiota produce a wide variety of bioactive products that are not only active at the mucosal surface, but also absorbed and circulated throughout the body, influencing distant organ health and function. As a result, several microbiota compositional patterns and their associations with both health and disease states have been identified. Importantly, a disturbed microbiota-host relationship, termed dysbiosis, is now recognized to be the root cause for a growing list of diseases, including colorectal cancer (CRC). There is mounting in vitro and in vivo evidence to suggest that diet selects for the microbiota composition and several health promoting and deleterious effects of diet are, in fact, mediated by the microbiota. Recent findings of the feasibility of dietary fiber to boost the colonic microbial synthesis of anti-proliferative and counter carcinogenic metabolites, particularly butyrate, underscores the prerequisite of dietary modification as a key measure to curb the pandemic of CRC in westernized countries. Better understanding of the diet-microbiota interplay and large-scale studies to evaluate the efficacy of dietary modification and gut microbiota modulation in reversing dysbiosis and restoring health could offer novel preventative and/or therapeutic strategies against westernized diseases, which are now considered the chief threat to public health.

Epidemiology and trend of common cancers in Iran (2004-2008)

BACKGROUND

Cancer is one of the most important causes of mortality worldwide. It includes approximately 13% of death cases. This study aimed to investigate the incidence trend of common cancers in Iran during 2004-2008 to improve reporting distribution the disease.

METHODS

This was a retrospective study. The study population was all cases of cancer diagnosed in Iran during 2004-2008. The crude incidence rate of cancers was calculated per 100 000 people by age groups and sex. Age-standardised incidence rates (ASRs) were calculated using direct standardisation and the world standard population. Data were analysed using SPSS (version 17) and Microsoft Office Excel 2007.

RESULTS

In this study, a total of 301 055 cases of cancer were diagnosed. ASRs were 60.51 and 84.51 in women and men respectively. Most common cancers in men were skin (ASR = 18.85), stomach (15.02), bladder (ASR = 11.25), prostate (ASR = 8.93) and colorectal (ASR = 8.29). Most common cancers in women were breast (ASR = 18.24), skin (ASR = 12.01), colorectal (ASR = 7.75), stomach (ASR = 7.05) and haematocyte (ASR = 4.01).

CONCLUSION

A significant increase was observed in the incidence of cancers in the country. Therefore, it is necessary to perform screening, early diagnosis and treatment in early stages of cancers.

Nitrate in drinking water and bladder cancer risk in Spain

BACKGROUND

Nitrate is a widespread contaminant in drinking water and ingested nitrate under conditions resulting in endogenous nitrosation is suspected to be carcinogenic. However, the suggested association between nitrate in drinking water and bladder cancer remains inconsistent. We evaluated the long-term exposure to drinking water nitrate as a risk factor for bladder cancer, considering endogenous nitrosation modifiers and other covariables.

METHODS

We conducted a hospital-based case-control study of bladder cancer in Spain (1998-2001). Residential histories and water consumption information were ascertained through personal interviews. Historical nitrate levels (1940-2000) were estimated in study municipalities based on monitoring records and water source. Residential histories of study subjects were linked with nitrate estimates by year and municipality to calculate individual exposure from age 18 to recruitment. We calculated odds ratios (OR) and 95% confidence intervals (CI) for bladder cancer among 531 cases and 556 controls with reliable interviews and nitrate exposure information covering at least 70% of years from age 18 to interview.

RESULTS

Average residential levels ranged from 2.1mg/L to 12.0mg/L among regions. Adjusted OR (95%CI) for average residential levels relative to ≤ 5 mg/L were 1.2 (0.7-2.0) for >5-10mg/L and 1.1 (0.6-1.9) for >10mg/L. The OR for subjects with longest exposure duration (>20 years) to highest levels (>9.5mg/L) was 1.4 (0.9-2.3). Stratification by intake of vitamin C, vitamin E, meat, and gastric ulcer diagnosis did not modify these results. A non-significant negative association was found with waterborne ingested nitrate with an OR of 0.7 (0.4-1.0) for >8 vs. ≤ 4 mg/day. Adjustment for several covariables showed similar results to crude analyses.

CONCLUSION

Bladder cancer risk was inconsistently associated with chronic exposure to drinking water nitrate at levels below the current regulatory limit. Elevated risk is suggested only among subjects with longest exposure duration to the highest levels. No evidence of interaction with endogenous nitrosation modifiers was observed.

Fat content and nitrite-curing influence the formation of oxidation products and NOC-specific DNA adducts during in vitro digestion of meat

The effects of fat content and nitrite-curing of pork were investigated on the formation of cytotoxic and genotoxic lipid oxidation products (malondialdehyde, 4-hydroxy-2-nonenal, volatile simple aldehydes), protein oxidation products (protein carbonyl compounds) and NOC-specific DNA adducts (O⁶-carboxy-methylguanine) during invitro digestion. The formation of these products during digestion is suggested to be responsible for the association between red meat and processed meat consumption and colorectal cancer risk. Digestion of uncured pork to which fat was added (total fat content 5 or 20%), resulted in significantly higher lipid and protein oxidation in the mimicked duodenal and colonic fluids, compared to digestion of pork without added fat (1% fat). A higher fat content also significantly favored the formation of O⁶-carboxy-methylguanine in the colon. Nitrite-curing of meat resulted in significantly lower lipid and protein oxidation before and after digestion, while an inconsistent effect on the formation of O⁶-carboxy-methylguanine was observed. The presented results demonstrate that haem-Fe is not solely responsible for oxidation and nitrosation reactions throughout an invitro digestion approach but its effect is promoted by a higher fat content in meat.

Heme-induced biomarkers associated with red meat promotion of colon cancer are not modulated by the intake of nitrite

Red and processed meat consumption is associated with the risk of colorectal cancer. Three hypotheses are proposed to explain this association, via heme-induced oxidation of fat, heterocyclic amines, or N-nitroso compounds. Rats have often been used to study these hypotheses, but the lack of enterosalivary cycle of nitrate in rats casts doubt on the relevance of this animal model to predict nitroso- and heme-associated human colon carcinogenesis. The present study was thus designed to clarify whether a nitrite intake that mimics the enterosalivary cycle can modulate heme-induced nitrosation and fat peroxidation. This study shows that, in contrast with the starting hypothesis, drinking water added with nitrite to mimic the salivary nitrite content did not change the effect of hemoglobin on biochemical markers linked to colon carcinogenesis, notably lipid peroxidation and cytotoxic activity in the colon of rat. However, ingested sodium nitrite increased fecal nitroso-compounds level, but their fecal concentration and their nature (iron-nitrosyl) would probably not be associated with an increased risk of cancer. We thus suggest that the rat model could be relevant for study the effect of red meat on colon carcinogenesis, in spite of the lack of nitrite in the saliva of rats.

Calcium and α-tocopherol suppress cured-meat promotion of chemically induced colon carcinogenesis in rats and reduce associated biomarkers in human volunteers

BACKGROUND

Processed meat intake has been associated with increased colorectal cancer risk. We have shown that cured meat promotes carcinogen-induced preneoplastic lesions and increases specific biomarkers in the colon of rats.

OBJECTIVES

We investigated whether cured meat modulates biomarkers of cancer risk in human volunteers and whether specific agents can suppress cured meat-induced preneoplastic lesions in rats and associated biomarkers in rats and humans.

DESIGN

Six additives (calcium carbonate, inulin, rutin, carnosol, α-tocopherol, and trisodium pyrophosphate) were added to cured meat given to groups of rats for 14 d, and fecal biomarkers were measured. On the basis of these results, calcium and tocopherol were kept for the following additional experiments: cured meat, with or without calcium or tocopherol, was given to dimethylhydrazine-initiated rats (47% meat diet for 100 d) and to human volunteers in a crossover study (180 g/d for 4 d). Rat colons were scored for mucin-depleted foci, putative precancer lesions. Biomarkers of nitrosation, lipoperoxidation, and cytotoxicity were measured in the urine and feces of rats and volunteers.

RESULTS

Cured meat increased nitroso compounds and lipoperoxidation in human stools (both P < 0.05). Calcium normalized both biomarkers in rats and human feces, whereas tocopherol only decreased nitro compounds in rats and lipoperoxidation in feces of volunteers (all P < 0.05). Last, calcium and tocopherol reduced the number of mucin-depleted foci per colon in rats compared with nonsupplemented cured meat (P = 0.01).

CONCLUSION

Data suggest that the addition of calcium carbonate to the diet or α-tocopherol to cured meat may reduce colorectal cancer risk associated with cured-meat intake. This trial was registered at clinicaltrials.gov as NCT00994526.

Calcium inhibits promotion by hot dog of 1,2-dimethylhydrazine-induced mucin-depleted foci in rat colon

Epidemiology suggests that processed meat is associated with colorectal cancer risk, but few experimental studies support this association. We have shown that a model of cured meat made in a pilot workshop promotes preneoplastic lesions, mucin-depleted foci (MDF) in the colon of rats. This study had two aims: to check if real store-bought processed meats also promote MDF, and to test if calcium carbonate, which suppresses heme-induced promotion, can suppress promotion by processed meat. A 14-day study was done to test the effect of nine purchased cured meats on fecal and urinary biomarkers associated with heme-induced carcinogenesis promotion. Fecal water from rats given hot dog or fermented raw dry sausage was particularly cytotoxic. These two cured meats were thus given to rats pretreated with 1,2-dimethylhydrazine, to evaluate their effect on colorectal carcinogenesis. After a 100-days feeding period, fecal apparent total N-nitroso compounds (ATNC) were assayed and colons were scored for MDF. Hot dog diet increased fecal ATNC and the number of MDF per colon compared with the no-meat control diet (3.0 ± 1.7 vs. 1.2 ± 1.4, p < 0.05). In a third study, addition of calcium carbonate (150 µmol/g) to the hot dog diet decreased the number of MDF/colon and fecal ATNC compared with the hot dog diet without calcium carbonate (1.2 ± 1.1 vs. 2.3 ± 1.4, respectively, p < 0.05). This is the first experimental evidence that a widely consumed processed meat promotes colon carcinogenesis in rats. It also shows that dietary prevention of this detrimental effect is possible.

Dietary patterns and risk of colorectal cancer in Tehran Province: a case-control study

Background

Colorectal cancer is the third and fourth leading cause of cancer incidence and mortality among men and women, respectively in Iran. However, the role of dietary factors that could contribute to this high cancer incidence remains unclear. The aim of this study was to determine major dietary patterns and its relationship with colorectal cancer.

Methods

This case–control study was conducted in four hospitals in Tehran city of Iran. A total of 71 patients (35 men and 36 women, aged 40–75 years) with incident clinically confirmed colorectal cancer (CRC) and 142 controls (70 men and 72 women, aged 40–75 years) admitted to hospital for acute, non-neoplastic diseases were recruited and interviewed. Dietary data were assessed by 125-item semi-quantitative food frequency questionnaire. Multivariate logistic regression was used to estimate the relationship between dietary patterns and risk of colorectal cancer.

Results

Two major dietary patterns (Healthy pattern and Western pattern) were derived using principal component analysis. Each dietary pattern explained 11.9% (Healthy pattern) and 10.3% (Western pattern) of the variation in food intake, respectively. After adjusting for confounding factors, the Healthy dietary pattern was significantly associated with a decreased risk of colorectal cancer (OR= 0.227; 95% CI=0.108–0.478) while an increased risk of colorectal cancer was observed with the Western dietary pattern (OR=2.616; 95% CI= 1.361-5.030).

Conclusion

Specific dietary patterns, which include healthy and western patterns, may be associated with the risk of colorectal cancer. This diet-disease relationship can be used for developing interventions that aim to promote healthy eating for the prevention of chronic disease, particularly colorectal cancer in the Iranian population.

Red meat and poultry intakes and risk of total and cause-specific mortality: results from cohort studies of Chinese adults in Shanghai

Most previous studies of meat intake and total or cause-specific mortality were conducted in North America, whereas studies in other areas have been limited and reported inconsistent results. This study investigated the association of red meat or poultry intake with risk of total and cause-specific mortality, including cancer and cardiovascular disease (CVD), in two large population-based prospective cohort studies of 134,290 Chinese adult women and men in Shanghai. Meat intakes were assessed through validated food frequency questionnaires administered in person at baseline. Vital status and dates and causes of deaths were ascertained through annual linkage to the Shanghai Vital Statistics Registry and Shanghai Cancer Registry databases and home visits every 2-3 years. Cox regression was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for the risk of death associated with quintiles of meat intake. During 803,265 person-years of follow up for women and 334,281 person-years of follow up for men, a total of 4,210 deaths in women and 2,733 deaths in men accrued. The median intakes of red meat were 43 g/day among women and 54 g/day among men, and pork constituted at least 95% of total meat intake for both women and men. Red meat intake was associated with increased total mortality among men, but not among women; the HR (95% CI) comparing the highest with the lowest quintiles were 1.18 (1.02-1.35) and 0.92 (0.82-1.03), respectively. This sex difference was statistically significant (P = 0.01). Red meat intake was associated with increased risk of ischemic heart disease mortality (HR = 1.41, 95% CI = 1.05-1.89) and with decreased risk of hemorrhagic stroke mortality (HR = 0.62, 95% CI = 0.45-0.87). There were suggestive inverse associations of poultry intake with risk of total and all-CVD mortality among men, but not among women. Further investigations are needed to elucidate the sex-specific associations between red meat intake and mortality.

Dietary meat and fat intake and prevalence of rhinoconjunctivitis in pregnant Japanese women: baseline data from the Kyushu Okinawa Maternal and Child Health Study

Background

Dietary fat exerts numerous complex effects on proinflammatory and immunologic pathways. Several epidemiological studies have examined the relationships between intake of fatty acids and/or foods high in fat and allergic rhinitis, but have provided conflicting findings. The current cross-sectional study investigated such relationships in Japan.

Methods

Study subjects were 1745 pregnant women. The definition of rhinoconjunctivitis was based on criteria from the International Study of Asthma and Allergies in Childhood. Information on dietary factors was collected using a validated self-administered diet history questionnaire. Adjustment was made for age; gestation; region of residence; number of older siblings; number of children; smoking; secondhand smoke exposure at home and at work; family history of asthma, atopic eczema, and allergic rhinitis; household income; education; and body mass index.

Results

The prevalence of rhinoconjunctivitis in the past 12 months was 25.9%. Higher meat intake was significantly associated with an increased prevalence of rhinoconjunctivitis: the adjusted odds ratio between extreme quartiles was 1.71 (95% confidence interval: 1.25-2.35, P for trend = 0.002). No measurable association was found between fish intake and rhinoconjunctivitis. Intake of total fat, saturated fatty acids, monounsaturated fatty acids, n-3 polyunsaturated fatty acids, α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, n-6 polyunsaturated fatty acids, linoleic acid, arachidonic acid, and cholesterol and the ratio of n-3 to n-6 polyunsaturated fatty acid intake were not evidently related to the prevalence of rhinoconjunctivitis.

Conclusions

The current results suggest that meat intake may be positively associated with the prevalence of rhinoconjunctivitis in young adult Japanese women.

Protection by Salvia extracts against oxidative and alkylation damage to DNA in human HCT15 and CO115 cells

DNA damage induced by oxidative and alkylating agents contributes to carcinogenesis, leading to possible mutations if replication proceeds without proper repair. However, some alkylating agents are used in cancer therapy due to their ability to induce DNA damage and subsequently apoptosis of tumor cells. In this study, the genotoxic effects of oxidative hydrogen peroxide (H₂O₂) and alkylating agents N-methyl-N-nitrosourea (MNU) and 1,3-bis-(2-chloroethyl)-1-nitosourea (BCNU) agents were examined in two colon cell lines (HCT15 and CO115). DNA damage was assessed by the comet assay with and without lesion-specific repair enzymes. Genotoxic agents were used for induction of DNA damage in both cell lines. Protective effects of extracts of three Salvia species, Salvia officinalis (SO), Salvia fruticosa (SF), and Salvia lavandulifolia (SL), against DNA damage induced by oxidative and alkylating agents were also determined. SO and SF protected against oxidative DNA damage in HCT15 cells. SO and SL decreased DNA damage induced by MNU in CO115 cells. In addition to chemopreventive effects of sage plant extracts, it was also important to know whether these plant extracts may interfere with alkylating agents such as BCNU used in cancer therapy, decreasing their efficacy. Our results showed that sage extracts tested and rosmarinic acid (RA), the main constituent, protected CO115 cells from DNA damage induced by BCNU. In HCT15 cells, only SF induced a reduction in BCNU-induced DNA damage. Sage water extracts and RA did not markedly change DNA repair protein expression in either cell line. Data showed that sage tea protected colon cells against oxidative and alkylating DNA damage and may also interfere with efficacy of alkylating agents used in cancer therapy.

Large prospective investigation of meat intake, related mutagens, and risk of renal cell carcinoma

BACKGROUND

The evidence for meat intake and renal cell carcinoma (RCC) risk is inconsistent. Mutagens related to meat cooking and processing, and variation by RCC subtype may be important to consider.

OBJECTIVE

In a large US cohort, we prospectively investigated intake of meat and meat-related compounds in relation to risk of RCC, as well as clear cell and papillary RCC histologic subtypes.

DESIGN

Study participants (492,186) completed a detailed dietary assessment linked to a database of heme iron, heterocyclic amines (HCA), polycyclic aromatic hydrocarbons (PAHs), nitrate, and nitrite concentrations in cooked and processed meats. Over 9 (mean) y of follow-up, we identified 1814 cases of RCC (498 clear cell and 115 papillary adenocarcinomas). HRs and 95% CIs were estimated within quintiles by using multivariable Cox proportional hazards regression.

RESULTS

Red meat intake [62.7 g (quintile 5) compared with 9.8 g (quintile 1) per 1000 kcal (median)] was associated with a tendency toward an increased risk of RCC [HR: 1.19; 95% CI: 1.01, 1.40; P-trend = 0.06] and a 2-fold increased risk of papillary RCC [P-trend = 0.002]. Intakes of benzo(a)pyrene (BaP), a marker of PAHs, and 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP), an HCA, were associated with a significant 20-30% elevated risk of RCC and a 2-fold increased risk of papillary RCC. No associations were observed for the clear cell subtype.

CONCLUSIONS

Red meat intake may increase the risk of RCC through mechanisms related to the cooking compounds BaP and PhIP. Our findings for RCC appeared to be driven by strong associations with the rarer papillary histologic variant. This study is registered at clinicaltrials.gov as NCT00340015.

Meat consumption and risk of lung cancer among never-smoking women

The relationship between diet and lung cancer, apart from the protective effect of fruit and vegetables, is poorly understood. Reports on the role of dietary components such as meat are inconsistent, and few studies include sufficient numbers of nonsmokers. We examined the relationship between meat consumption and never-smoking lung cancer in a hospital-based case-control study of Singapore Chinese women, a population with low smoking prevalence. Three hundred and ninety-nine cases and 815 controls were recruited, of whom 258 cases and 712 controls were never smokers. A standardized questionnaire (which included a food frequency questionnaire module) was administered by trained interviewers. Among these never smokers, fruit and vegetable intake were inversely associated with lung cancer risk. Seventy-two percent of meat consumed was white meat (chicken or fish). Meat consumption overall was inversely associated with lung cancer [adjusted odds ratio (OR), 0.88, 0.59 for second, third tertiles, P (trend) = .012]. An inverse relationship between fish consumption and lung cancer (adjusted OR, 0.81, 0.47 for 2nd, 3rd tertiles, P (trend) < .001) was observed. No association was seen between consumption of processed meats and lung cancer, nor between dietary heterocyclic amines and lung cancer. Our data suggest that fish consumption may be protective against lung cancer in never smokers.

The struggle within: microbial influences on colorectal cancer

Recently, an unprecedented effort has been directed at understanding the interplay between chronic inflammation and development of cancer, with the case of inflammatory bowel disease (IBD)-associated colorectal cancer at the forefront of this research endeavor. The last decade has been particularly fertile, with the discovery of numerous innovative paradigms linking various inflammatory, proliferative, and innate and adaptive immune signaling pathways to the development of colorectal cancer. Because of the preponderant role of the intestinal microbiota in the initiation and progression of IBD, recent efforts have been directed at understanding the relationship between bacteria and colorectal cancer. The microbiota and its collective genome, the microbiome, form a diverse and complex ecological community that profoundly impacts intestinal homeostasis and disease states. This review will discuss the differential influence of the microbiota on the development of IBD-associated colorectal cancer and highlight the role of innate immune sensor-dependent as well as -independent mechanisms in this pathology.

Trends in meat consumption in the USA

OBJECTIVE

To characterize the trends, distribution, potential determinants and public health implications of meat consumption within the USA.

DESIGN

We examined temporal trends in meat consumption using food availability data from the FAO and US Department of Agriculture (USDA), and further evaluated the meat intake by type (red, white, processed) in the National Health and Nutrition Examination Surveys (NHANES) linked to the MyPyramid Equivalents Database (MPED).

RESULTS

Overall meat consumption has continued to rise in the USA and the rest of the developed world. Despite a shift towards higher poultry consumption, red meat still represents the largest proportion of meat consumed in the USA (58 %). Twenty-two per cent of the meat consumed in the USA is processed. According to the NHANES 2003-2004, total meat intake averaged 128 g/d. The type and quantities of meat reported varied by education, race, age and gender.

CONCLUSIONS

Given the plausible epidemiological evidence for red and processed meat intake in cancer and chronic disease risk, understanding the trends and determinants of meat consumption in the USA, where meat is consumed at more than three times the global average, should be particularly pertinent to researchers and other public health professionals aiming to reduce the global burden of chronic disease.

Both base excision repair and O6-methylguanine-DNA methyltransferase protect against methylation-induced colon carcinogenesis

Methylating agents are widely distributed environmental carcinogens. Moreover, they are being used in cancer chemotherapy. The primary target of methylating agents is DNA, and therefore, DNA repair is the first-line barrier in defense against their toxic and carcinogenic effects. Methylating agents induce in the DNA O(6)-methylguanine (O(6)MeG) and methylations of the ring nitrogens of purines. The lesions are repaired by O(6)-methylguanine-DNA methyltransferase (Mgmt) and by enzymes of the base excision repair (BER) pathway, respectively. Whereas O(6)MeG is well established as a pre-carcinogenic lesion, little is known about the carcinogenic potency of base N-alkylation products such as N3-methyladenine and N3-methylguanine. To determine their role in cancer formation and the role of BER in cancer protection, we checked the response of mice with a targeted gene disruption of Mgmt or N-alkylpurine-DNA glycosylase (Aag) or both Mgmt and Aag, to azoxymethane (AOM)-induced colon carcinogenesis, using non-invasive mini-colonoscopy. We demonstrate that both Mgmt- and Aag-null mice show a higher colon cancer frequency than the wild-type. With a single low dose of AOM (3 mg/kg) Aag-null mice showed an even stronger tumor response than Mgmt-null mice. The data provide evidence that both BER initiated by Aag and O(6)MeG reversal by Mgmt are required for protection against alkylation-induced colon carcinogenesis. Further, the data indicate that non-repaired N-methylpurines are not only pre-toxic but also pre-carcinogenic DNA lesions.

Homologous recombination protects mammalian cells from replication-associated DNA double-strand breaks arising in response to methyl methanesulfonate

DNA-methylating agents of the S(N)2 type target DNA mostly at ring nitrogens, producing predominantly N-methylated purines. These adducts are repaired by base excision repair (BER). Since defects in BER cause accumulation of DNA single-strand breaks (SSBs) and sensitize cells to the agents, it has been suggested that some of the lesions on their own or BER intermediates (e.g. apurinic sites) are cytotoxic, blocking DNA replication and inducing replication-mediated DNA double-strand breaks (DSBs). Here, we addressed the question of whether homologous recombination (HR) or non-homologous end-joining (NHEJ) or both are involved in the repair of DSBs formed following treatment of cells with methyl methanesulfonate (MMS). We show that HR defective cells (BRCA2, Rad51D and XRCC3 mutants) are dramatically more sensitive to MMS-induced DNA damage as measured by colony formation, apoptosis and chromosomal aberrations, while NHEJ defective cells (Ku80 and DNA-PK(CS) mutants) are only mildly sensitive to the killing, apoptosis-inducing and clastogenic effects of MMS. On the other hand, the HR mutants were almost completely refractory to the formation of sister chromatid exchanges (SCEs) following MMS treatment. Since DSBs are expected to be formed specifically in the S-phase, we assessed the formation and kinetics of repair of DSBs by γH2AX quantification in a cell cycle specific manner. In the cytotoxic dose range of MMS a significant amount of γH2AX foci was induced in S, but not G1- and G2-phase cells. A major fraction of γH2AX foci colocalized with 53BP1 and phosphorylated ATM, indicating they are representative of DSBs. DSB formation following MMS treatment was also demonstrated by the neutral comet assay. Repair kinetics revealed that HR mutants exhibit a significant delay in DSB repair, while NHEJ mutants completed S-phase specific DSB repair with a kinetic similar to the wildtype. Moreover, DNA-PKcs inhibition in HR mutants did not affect the repair kinetics after MMS treatment. Overall, the data indicate that agents producing N-alkylpurines in the DNA induce replication-dependent DSBs. Further, they show that HR is the major pathway of protection of cells against DSB formation, killing and genotoxicity following S(N)2-alkylating agents.

Meat processing and colon carcinogenesis: cooked, nitrite-treated, and oxidized high-heme cured meat promotes mucin-depleted foci in rats

Processed meat intake is associated with colorectal cancer risk, but no experimental study supports the epidemiologic evidence. To study the effect of meat processing on carcinogenesis promotion, we first did a 14-day study with 16 models of cured meat. Studied factors, in a 2 x 2 x 2 x 2 design, were muscle color (a proxy for heme level), processing temperature, added nitrite, and packaging. Fischer 344 rats were fed these 16 diets, and we evaluated fecal and urinary fat oxidation and cytotoxicity, three biomarkers of heme-induced carcinogenesis promotion. A principal component analysis allowed for selection of four cured meats for inclusion into a promotion study. These selected diets were given for 100 days to rats pretreated with 1,2-dimethylhydrazine. Colons were scored for preneoplastic lesions: aberrant crypt foci (ACF) and mucin-depleted foci (MDF). Cured meat diets significantly increased the number of ACF/colon compared with a no-meat control diet (P = 0.002). Only the cooked nitrite-treated and oxidized high-heme meat significantly increased the fecal level of apparent total N-nitroso compounds (ATNC) and the number of MDF per colon compared with the no-meat control diet (P < 0.05). This nitrite-treated and oxidized cured meat specifically increased the MDF number compared with similar nonnitrite-treated meat (P = 0.03) and with similar nonoxidized meat (P = 0.004). Thus, a model cured meat, similar to ham stored aerobically, increased the number of preneoplastic lesions, which suggests colon carcinogenesis promotion. Nitrite treatment and oxidation increased this promoting effect, which was linked with increased fecal ATNC level. This study could lead to process modifications to make nonpromoting processed meat.

MGMT Ile143Val polymorphism, dietary factors and the risk of breast, colorectal and prostate cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk study

O(6)-Methylguanine-DNA methyltransferase (MGMT) repairs DNA damage caused by alkylating agents including N-nitroso compounds from diet. MGMT Ile143Val polymorphism may lead to less DNA damage repair and increased cancer risk depending on the environmental exposures. We investigated interactions between dietary factors and the MGMT Ile143Val polymorphism in relation to breast, colorectal and prostate cancer risk. There were 276/1498, 273/2984 and 312/1486 cases/controls for the breast, colorectal and prostate cancer studies respectively; all nested within the EPIC-Norfolk study, a prospective cohort of approximately 25,000 men and women aged 40-79. Baseline 7-day food diary data were collected for dietary assessment. MGMT Ile143Val polymorphism was not overall associated with breast, colorectal and prostate cancer risk. There was a significant interaction between this polymorphism and intake of red and processed meat on colorectal cancer risk (P(interaction)=0.04) suggesting an increased risk among carriers of the variant genotype compared to the MGMT Ile143Ile common genotype. A lower colorectal cancer risk was seen with higher intake of vitamin E and carotene among the variant genotype group but not in the common genotype group (P(interaction)=0.009 and P(interaction)=0.005 for vitamin E and carotene, respectively). A higher prostate cancer risk was seen with higher alcohol intake among the variant genotype (OR=2.08, 95% CI=1.21-3.57, P(interaction)=0.0009) compared to the common genotype with lower alcohol intake. In this UK population, the MGMT Ile143Val polymorphism was not overall associated with breast, colorectal and prostate cancer risk. There was evidence for this polymorphism playing a role in modulating the risk of prostate cancer in presence of alcohol. For colorectal cancer, the MGMT Ile143Val polymorphism may confer increased or decreased risk depending on the dietary exposure.

Construction of an N-nitroso database for assessing dietary intake

Dietary N-nitroso compounds are carcinogens synthesized during food processing from two main classes of precursors, oxides of nitrogen and amines or amides. Quantification of the dietary intake of N-nitroso compounds is significant to human cancers, including those of the stomach and upper gastro-intestinal tract, colon, and brain. Previous studies investigating these cancers primarily used proxy estimates of N-nitroso intake and not a full and complete database. In this report, we describe the development of a database to be used in conjunction with a food frequency questionnaire (FFQ) or twenty-four hour dietary records. Published analytical data for N-nitroso compounds were compiled and evaluated for inclusion in the database. The final database consisted of 23 different N-nitroso compounds for 500 foods from 39 different food subgroups. Next, database foods were matched to foods in a standard FFQ by imputation, or calculated value, or assumed zero. Using the FFQ modified with N-nitroso values, we evaluated the ability to compute N-nitroso intakes for a sample of healthy control subjects of cancer epidemiological studies. N-nitroso content of food items ranged from <0.01μg/100 g. to 142 μg/100 g and the richest sources were sausage, smoked meats, bacon, and luncheon meats. The database is useful to quantify N-nitroso intake for observational and epidemiological studies.

Survey of health attitudes and behaviors of a chiropractic college population

OBJECTIVES

We gathered information about health behaviors on a chiropractic campus, including compliance with recent guidelines for exercise as well as diet, smoking, and binge drinking. We also assessed the perceived importance of the chiropractic physician in role modeling and teaching healthy behaviors to patients.

METHODS

A survey instrument composed of 16 questions was designed and distributed to 279 students, faculty, and staff at a chiropractic college campus in northern California. Confidentiality was maintained throughout the process, and a response rate of 92% was obtained. Statistical analysis was performed on the data collected.

RESULTS

The levels of obesity, inactivity, and smoking on this college campus are lower than the levels reported for the metropolitan area, the state, and the nation. The level of binge drinking among our students was high but similar to the reported rates for college students generally. We found interesting and significant relationships between the behaviors of physical activity and diet (red meat consumption), obesity, and self-reported perceived health in our surveyed chiropractic college population. Without exception, all surveyed members of our campus community view doctors of chiropractic as having a responsibility to role model healthy behaviors and to educate their patients with regard to healthy behaviors; however, we also found that less importance was placed on role modeling and patient education by those who were obese or who consumed red meat in excess.

CONCLUSIONS

This chiropractic college campus places a high level of importance on both educating patients and role modeling healthy behaviors. In the behavioral domain, the rates of smoking, obesity, and inactivity are lower than what is seen in the general population. However, there remains room for considerable improvement to bring actual health behaviors closer in line with evidence-informed behavioral health practices.

A prospective study of meat and fat intake in relation to small intestinal cancer

Diets high in red and processed meats are associated with carcinogenesis of the large intestine, but no prospective study has examined meat and fat intake in relation to cancer of the small intestine. We prospectively investigated meat and fat intakes, estimated from a food frequency questionnaire, in relation to small intestinal cancer among half a million men and women enrolled in the NIH-AARP Diet and Health Study. We used Cox proportional hazards regression to estimate hazard ratios (HR) and 95% confidence intervals (95% CI). During up to 8 years of follow-up, 60 adenocarcinomas and 80 carcinoid tumors of the small intestine were diagnosed. Despite slightly elevated HRs for red meat, there were no clear associations for red or processed meat intake and either adenocarcinoma or carcinoid tumors of the small intestine. In contrast, we noted a markedly elevated risk for carcinoid tumors of the small intestine with saturated fat intake in both the categorical (highest versus lowest tertile: HR, 3.18; 95% CI, 1.62-6.25) and continuous data (HR, 3.72; 95% CI, 1.79-7.74 for each 10-g increase in intake per 1,000 kcal). Our findings suggest that the positive associations for meat intake reported in previous case-control studies may partly be explained by saturated fat intake.

Mouse models for the study of colon carcinogenesis

The study of experimental colon carcinogenesis in rodents has a long history, dating back almost 80 years. There are many advantages to studying the pathogenesis of carcinogen-induced colon cancer in mouse models, including rapid and reproducible tumor induction and the recapitulation of the adenoma-carcinoma sequence that occurs in humans. The availability of recombinant inbred mouse panels and the existence of transgenic, knock-out and knock-in genetic models further increase the value of these studies. In this review, we discuss the general mechanisms of tumor initiation elicited by commonly used chemical carcinogens and how genetic background influences the extent of disease. We will also describe the general features of lesions formed in response to carcinogen treatment, including the underlying molecular aberrations and how these changes may relate to the pathogenesis of human colorectal cancer.

A prospective study of red and processed meat intake in relation to cancer risk

BACKGROUND

Red meat and processed meat have been associated with carcinogenesis at several anatomic sites, but no prospective study has examined meat intake in relation to a range of malignancies. We investigated whether red or processed meat intake increases cancer risk at a variety of sites.

METHODS AND FINDINGS

The National Institutes of Health (NIH)-AARP (formerly the American Association for Retired Persons) Diet and Health Study is a cohort of approximately 500,000 people aged 50-71 y at baseline (1995-1996). Meat intake was estimated from a food frequency questionnaire administered at baseline. Cox proportional hazards regression was used to estimate hazard ratios and 95% confidence intervals within quintiles of red and processed meat intake. During up to 8.2 y of follow-up, 53,396 incident cancers were ascertained. Statistically significant elevated risks (ranging from 20% to 60%) were evident for esophageal, colorectal, liver, and lung cancer, comparing individuals in the highest with those in the lowest quintile of red meat intake. Furthermore, individuals in the highest quintile of processed meat intake had a 20% elevated risk for colorectal and a 16% elevated risk for lung cancer.

CONCLUSIONS

Both red and processed meat intakes were positively associated with cancers of the colorectum and lung; furthermore, red meat intake was associated with an elevated risk for cancers of the esophagus and liver.

Risk assessment models to estimate cancer probabilities

Cancer risk has become a significant research topic due to an increase in statistical risk models built to predict cancer incidence or mortality. Over the past 3 years, 15 models on the development of different types of cancer, including breast, colorectal, prostate, gastric, lung, ovarian, pancreatic, testicular, and skin, have been published. Risk assessment models are dynamic; they need to be updated as often as risks are discovered or changed. Not only are cancer risk models challenging to build, but, due to literacy-related issues, the cancer risk itself is challenging to communicate to the public. Clearly, guidelines outlining how to create valid and reliable risk assessment models are needed.

Cigarettes and alcohol in relation to colorectal cancer: the Singapore Chinese Health Study

The relations were examined between colorectal cancer and cigarette smoking and alcohol consumption within the Singapore Chinese Health Study, a population-based, prospective cohort of 63 257 middle-aged and older Chinese men and women enrolled between 1993 and 1998, from whom baseline data on cigarette smoking and alcohol consumption were collected through in-person interviews. By 31 December 2004, 845 cohort participants had developed colorectal cancer (516 colon cancer, 329 rectal cancer). Compared with nondrinkers, subjects who drank seven or more alcoholic drinks per week had a statistically significant, 72% increase in risk of colorectal cancer hazard ratio (HR)=1.72; 95% confidence interval (CI)=1.33-2.22). Cigarette smoking was associated with an increased risk of rectal cancer only. Compared with nonsmokers, HRs (95% CIs) for rectal cancer were 1.43 (1.10-1.87) for light smokers and 2.64 (1.77-3.96) for heavy smokers. Our data indicate that cigarette smoking and alcohol use interact in the Chinese population in an additive manner in affecting risk of rectal cancer, thus suggesting that these two exposures may share a common etiologic pathway in rectal carcinogenesis.

Effects of amino acid-derived luminal metabolites on the colonic epithelium and physiopathological consequences

Depending on the amount of alimentary proteins, between 6 and 18 g nitrogenous material per day enter the large intestine lumen through the ileocaecal junction. This material is used as substrates by the flora resulting eventually in the presence of a complex mixture of metabolites including ammonia, hydrogen sulfide, short and branched-chain fatty acids, amines; phenolic, indolic and N-nitroso compounds. The beneficial versus deleterious effects of these compounds on the colonic epithelium depend on parameters such as their luminal concentrations, the duration of the colonic stasis, the detoxication capacity of epithelial cells in response to increase of metabolite concentrations, the cellular metabolic utilization of these metabolites as well as their effects on colonocyte intermediary and oxidative metabolism. Furthermore, the effects of metabolites on electrolyte movements through the colonic epithelium must as well be taken into consideration for such an evaluation. The situation is further complicated by the fact that other non-nitrogenous compounds are believed to interfere with these various phenomenons. Finally, the pathological consequences of the presence of excessive concentrations of these compounds are related to the short- and, most important, long-term effects of these compounds on the rapid colonic epithelium renewing and homeostasis.

Human fecal water modifies adhesion of intestinal bacteria to Caco-2 cells

The aqueous phase of feces (fecal water) has been suggested to mediate the effects of diet on colon carcinogenesis. We determined whether human fecal water samples, of varying genotoxic potential, had the capacity to alter adhesion of intestinal bacteria to intestinal (Caco-2) cells. Genotoxicity of fecal water samples was measured using the single-cell gel electrophoresis assay ("comet" assay), and bacterial adhesion was measured using a well-established model system. Fecal water genotoxicity was found to correlate positively with inhibition of adhesion of Escherichia coli strains, Salmonella species, and Enterococcus faecium to Caco-2 cells. The presence of fecal water samples did not interfere with adhesion of Bacteroides and Lactobacillus species. Inhibition of adhesion by fecal water was not due to cytotoxicity to Caco-2 cells as cytotoxicities of most fecal water samples were similar, nor was the inhibitory effect due to bacteriotoxicity as toxicity of fecal waters in the 10 strains of bacteria studied was not detected. Results indicate that components in fecal water may alter adhesion of intestinal bacteria to intestinal cell surfaces and that this effect may be correlated to the genotoxic potential of fecal water. This may have consequences for dietary effects on colon carcinogenesis.

Meat and fish consumption, APC gene mutations and hMLH1 expression in colon and rectal cancer: a prospective cohort study (The Netherlands)

OBJECTIVE

The aim of this study was to investigate the associations between meat and fish consumption and APC mutation status and hMLH1 expression in colon and rectal cancer.

METHODS

The associations were investigated in the Netherlands Cohort Study, and included 434 colon and 154 rectal cancer patients on whom case-cohort analyses (subcohort n = 2948) were performed.

RESULTS

Total meat consumption was not associated with the endpoints studied. Meat product (i.e. processed meat) consumption showed a positive association with colon tumours harbouring a truncating APC mutation, whereas beef consumption was associated with an increased risk of colon tumours without a truncating APC mutation (incidence rate ratio (RR) highest versus lowest quartile of intake 1.61, 95% confidence interval (CI) 0.96-2.71, p-trend = 0.04 and 1.58, 95% CI 1.10-2.25, p-trend = 0.01, respectively). Consumption of other meat (horsemeat, lamb, mutton, frankfurters and deep-fried meat rolls) was associated with an increased risk of rectal cancer without a truncating APC mutation (RR intake versus no intake 1.79, 95% CI 1.10-2.90). No associations were observed for meat consumption and tumours lacking hMLH1 expression.

CONCLUSIONS

Our data indicate that several types of meat may contribute differently to the aetiology of colon and rectal cancer, depending on APC mutation status but not hMLH1 expression of the tumour.

Comparative analysis of tobacco-specific nitrosamines and total N-nitroso compounds in moldovan cigarette tobacco

While previous studies have evaluated levels of tobacco-specific nitrosamines (TSNA) and total N-nitroso compounds (NOC) in tobacco, there are no reports in the literature on TSNA and total NOC in the same tobacco products. We compared levels of TSNA, total NOC, and NOC precursors (NOCP) in tobacco of cigarettes purchased in Moldova and in some tobacco types commonly used for the manufacturing of Moldovan cigarettes. Cigarette tobaccos included those from non-Moldovan, traditional Moldovan, and blended Moldovan cigarettes. The results demonstrate that tobacco of non-Moldovan cigarettes contains higher TSNA and NOC levels (mean, 16 and 63 nmol/g tobacco, n = 6) than that of Moldovan cigarettes (mean, 5 and 23 nmol/g tobacco, n = 25). TSNA and NOC levels were also generally higher in tobacco of blended than in traditional Moldovan cigarettes. NOCP levels in Moldovan and non-Moldovan cigarette tobacco were similar as follows: 29000 +/- 30000 and 33000 +/- 28000 nmol/g tobacco (mean +/- SD). Total NOC were strongly correlated with total TSNA levels (r = 0.66; P < 0.0001). These findings demonstrate that current technologies involved in the manufacture of some blended cigarettes create conditions that favor N-nitrosation of alkaloids and other tobacco constituents.

Meat consumption and K-ras mutations in sporadic colon and rectal cancer in The Netherlands Cohort Study

Case–cohort analyses were performed on meat and fish consumption in relation to K-ras mutations in 448 colon and 160 rectal cancers that occurred during 7.3 years of follow-up, excluding the first 2.3 years, and 2948 subcohort members of The Netherlands Cohort Study on diet and cancer. Adjusted incidence rate ratios and 95% confidence intervals were computed for colon and rectal cancer and for K-ras mutation status subgroups. Total fresh meat, most types of fresh meat and fish were not associated with colon or rectal cancer, neither overall nor with K-ras mutation status. However, several weak associations were observed for tumours with a wild-type K-ras, including beef and colon tumours, and an inverse association for pork with colon and rectal tumours; for meat products, an increased association was observed with wild-type K-ras tumours in the colon and possibly with G>A transitions in rectal tumours.

Effects of culture with TNF-alpha, TGF-beta and insulin on sulphotransferase (SULT 1A1 and 1A3) activity in human colon and neuronal cell lines

The aim of the study was to determine whether the expression of sulphotransferase enzymes could be affected by the presence of cytokines or peptide hormones. The effects of cytokines (TNF-alpha and TGF-beta) and insulin on sulphotransferase (SULT 1A1 and 1A3) activity were studied in a human neuronal cell line (SK-N-SH) and a human gastrointestinal tract cell line (HT-29). Cells were cultured with varying concentrations of TNF-alpha, TGF-beta or insulin for 24 h; the SULT 1A1 isoform in the 2 cell lines showed different optimal substrate concentrations. There were no direct effects of cytokines on enzyme activity. Culture with TNF-alpha increased activity of both SULT 1A1 and 1A3 in the HT-29 cells; TGF-beta also increased activities of both isoforms but to a lesser extent; insulin increased activity of SULT 1A1 only. The cytokines and insulin had relatively little effect on sulphotransferase activity in the neuronal cell line. These results suggest that, unlike neuronal cells, gastrointestinal cells may respond to physiological states by altering sulphotransferase activity. As certain substrates such as diet-derived heterocyclic amines are bioactivated by sulphation to produce carcinogenic metabolites this may be a factor in the increased incidence of colorectal cancer in patients with inflammatory bowel disease or diabetes.

Diet and cancer prevention

Dietary effects are presumed to underlie many of the large international differences in incidence seen for most cancers. Apart from alcohol and a few micronutrients, however, the role of specific nutritional factors remains ill-defined. The evidence for a role of energy balance, physical inactivity, and obesity has strengthened, while for dietary fat it has weakened. Phytochemicals such as folate, lycopene and flavonoids are still the subject of active research. As the mechanisms underlying human carcinogenesis are better understood, dietary research will focus increasingly on intermediate markers such as the insulin-like growth factors and potentially carcinogenic metabolites.

A novel inflammation-related mouse colon carcinogenesis model induced by azoxymethane and dextran sodium sulfate

To develop an efficient animal model for colitis-related carcinogenesis, male Crj: CD-1 (ICR) mice were given a single intraperitoneal administration (10 mg/kg body weight) of a genotoxic colonic carcinogen, azoxymethane (AOM), and a 1-week oral exposure (2% in drinking water) to a non-genotoxic carcinogen, dextran sodium sulfate (DSS), under various protocols. At week 20, colonic neoplasms (adenocarcinomas, 100% incidence with 5.60 +/- 2.42 multiplicity; and adenomas, 38% incidence with 0.20 +/- 0.40 multiplicity) with dysplastic lesions developed in mice treated with AOM followed by DSS. Protocols in which AOM was given during or after DSS administration induced a few tubular adenomas or no tumors in the colon. Immunohistochemical investigation of such dysplasias and neoplasms revealed that all lesions were positive for beta-catenin, cyclooxygenase-2 and inducible nitric oxide synthase, but did not show p53 immunoreactivity. The results indicate that 1-week administration of 2% DSS after initiation with a low dose of AOM exerts a powerful tumor-promoting activity in colon carcinogenesis in male ICR mice, and may provide a novel mouse model for investigating colitis-related colon carcinogenesis and for identifying xenobiotics with modifying effects.