Meat consumption and the risk of incident distal colon and rectal adenoma

Mediterranean diet and colorectal adenomas: a systematic review and meta-analysis of observational studies

Colorectal adenomas (CRAs) are epithelial lesions of the large bowel that can develop into colorectal cancer. Some studies have shown an inverse association of the Mediterranean diet (MED) with adenoma, but the extent of the association is equivocal. Owing to the lack of meta-analytical evidence in the literature, we sought to assess the association between MED and CRAs by conducting a systematic review and meta-analysis. A comprehensive systematic literature search of observational studies was conducted via PubMed, Scopus, Google Scholar and Web of Sciences up to May 2023. Studies were included in our review if they evaluated the association between MED and CRA, following an observational study design. Six studies were included in this study. We found that adherence to MED was inversely associated with CRA risk (odds ratio, 0.79; confidence interval, 0.73-0.85); implying that higher adherence to MED could reduce the risk of CRA by ~21%. Stratification by the year of studies, sex, study design, country and exposure showed a significant association between MED and CRA. The results of the current study provide evidence of an inverse association between adherence to MED and CRAs.

Sex Difference of Colon Adenoma Pathway and Colorectal Carcinogenesis

Colorectal cancer (CRC) is one of the most common causes of cancer morbidity in both sexes but shows sex differences. First, sex-specific differences in tumor recurrence and survival rates have been reported. For example, the development of CRC is found about 1.5 times higher and 4-8 years earlier in males compared to females, suggesting the protective role of estrogen in the disease. Furthermore, female patients have a higher risk of developing right-sided (proximal) colon cancer than male patients, which is known to have more aggressive clinical character compared to left-sided (distal) colon cancer. That is, left and right CRCs show differences in carcinogenic mechanism, that the chromosomal instability pathway is more common in left colon cancer while the microsatellite instability and serrated pathways are more common in right colon cancer. It is thought that there are sex-based differences on the background of carcinogenesis of CRC. Sex differences of CRC have two aspects, sexual dimorphism (biological differences in hormones and genes) and gender differences (non-biological differences in societal attitudes and behavior). Recently, sex difference of colon adenoma pathway and sexual dimorphism in the biology of gene and protein expression, and in endocrine cellular signaling in the CRC carcinogenesis have been accumulated. In addition, behavioral patterns can lead to differences in exposure to risk factors such as drinking or smoking, diet and physical activity. Therefore, understanding sex/gender-related biological and sociocultural differences in CRC risk will help in providing strategies for screening, treatment and prevention protocols to reduce the mortality and improve the quality of life. In this review, sex/gender differences in colon adenoma pathway and various aspects such as clinicopathological, biological, molecular, and socio-cultural aspects of CRC were described.

Dietary patterns, untargeted metabolite profiles and their association with colorectal cancer risk

We investigated data-driven and hypothesis-driven dietary patterns and their association to plasma metabolite profiles and subsequent colorectal cancer (CRC) risk in 680 CRC cases and individually matched controls. Dietary patterns were identified from combined exploratory/confirmatory factor analysis. We assessed association to LC-MS metabolic profiles by random forest regression and to CRC risk by multivariable conditional logistic regression. Principal component analysis was used on metabolite features selected to reflect dietary exposures. Component scores were associated to CRC risk and dietary exposures using partial Spearman correlation. We identified 12 data-driven dietary patterns, of which a breakfast food pattern showed an inverse association with CRC risk (OR per standard deviation increase 0.89, 95% CI 0.80-1.00, p = 0.04). This pattern was also inversely associated with risk of distal colon cancer (0.75, 0.61-0.96, p = 0.01) and was more pronounced in women (0.69, 0.49-0.96, p = 0.03). Associations between meat, fast-food, fruit soup/rice patterns and CRC risk were modified by tumor location in women. Alcohol as well as fruit and vegetables associated with metabolite profiles (Q2 0.22 and 0.26, respectively). One metabolite reflecting alcohol intake associated with increased CRC risk, whereas three metabolites reflecting fiber, wholegrain, and fruit and vegetables associated with decreased CRC risk.

Distributions and Trends of the Global Burden of Colorectal Cancer Attributable to Dietary Risk Factors over the Past 30 Years

Dietary risk has always been a major risk factor for colorectal cancer (CRC). However, the contribution of dietary risk factors to CRC at the level of region, gender, and age has not been fully characterized. Based on the Global Burden of Disease (GBD) 2019 study, the death rates, age-standardized mortality rates (ASDRs), and estimated annual percentage changes (EAPCs) were calculated to assess the trends of CRC attributable to dietary risk factors over the past 30 years. Globally, the death cases of CRC increased to 1,085,797 in 2019, and the number of deaths attributed to dietary risk factors increased to 365,752 in 2019, representing approximately one-third of all CRC-related fatalities. Overall, the ASDR attributable to dietary risks was 4.61 per 100,000 in 2019, with a slight downward trend (EAPC = -0.29). Notably, there is a rising trend in early-onset colorectal cancer mortality associated with dietary factors. To alleviate CRC burdens, it is recommended to elevate the intake of whole grains, milk, calcium, and fiber while reducing consumption of red and processed meats. The results will improve the understanding, and provide guidance on the diet of CRC in different regions, gender, and age groups worldwide.

Dietary Xenobiotics Derived from Food Processing: Association with Fecal Mutagenicity and Gut Mucosal Damage

Whereas the mechanisms underlying the association of toxic dietary xenobiotics and cancer risk are not well established, it is plausible that dietary pattern may affect the colon environment by enhancing or reducing exposure to mutagens. This work aimed to investigate the association between xenobiotics intake and different stages of intestinal mucosal damage and colorectal cancer (CRC) screening and examine whether these associations may be mediated by altered intestinal mutagenicity. This was a case control study with 37 control subjects, 49 patients diagnosed with intestinal polyps, and 7 diagnosed with CRC. Lifestyle, dietary, and clinical information was registered after colonoscopy. For xenobiotics intake estimation the European Prospective Investigation into Cancer (EPIC) and the Computerized Heterocyclic Amines Resource for Research in Epidemiology of Disease (CHARRED) databases were used. The mutagenicity of fecal supernatants was assayed by the Ames test and light microscopy was used for the presence of aberrant crypt formation. Among all the potential carcinogens studied, the polyp group showed higher intakes of ethanol and dibenzo (a) anthracene (DiB(a)A). Besides, intakes between 0.75 and 1.29 µg/d of total polycyclic aromatic hydrocarbons (PAHs) were related with a higher risk of belonging to the polyp group. On the contrary, an intake of wholegrain cereals greater than 50 g/d was associated with a reduction in the relative risk of belonging to the polyp group. Heterocyclic amines (HAs) such as 2-amino-1-methyl-6-phenylimidazo (4,5,b) pyridine (PhIP) were associated with an increased level of mutagenicity in polyps. This study is of great interest for the identification of possible therapeutic targets for the early prevention of colon cancer through diet.

Association of Meat Subtypes With Colorectal Polyp Prevalence: Finding From the Lanxi Pre-colorectal Cancer Cohort in China

Background

Although the detrimental effect of red meat on colorectal cancer (CRC) incidence has been extensively reported, no previous studies have comprehensively linked different meat subtypes with colorectal polyp occurrence. The aim was to assess the association of meat and subtypes with colorectal polyp prevalence for the high-risk CRC Chinese population. Besides, we also focused on the association according to sizes, subsites, and multiplicity of polyps.

Methods

High-risk CRC patients aged 40–80 years were enrolled into the Lanxi Pre-colorectal Cancer Cohort (LP3C) between March 2018 and December 2019. Cross-sectional analyses were conducted by using the baseline data from LP3C. A validated food frequency questionnaire (FFQ) was employed to collect dietary information. Odds ratios (ORs) and 95% confidence intervals (95% CIs) of colorectal polyp prevalence were estimated by multivariate logistic regression.

Results

2,064 colorectal polyp cases were identified among 6,783 eligible participants in the survey of LP3C (March 2018 and December 2019). Total meat intake was positively related to rectum polyp prevalence (P_{for trend} = 0.01) but was not linked to total colorectal polyps after multivariable adjustment. For meat subtypes, higher poultry consumption was significantly related to a higher polyp prevalence [OR_Q4vs.Q1 (95% CI): 1.20 (1.02–1.42); P_{for trend} = 0.03]. Processed red meat intake was linked to an increased small polyp prevalence (P_{for trend} = 0.03) while unprocessed red meat had a relation with a higher rectum polyp prevalence (P_{for trend} = 0.04). Furthermore, seafood intake had a significant association with a higher multiple polyp prevalence [OR_Q4vs.Q1 (95% CI): 1.70 (1.31–2.21); P_{for trend} < 0.001].

Conclusion

The finding was that poultry meat consumption was related to a higher polyp prevalence. Besides, total meat consumption, processed and unprocessed red meat consumption, seafood consumption had a positive relation with certain polyp subtypes prevalence. Generally recommending reducing total meat consumption, including poultry, processed and unprocessed red meat, and seafood intake, may prevent colorectal polyps.

Association between Dietary Nitrate, Nitrite Intake, and Site-Specific Cancer Risk: A Systematic Review and Meta-Analysis

Background: People consume nitrates, nitrites, nitrosamines, and NOCs compounds primarily through processed food. Many studies have yielded inconclusive results regarding the association between cancer and dietary intakes of nitrates and nitrites. This study aimed to quantify these associations across the reported literature thus far. Methods: We performed a systematic review following PRISMA and MOOSE guidelines. A literature search was performed using Web of Science, Embase, PubMed, the Cochrane library, and google scholar up to January 2020. STATA version 12.0 was used to conduct meta-regression and a two-stage meta-analysis. Results: A total of 41 articles with 13 different cancer sites were used for analysis. Of these 13 cancer types/sites, meta-regression analysis showed that bladder and stomach cancer risk was greater, and that pancreatic cancer risk was lower with increasing nitrite intakes. Kidney and bladder cancer risk were both lower with increasing nitrate intakes. When comparing highest to lowest (reference) categories of intake, meta-analysis of studies showed that high nitrate intake was associated with an increased risk of thyroid cancer (OR = 1.40, 95% CI: 1.02, 1.77). When pooling all intake categories and comparing against the lowest (reference) category, higher nitrite intake was associated with an increased risk of glioma (OR = 1.12, 95% CI: 1.03, 1.22). No other associations between cancer risk and dietary intakes of nitrates or nitrites were observed. Conclusion: This study showed varied associations between site-specific cancer risks and dietary intakes of nitrate and nitrite. Glioma, bladder, and stomach cancer risks were higher and pancreatic cancer risk was lower with higher nitrite intakes, and thyroid cancer risk was higher and kidney cancer risk lower with higher nitrate intakes. These data suggest type- and site-specific effects of cancer risk, including protective effects, from dietary intakes of nitrate and nitrite.

The Role of Diet and Lifestyle in Early-Onset Colorectal Cancer: A Systematic Review

Simple Summary

This systematic review sifted through the exogenous dietary and lifestyle risk factors associated with early-onset colorectal cancer, going through the putative involvement of these exogenous risk factors in epigenetic and microbiota modifications. Given the burden of early-onset colorectal cancer and its globally increasing trend with scant literature on its pathogenesis, we believe it would be of benefit to highlight the importance of further systematic and large studies. Indeed, dietary and lifestyle modification could complement colorectal screening for early-onset colorectal cancer prevention.

Abstract

The incidence of early-onset colorectal cancer, defined as colorectal cancer occurring in young adults under the age of 50, is increasing globally. Knowledge of the etiological factors in young adults is far from complete. Questionable eoCRCs’ exogenous factors are represented by processed meat, sugary drinks, alcohol, Western dietary pattern, overweight and obesity, physical inactivity, and smoking, though with heterogeneous results. Therefore, we performed a systematic review to summarize the current evidence on the role of diet and lifestyle as eoCRC risk factors. We systematically searched PubMed, Scopus, and EMBASE up to July 2021, for original studies evaluating diet, alcohol, physical activity, BMI, and smoking in eoCRC and included twenty-six studies. Indeed, the exogenous factors could represent modifiable key factors, whose recognition could establish areas of future interventions through public health strategies for eoCRC primary prevention. Additionally, we discussed the role of additional non-modifiable risk factors, and of epigenetic regulation and microbiota as mediators of the eoCRC triggered by diet and lifestyle.

Colorectal Cancer and Diet: Risk Versus Prevention, Is Diet an Intervention?

Colorectal cancer is the third most common cause of cancer in men and women in the world. Epidemiologic research approximates that half of colon cancer risk is preventable by modifiable risk factors, including diet. This article reviews prior studies involving certain food items and their relation to colorectal cancer, to elucidate whether diet can be a potential intervention.

Selected Oxidative Stress Markers in Colorectal Cancer Patients in Relation to Primary Tumor Location-A Preliminary Research

Background and objectives: Ample evidence indicates that oxidative stress, including complex lipid peroxidation processes, may play a significant role in the pathogenesis of colorectal cancer. The goal of this study was to evaluate selected oxidative stress markers in patients with colorectal cancer depending on some clinical features, with particular attention paid to the location of the primary tumor. Materials and Methods: The study was conducted on a group of 66 patients with colorectal cancer. The study consisted of two stages. The first stage involved the analysis of medical records; the second consisted of determining selected oxidative stress markers by measuring malondialdehyde as well as total oxidant and antioxidant status. Results: Of all patients, 43 (65.15%) had colon cancer, of whom 30 (69.77%) had a tumor on the left side and 13 (30.23%) had a tumor on the right side of the colon. Of all the patients, 23 (34.85%) had rectal cancer. The mean total oxidant and antioxidant status was 809.76 (SD ± 392.65) µmol/L and 253.19 (233.33-310.66) µmol/L, respectively. The mean malondialdehyde serum level was 2478.04 (SD ± 1397.05) ng/mL. The mean malondialdehyde serum concentration in patients with primary tumors located on the right side was higher in a statistically significant way compared with the remaining patients. Conclusions: It was demonstrated that the intensity of lipid peroxidation processes is correlated with the development of colorectal cancer, particularly on the right side. The results should be interpreted rather cautiously due to certain limitations of the study.

Silencing NOB1 Can Affect Cell Proliferation and Apoptosis Via the C-Jun N-Terminal Kinase Pathway in Colorectal Cancer

OBJECTIVES

To investigate the bio-functions and the molecular mechanisms of NIN1/proteasome 26S subunit non-ATPase 8 binding protein 1 homolog (NOB1) in colorectal cancer cells.

METHODS

NOB1 expression was silenced using si-RNA in SW480 and LoVo cells. The transfection efficiency was measured by western blotting and RT-qPCR. Subsequently, the proliferation of SW480 and LoVo cells was determined using both MTT assay and colony-formation assay. Apoptosis and cell cycle analysis were determined using flow cytometry.

RESULTS

Compared with the normal control (NC) and scramble cells, si-NOB1 could significantly attenuate the proliferation, colony-formation ability and cell percentage of S stage (p < 0.05). Additionally, at the phosphorylation level, si-NOB1 could notably increase the expression of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and p38.

CONCLUSIONS

Inhibition of NOB1 expression suppressed the proliferation, and promoted the apoptosis through regulation of the JNK signaling pathway.

Levels and risk assessment of residual phthalates, polycyclic aromatic hydrocarbons and semi-volatile chlorinated organic compounds in toilet tissue papers

The presence of phthalates, polycyclic aromatic hydrocarbons (PAHs) and semi-volatile chlorinated organic compounds (SVCOC) in toilet tissue papers may be detrimental to the health of consumers upon exposure. This study therefore, sought to investigate the levels of these toxicants in toilet tissue papers on the Ghanaian market and the associated risk of exposure. The study also sought to conduct source apportionments for analytes.

A total of 32 composite toilet tissue samples from 8 different brands were analysed in replicates for PAHs, phthalates and SVCOCs. Analysis was conducted using Shimadzu GCMS QP 2020 with the MS operated in SIM mode.

The results showed elevated levels of PAHs, phthalates, and appreciable levels of SVCOCs in the toilets tissue papers. The risk assessment conducted, showed an associated elevated cancer risk >10⁻⁴ for PAHs in all samples and DEHP in samples NN, BB and SF. The risk associated with the levels of carcinogenic SVCOCs were found to be > 10^-5 but < 10⁻⁴.The hazard indices (HI) calculated for non-cancer effects, showed risk levels < 1.0 for phthalates in most toilet paper samples except for samples BB and SF. The HI recorded for chlorophenols were all <1.

Cumulatively, these values suggested elevated cancer and non-cancer risk associated with the dermal use of the toilet tissue papers on the Ghanaian market. The PCA-MLR source apportionment suggested two significant sources of SVOCs in the toilet tissue papers. PAHs, phthalates and 2-chloronaphthalene were of one source (oil base source) whereas SVCOCs were of another source (bleaching process).

Association between red and processed meat intake and colorectal adenoma incidence and recurrence: a systematic review and meta-analysis

The associations between red and processed meat intake and colorectal adenoma (CRA) incidence and recurrence are inconclusive. We performed a systematic review and meta-analysis to analysis these associations. We conducted a systematic search of PubMed, EMBASE and Web of Science up to December 2016. The relative risks (RRs) and 95% confidence intervals (CIs) were assessed. Subgroup analyses, dose-response-analyses, subtype analyses and analyses of CRA locations were also conducted. Twenty-seven studies that involved 208,117 participants and 19,150 cases met criteria. The RRs of the highest versus lowest intakes for CRA incidence were 1.23 (1.15–1.31) for red meat and 1.15 (1.07–1.24) for processed meat. Dose-response analyses for meat per 100 g/day yielded the results were consistent with the original analyses, with 1.14 (1.07–1.20) for red meat and 1.27 (1.03–1.50) for processed meat. Additionally, there were no associations between red and processed meat intake and CRA recurrence, including total CRA (P > 0.05), advanced CRA (P > 0.05) and multiple CRA (P > 0.05). In conclusion, our findings support the hypothesis that red and processed meat intake was associated with an increased CRA incidence but not for CRA recurrence.

The association of diet, gut microbiota and colorectal cancer: what we eat may imply what we get

Despite the success of colonoscopy screening and recent advances in cancer treatment, colorectal cancer (CRC) still remains one of the most commonly diagnosed and deadly cancers, with a significantly increased incidence in developing countries where people are adapting to Western lifestyle. Diet has an important impact on risk of CRC. Multiple epidemiological studies have suggested that excessive animal protein and fat intake, especially red meat and processed meat, could increase the risk of developing CRC while fiber could protect against colorectal tumorigenesis. Mechanisms have been investigated by animal studies. Diet could re-shape the community structure of gut microbiota and influence its function by modulating the production of metabolites. Butyrate, one of the short-chain fatty acids (SCFAs), which act as a favorable source for colonocytes, could protect colonic epithelial cells from tumorigenesis via anti-inflammatory and antineoplastic properties through cell metabolism, microbiota homeostasis, antiproliferative, immunomodulatory and genetic/epigenetic regulation ways. In contrast, protein fermentation and bile acid deconjugation, which cause damage to colonic cells through proinflammatory and proneoplastic ways, lead to increased risk of developing CRC. In conclusion, a balanced diet with an increased abundance of fiber should be adopted to reduce the risk and prevent CRC.

Colon Cancer: What We Eat

A higher incidence of colorectal cancer (CRC) is observed in Oceania and Europe, whereas Africa and Asia have a lower incidence. CRC is largely preventable by adapting a healthy lifestyle, such as healthy diet, adequate physical activity, and avoiding obesity. This review summarizes the latest work available, mainly epidemiologic studies, to examine the relationship between diet and CRC. Higher intake of red/processed meat could increase the CRC risk, whereas fibers, especially from whole grains and cereals, as well as fruit and vegetables may decrease the CRC risk. Heterogeneity and inconsistency among studies or individuals, however, need to be taken into consideration.

Red and processed meat consumption and colorectal cancer risk: a systematic review and meta-analysis

The associations between red and processed meat consumption and the risk of colorectal cancer types have not been conclusively defined. We performed a systematic review and meta-analysis to analyze these associations. We searched PubMed and EMBASE to identify studies published from inception through September 2016. Dose-response, subgroup and subtype analyses of colorectal cancer (colon cancer, proximal colon cancer, distal colon cancer and rectal cancer) were performed. We ultimately selected 60 eligible studies. Positive associations were observed for colorectal cancer in case-control studies (red meat, P<0.01; processed meat, P<0.01) and cohort studies (red meat, P<0.01; processed meat, P<0.01). However, subtype analyses yielded null results for distal colon cancer in case-control studies (P=0.41) and cohort studies (P=0.18) for red meat and null results for proximal colon cancer in case-control studies (P=0.13) and cohort studies (P=0.39) for processed meat. Additionally, although the results of case-control studies were positive (red meat, P<0.01; processed meat, P=0.04) for rectal cancer, there were no positive associations between red (P=0.34) and processed meat (P=0.06) consumption and the risk in cohort studies. In a systematic review and meta-analysis, we found consumption of red and processed meat was associated with the risk of overall colorectal cancer but not rectal cancer. Additionally, there were no associations between the consumption of red meat and distal colon cancer risk and between the consumption of processed meat and proximal colon cancer risk.

Health risk factors associated with meat, fruit and vegetable consumption in cohort studies: A comprehensive meta-analysis

The aim of this study was to perform a meta-analysis to test the association between red, processed, and total meat, as well as fruit and vegetable consumption, and selected health risk factors, including body weight status, smoking habit, physical activity level, level of education, and alcohol drinking in cohort studies on non-communicable disease. A systematic search of electronic databases was performed to identify relevant articles published up to March 2017. In a two-stage approach, frequency-weighted linear regression coefficients were first calculated for each variable, and then combined across studies through meta-regression. Ninety-eight studies including 20 on red meat, 6 on processed meat, 12 on total meat, 37 on fruit and vegetable combined, 21 on fruit and 24 on vegetable consumption were analyzed. Intake of red meat was positively associated with BMI, percentage of overweight and obese, low physical activity, and current and ever smoking and inversely associated with percentage of non-smokers and high physically active individuals. Similar associations were found for red meat were found, although based on fewer data. Intake of fruits and vegetables was positively associated with prevalence of non-smokers, high education and high physical activity, and similar results were found when examining fruit and vegetable consumption separately. Stratification by geographical area revealed that some associations were stronger in US rather than European or Asian cohorts. In conclusions, the distribution of health risk factors associated with high meat and fruit/vegetable consumption may differ from those of low-consumers. Some of these differences may mediate, confound, or modify the relation between diet and non-communicable disease risk.

Re-evaluation of potassium nitrite (E 249) and sodium nitrite (E 250) as food additives

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provided a scientific opinion re‐evaluating the safety of potassium nitrite (E 249) and sodium nitrite (E 250) when used as food additives. The ADIs established by the SCF (1997) and by JECFA (2002) for nitrite were 0–0.06 and 0–0.07 mg/kg bw per day, respectively. The available information did not indicate in vivo genotoxic potential for sodium and potassium nitrite. Overall, an ADI for nitrite per se could be derived from the available repeated dose toxicity studies in animals, also considering the negative carcinogenicity results. The Panel concluded that an increased methaemoglobin level, observed in human and animals, was a relevant effect for the derivation of the ADI. The Panel, using a BMD approach, derived an ADI of 0.07 mg nitrite ion/kg bw per day. The exposure to nitrite resulting from its use as food additive did not exceed this ADI for the general population, except for a slight exceedance in children at the highest percentile. The Panel assessed the endogenous formation of nitrosamines from nitrites based on the theoretical calculation of the NDMA produced upon ingestion of nitrites at the ADI and estimated a MoE > 10,000. The Panel estimated the MoE to exogenous nitrosamines in meat products to be < 10,000 in all age groups at high level exposure. Based on the results of a systematic review, it was not possible to clearly discern nitrosamines produced from the nitrite added at the authorised levels, from those found in the food matrix without addition of external nitrite. In epidemiological studies there was some evidence to link (i) dietary nitrite and gastric cancers and (ii) the combination of nitrite plus nitrate from processed meat and colorectal cancers. There was evidence to link preformed NDMA and colorectal cancers.

Re-evaluation of sodium nitrate (E 251) and potassium nitrate (E 252) as food additives

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provided a scientific opinion re-evaluating the safety of sodium nitrate (E 251) and potassium nitrate (E 252) when used as food additives. The current acceptable daily intakes (ADIs) for nitrate of 3.7 mg/kg body weight (bw) per day were established by the SCF (1997) and JECFA (2002). The available data did not indicate genotoxic potential for sodium and potassium nitrate. The carcinogenicity studies in mice and rats were negative. The Panel considered the derivation of an ADI for nitrate based on the formation of methaemoglobin, following the conversion of nitrate, excreted in the saliva, to nitrite. However, there were large variations in the data on the nitrate-to-nitrite conversion in the saliva in humans. Therefore, the Panel considered that it was not possible to derive a single value of the ADI from the available data. The Panel noticed that even using the highest nitrate-to-nitrite conversion factor the methaemoglobin levels produced due to nitrite obtained from this conversion would not be clinically significant and would result to a theoretically estimated endogenous N-nitroso compounds (ENOC) production at levels which would be of low concern. Hence, and despite the uncertainty associated with the ADI established by the SCF, the Panel concluded that currently there was insufficient evidence to withdraw this ADI. The exposure to nitrate solely from its use as a food additive was estimated to be less than 5% of the overall exposure to nitrate in food based on a refined estimated exposure scenario. This exposure did not exceed the current ADI (SCF, 1997). However, if all sources of exposure to dietary nitrate are considered (food additive, natural presence and contamination), the ADI would be exceeded for all age groups at the mean and the highest exposure.

Meat intake and risk of colorectal polyps: results from a large population-based screening study in Germany

Background: Red and processed meats have been shown to be associated with colorectal adenomas in many, but not all, studies, and the association according to the type of colorectal adenoma or the location in the colorectum is unclear.Objectives: We investigated the association of meat intake in relation to colorectal polyps and further investigated the association according to histologic subtypes and subsites in a large population-based screening study in Germany.Design: In this cross-sectional study, 15,950 participants aged ≥55 y underwent a screening colonoscopy. We calculated prevalence ratios (PRs) and 95% CIs for associations between meat intake and the most-advanced findings from a colonoscopy with the use of log binomial regression.Results: Overall, 3340 participants (20.4%) had nonadvanced adenomas, 1643 participants (10.0%) had advanced adenomas, and 189 participants (1.2%) had colorectal cancer. We observed no statistically significant association between red or processed meat consumption and the prevalence of any adenomas or advanced adenomas [highest compared with lowest: red meat, PR: 1.07 (95% CI: 0.83, 1.37); processed meat, PR: 1.11 (95% CI: 0.91, 1.36)]. In site-specific analyses, although no dose-response relation was observed, processed meat was positively associated with the prevalence of advanced adenomas in the rectum only (multiple times per day compared with <1 time/wk, PR: 1.87; 95% CI: 1.19, 2.95). Poultry intake was not associated with any outcome.Conclusions: On the basis of this large colonoscopy-based study, there are no significant associations between red or processed meat intake and the prevalence of any adenomas or advanced adenomas. However, processed meat may be positively associated with the prevalence of advanced adenomas in the rectum, but prospective cohort studies are needed to further clarify this association. There is no association between poultry consumption and the prevalence of colorectal polyps in this study.

Dietary Intake of Meat Cooking-Related Mutagens (HCAs) and Risk of Colorectal Adenoma and Cancer: A Systematic Review and Meta-Analysis

Much evidence suggests that the positive association between meat intake and colorectal adenoma (CRA) and cancer (CRC) risk is mediated by mutagenic compounds generated during cooking at high temperature. A number of epidemiological studies have estimated the effect of meat-related mutagens intake on CRC/CRA risk with contradictory and sometimes inconsistent results. A literature search was carried out (PubMed, Web of Science and Scopus) to identify articles reporting the relationship between the intake of meat-related mutagens (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5-f] quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f] quinoxaline: DiMeIQx, benzo(a) pyrene (B(a)P) and "meat derived mutagenic activity" (MDM)) and CRC/CRA risk. A random-effect model was used to calculate the risk association. Thirty-nine studies were included in the systematic review and meta-analysis. Polled CRA risk (15229 cases) was significantly increased by intake of PhIP (OR = 1.20; 95% CI: 1.13,1.28; p < 0.001), MeIQx (OR = 1.14; 95% CI: 1.05,1.23; p = 0.001), DiMeIQx (OR = 1.13; 95% CI: 1.05,1.21; p = 0.001), B(a)P (OR = 1.10; 95% CI: 1.02,1.19; p = 0.017) and MDM (OR = 1.17; 95% CI: 1.07,1.28; p = 0.001). A linear and curvilinear trend was observed in dose-response meta-analysis between CRA risk in association with PhIP, MDM, and MeIQx. CRC risk (21,344 cases) was increased by uptake of MeIQx (OR = 1.14; 95% CI: 1.04,1.25; p = 0.004), DiMeIQx (OR = 1.12; 95% CI: 1.02,1.22; p = 0.014) and MDM (OR = 1.12; 95% CI: 1.06,1.19; p < 0.001). No publication bias could be detected, whereas heterogeneity was in some cases rather high. Mutagenic compounds formed during cooking of meat at high temperature may be responsible of its carcinogenicity.

Mechanisms Linking Colorectal Cancer to the Consumption of (Processed) Red Meat: A Review

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in the world. The vast majority of CRC cases have been linked to environmental causes rather than to heritable genetic changes. Over the last decades, epidemiological evidence linking the consumption of red and, more convincingly, of processed red meat to CRC has accumulated. In parallel, hypotheses on carcinogenic mechanisms underlying an association between CRC and the intake of red and processed red meat have been proposed and investigated in biological studies. The hypotheses that have received most attention until now include (1) the presence of polycyclic aromatic hydrocarbons and heterocyclic aromatic amines, two groups of compounds recognized as carcinogenic, (2) the enhancing effect of (nitrosyl)heme on the formation of carcinogenic N-nitroso compounds and lipid peroxidation. However, none of these hypotheses completely explains the link between red and processed red meat intake and the CRC risk. Consequently, scientists have proposed additional mechanisms or refined their hypotheses. This review first briefly summarizes the development of CRC followed by an in-depth overview and critical discussion of the different potential carcinogenic mechanisms underlying the increased CRC risk associated with the consumption of red and processed red meat.

Human T lymphocytes bioactivate heterocyclic aromatic amines by forming DNA adducts

Heterocyclic aromatic amines (HAA) are formed in cooked meat, poultry and fish but also arise in tobacco smoke and exhaust gases. HAA are potential human carcinogens, which require metabolic activation to exert their genotoxicity. Human tissues can bioactivate HAA to produce reactive intermediates that bind to DNA. HAA DNA adduct formation occurs in human hepatocytes; however, the potential of HAA to form DNA adducts has not been investigated in human T lymphocytes. In this study, we investigated the ability of human T lymphocytes activated with PMA/Ionomycin or CD3/CD28 to express functional CYP1 activity and bioactivate three major HAA: 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), and 2-amino-9H-pyrido[2,3-b]indole (AαC) to form DNA adducts. Adducts were measured by ultraperformance liquid chromatography-electrospray ionization/multistage scan mass spectrometry. The highest level of DNA adducts occurred for AαC (16 adducts per 10⁹ nucleotides), followed by PhIP (9 adducts per 10⁹ nucleotides). In contrast, DNA adducts formed from MeIQx and the structurally related aromatic amine 4-aminobiphenyl, a known human carcinogen, were below the limit of detection (< 3 adducts per 10⁹ nucleotides). Moreover, we demonstrate that AαC is a potent inducer of CYP1A1 and CYP1B1 activity through a transcriptional mechanism involving the AhR pathway. Overall, our results highlight the capacity of activated human T lymphocytes to more efficiently bioactivate AαC to form DNA adducts than other prominent HAA or 4-ABP. Environ. Mol. Mutagen. 57:656-667, 2016. © 2016 Wiley Periodicals, Inc.

Foods and their components promoting gastrointestinal cancer

PURPOSE OF REVIEW

Cancer represents one of the most feared diseases. Despite an increasing number of available scientific data, most people remain unaware of those basic dietary and healthy lifestyle measures, which might reduce their risk to develop cancer. Environmental factors, diet, and lifestyle play a crucial role in the development of several different neoplastic diseases, particularly gastrointestinal cancer. In this article, we aimed at focusing on foods and their components able to increase gastrointestinal cancer risk.

RECENT FINDINGS

During the last few years, major emphasis has been addressed on the relation between red meat and gastrointestinal cancer. Many potential mechanisms linked red meat consumption and cancer risk, including heterocyclic amines, polycyclic aromatic hydrocarbons, N-nitroso compounds, and heme iron. Other chemical substances, contaminating food, such as acrylamide, showed gastrointestinal carcinogenic properties.

SUMMARY

Correct diet and lifestyle are clinically relevant strategies in preventing gastrointestinal cancer. In the fight against cancer, nutritional educative intervention programs are necessary to spread the knowledge on healthy eating and appropriate nutrition to reduce cancer risk.

δ- and γ-tocopherols inhibit phIP/DSS-induced colon carcinogenesis by protection against early cellular and DNA damages

Tocopherols, the major forms of vitamin E, are a family of fat-soluble compounds that exist in alpha (α-T), beta (β-T), gamma (γ-T), and delta (δ-T) variants. A cancer preventive effect of vitamin E is suggested by epidemiological studies. However, past animal studies and human intervention trials with α-T, the most active vitamin E form, have yielded disappointing results. A possible explanation is that the cancer preventive activity of α-T is weak compared to other tocopherol forms. In the present study, we investigated the effects of δ-T, γ-T, and α-T (0.2% in diet) in a novel colon cancer model induced by the meat-derived dietary carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and promoted by dextran sodium sulfate (DSS)-induced colitis in CYP1A-humanized (hCYP1A) mice. PhIP/DSS treatments induced multiple polypoid tumors, mainly tubular adenocarcinomas, in the middle to distal colon of the hCYP1A mice after 10 wk. Dietary supplementation with δ-T and γ-T significantly reduced colon tumor formation and suppressed markers of oxidative and nitrosative stress (i.e., 8-oxo-dG and nitrotyrosine) as well as pro-inflammatory mediators (i.e., NF-κB p65 and p-STAT3) in tumors and adjacent tissues. By administering δ-T at different time periods, we obtained results suggesting that the inhibitory effect of δ-T against colon carcinogenesis is mainly due to protection against early cellular and DNA damages caused by PhIP. α-T was found to be ineffective in inhibiting colon tumors and less effective in attenuating the molecular changes. Altogether, we demonstrated strong cancer preventive effects of δ-T and γ-T in a physiologically relevant model of human colon cancer. © 2016 Wiley Periodicals, Inc.

Heme Iron Intake, Dietary Antioxidant Capacity, and Risk of Colorectal Adenomas in a Large Cohort Study of French Women

BACKGROUND

Nitrosylated and non-nitrosylated heme iron from red processed and nonprocessed meat have been associated with increased colorectal carcinogenesis. Mechanisms include oxidative processes. It has been hypothesized that dietary antioxidants could counteract the effects of heme iron. We investigated the relationships between heme iron intake and the risk of colorectal adenomas, and a potential interaction with the dietary antioxidant capacity, in the E3N prospective cohort study.

METHODS

The study included 17,397 women, who underwent at least one colonoscopy. Among them, 1,409 were diagnosed with at least one first colorectal adenoma during the 103,253 person-years of follow-up. Dietary intake was measured by a semiquantitative food history questionnaire. HR estimates and 95% confidence intervals (CI) were obtained from Cox proportional hazards models, adjusted for potential confounders.

RESULTS

Heme iron intake was positively associated with colorectal and colon adenoma risks [HR for the fourth vs. first quartile: HR4 = 1.36 (1.13-1.65), Ptrend = 0.001 and HR4 = 1.49; 95% CI, 1.19-1.87; Ptrend = 0.0003, respectively]. Nonnitrosylated and nitrosylated heme iron intakes were, respectively, associated with advanced distal and proximal adenoma risks. There was a dose-effect relationship between the heme iron to total dietary antioxidant capacity ratio and colorectal adenoma risk.

CONCLUSION

In this prospective cohort study, the association between heme iron and colorectal adenoma risk was found to depend on site, nitrosylation or not, and the ratio with the NEAC.

IMPACT

These results emphasize the need for a global assessment of diet when considering nutritional prevention of colorectal carcinogenesis. Cancer Epidemiol Biomarkers Prev; 25(4); 640-7. ©2016 AACR.

Sex- and gender-specific disparities in colorectal cancer risk

Colorectal cancer is one of the most common causes of cancer morbidity both in men and in women. However, females over 65 years old show higher mortality and lower 5-year survival rate of colorectal cancer compared to their age-matched male counterparts. The objective of this review is to suggest gender-based innovations to improve colorectal cancer outcomes in females. Women have a higher risk of developing right-sided (proximal) colon cancer than men, which is associated with more aggressive form of neoplasia compared to left-sided (distal) colon cancer. Despite differences in tumor location between women and men, most of scientific researchers do not consider sex specificity for study design and interpretation. Also, colorectal cancer screening guidelines do not distinguish females from male, which may explain the higher frequency of more advanced neoplasia when tumors are first detected and false negative results in colonoscopy in females. Moreover, socio-cultural barriers within females are present to delay screening and diagnosis. Few studies, among studies that included both men and women, have reported sex-specific estimates of dietary risk factors which are crucial to establish cancer prevention guidelines despite sex- and gender-associated differences in nutrient metabolism and dietary practices. Furthermore, anti-cancer drug use for colorectal cancer treatment can cause toxicity to the reproductive system, and gender-specific recurrence and survival rates are reported. Therefore, by understanding sex- and gender-related biological and socio-cultural differences in colorectal cancer risk, gender-specific strategies for screening, treatment and prevention protocols can be established to reduce the mortality and improve the quality of life.

Sex- and gender-specific disparities in colorectal cancer risk

Colorectal cancer is one of the most common causes of cancer morbidity both in men and in women. However, females over 65 years old show higher mortality and lower 5-year survival rate of colorectal cancer compared to their age-matched male counterparts. The objective of this review is to suggest gender-based innovations to improve colorectal cancer outcomes in females. Women have a higher risk of developing right-sided (proximal) colon cancer than men, which is associated with more aggressive form of neoplasia compared to left-sided (distal) colon cancer. Despite differences in tumor location between women and men, most of scientific researchers do not consider sex specificity for study design and interpretation. Also, colorectal cancer screening guidelines do not distinguish females from male, which may explain the higher frequency of more advanced neoplasia when tumors are first detected and false negative results in colonoscopy in females. Moreover, socio-cultural barriers within females are present to delay screening and diagnosis. Few studies, among studies that included both men and women, have reported sex-specific estimates of dietary risk factors which are crucial to establish cancer prevention guidelines despite sex- and gender-associated differences in nutrient metabolism and dietary practices. Furthermore, anti-cancer drug use for colorectal cancer treatment can cause toxicity to the reproductive system, and gender-specific recurrence and survival rates are reported. Therefore, by understanding sex- and gender-related biological and socio-cultural differences in colorectal cancer risk, gender-specific strategies for screening, treatment and prevention protocols can be established to reduce the mortality and improve the quality of life.

Prevention of colorectal cancer and dietary management

OBJECTIVES

This systematic review focuses on dietary and lifestyle risk factors for colorectal cancer (CRC) prevention and chemoprevention among high-risk populations.

METHODS AND MATERIALS

We searched PubMed for English-language articles about dietary components, lifestyle risk factors, and chemoprevention agents in relation to colorectal cancer and their references published from 1980 through 2013. We reviewed articles jointly for the most clinically important information, emphasizing randomized trials and meta-analyses where available.

RESULTS

There is convincing evidence that intake of garlic, vitamin B6 and magnesium, active living, maintaining a healthy weight and waist, avoiding or reducing red meat, alcohol, and smoking, as well as hormone replacement therapy among women may significantly protect against developing colorectal cancer. There is less consistent evidence for fruit and vegetable intake (fiber and folate), fish and Omega-3 fatty acids, selenium, dairy, calcium and vitamin D. For high-risk populations, aspirin have been shown to protect against the development of colonic adenomas and CRC, while a minimal effective dose remains unclear.

CONCLUSIONS

Colorectal cancer can be prevented in general population through dietary and lifestyle interventions, and aspirin may be a good choice of chemoprevention agent among high risk individuals.

Inhibition of β-catenin signalling promotes DNA damage elicited by benzo[a]pyrene in a model of human colon cancer cells via CYP1 deregulation

Deregulation of Wnt/β-catenin signalling plays an important role in the pathogenesis of colorectal cancer. Interestingly, this pathway has been recently implicated in transcriptional control of cytochrome P450 (CYP) family 1 enzymes, which are responsible for bioactivation of a number of dietary carcinogens. In the present study, we investigated the impact of inhibition of Wnt/β-catenin pathway on metabolism and genotoxicity of benzo[a]pyrene (BaP), a highly mutagenic polycyclic aromatic hydrocarbon and an efficient ligand of the aryl hydrocarbon receptor, which is known as a primary regulator of CYP1 expression, in cellular models derived from colorectal tumours. We observed that a synthetic inhibitor of β-catenin, JW74, significantly increased formation of BaP-induced DNA adducts in both colorectal adenoma and carcinoma-derived cell lines. Using the short interfering RNA (siRNA) targeting β-catenin, we then found that β-catenin knockdown in HCT116 colon carcinoma cells significantly enhanced formation of covalent DNA adducts by BaP and histone H2AX phosphorylation, as detected by (32)P-postlabelling technique and immunocytochemistry, respectively, and it also induced expression of DNA damage response genes, such as CDKN1A or DDB2. The increased formation of DNA adducts formed by BaP upon β-catenin knockdown corresponded with enhanced production of major BaP metabolites, as well as with an increased expression/activity of CYP1 enzymes. Finally, using siRNA-mediated knockdown of CYP1A1, we confirmed that this enzyme plays a major role in formation of BaP-induced DNA adducts in HCT116 cells. Taken together, the present results indicated that the siRNA-mediated inhibition of β-catenin signalling, which is aberrantly activated in a majority of colorectal cancers, modulated genotoxicity of dietary carcinogen BaP in colon cell model in vitro, via a mechanism involving up-regulation of CYP1 expression and activity.

Meat subtypes and their association with colorectal cancer: Systematic review and meta-analysis

Associations between specific red meat subtypes and risk of colorectal cancer (CRC) have been investigated in a number of epidemiological studies. However, no publication to date has summarised the overall epidemiological evidence. We conducted a systematic review and meta-analysis of prospective studies (cohort, nested case-control or case-cohort studies), which reported relative risk (RR) estimates and 95% confidence intervals (CI) for the association between intake of meat subtypes with colorectal, colon or rectal cancer or colorectal adenoma risk. PubMed and ISI Web of Science were searched up until August 1, 2014. Nineteen studies examined meat subtypes (5 beef, 5 pork, 2 lamb, 1 veal and 19 poultry) and associations with colorectal, colon or rectal cancer risk and 4 studies examined associations with adenoma risk (1 beef and 4 poultry). Comparing highest versus lowest intake, beef consumption was associated with an increased risk of CRC (RR = 1.11, 95% CI = 1.01 to 1.22) and colon cancer (RR = 1.24, 95% CI = 1.07 to 1.44), but no association was found with rectal cancer (RR = 0.95, 95% CI = 0.78 to 1.16). Higher consumption of lamb was also associated with increased risk of CRC (RR = 1.24, 95% CI = 1.08 to 1.44). No association was observed for pork (RR = 1.07, 95% CI = 0.90 to 1.27), but some between study heterogeneity was observed. No association was observed for poultry consumption and risk of colorectal adenomas or cancer. This meta-analysis suggests that red meat subtypes differ in their association with CRC and its sub sites. Further analysis of data from prospective cohort studies is warranted, especially regarding the role of pork.

Polymorphisms in the carcinogen detoxification genes CYB5A and CYB5R3 and breast cancer risk in African American women

PURPOSE

Cytochrome b 5 (encoded by CYB5A) and NADH cytochrome b 5 reductase (encoded by CYB5R3) detoxify aromatic and heterocyclic amine mammary carcinogens found in cigarette smoke. We hypothesized that CYB5A and CYB5R3 polymorphisms would be associated with breast cancer risk in women.

METHODS

We characterized the prevalence of 18 CYB5A and CYB5R3 variants in genomic DNA from African American (AfrAm) and Caucasian (Cauc) women from the Carolina Breast Cancer Study population (1,946 cases and 1,747 controls) and determined their associations with breast cancer risk, with effect modification by smoking.

RESULTS

A CYB5R3 variant, I1M+6T (rs8190370), was significantly more common in breast cancer cases (MAF 0.0238) compared with controls (0.0169, p = 0.039); this was attributable to a higher MAF in AfrAm cases (0.0611) compared with AfrAm controls (0.0441, p = 0.046; adjusted OR 1.41, CI 0.98-2.04; p = 0.062). When smoking was considered, I1M+6T was more strongly associated with breast cancer risk in AfrAm smokers (adjusted OR 2.10, 1.08-4.07; p = 0.028) compared with never smokers (OR = 1.21; 0.77-1.88; p for interaction = 0.176). I1M+6T and three additional CYB5R3 variants, -251T, I8-1676C, and *392C, as well as two CYB5A variants, 13G and I2-992T, were significantly more common in AfrAms compared with Caucs.

CONCLUSIONS

CYB5R3 I1M+6C>T should be considered in future molecular epidemiologic studies of breast cancer risk in AfrAms. Further, variants in CYB5A and CYB5R3 should be considered in the evaluation of other tumors in AfrAms that are associated with aromatic and heterocyclic amine exposures, to include prostate, bladder, and colon cancers.

Meat, dairy, and cancer

In 2007 the World Cancer Research Fund and American Institute for Cancer Research (WCRF/AICR) report judged that the evidence for an association between red and processed meat consumption and colorectal cancer was convincing. In addition, the effect of other animal products on cancer risk has been studied, and the WCRF/AICR report concluded that milk probably decreases the risk of colorectal cancer but diets high in calcium probably increase the risk of prostate cancer, whereas there was limited evidence for an association between milk and bladder cancer and insufficient evidence for other cancers. There are several potential mechanisms relating meat to cancer, including heterocyclic amines, polycyclic aromatic hydrocarbons, N-nitroso compounds, and heme iron. Although the evidence in favor of a link between red and processed meat and colorectal cancer is convincing, the relations with other cancers are unclear. In this review, we summarize cohort studies conducted by the National Cancer Institute on meat and dairy intake in relation to cancer since the 2007 WCRF/AICR report. We also report the findings of meta-analyses published since 2007.

Dietary iron, iron homeostatic gene polymorphisms and the risk of advanced colorectal adenoma and cancer

Dietary iron intake and variation in iron homeostasis genes may affect colorectal neoplasia risk. We conducted two nested case-control studies within the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial: one of advanced colorectal adenoma (1205 cases; 1387 controls) and one of colorectal cancer (370 cases; 401 controls). Iron intake was estimated with a food frequency questionnaire and genotyping was performed for 21 genes. Unconditional logistic regression was used to estimate odds ratio (OR) and 95% confidence intervals (95% CIs) for colorectal neoplasia risk within quartiles of intake. Several single nucleotide polymorphisms (SNPs) modified the association between iron intake and the risk of adenoma or cancer. Dietary iron was positively associated with colorectal adenoma among three SNPs of HEPHL1, including carriers of the AA genotype at rs7946162 (ORQ4-Q1 = 2.22, 95% CI 1.15-4.27, Ptrend = 0.03; Pinteraction = 0.10), the TT genotype at rs2460063 (ORQ4-Q1 = 2.39, 95% CI 1.26-4.54, Ptrend = 0.02; Pinteraction = 0.04) and the GG genotype at rs7127348 (ORQ4-Q1 = 2.40, 95% CI 1.23-4.67, Ptrend = 0.02; Pinteraction = 0.09). Heme iron was positively associated with colorectal cancer among those with GG genotypes for ACO1 rs10970985 (ORQ4-Q 1 = 2.45, 95% CI 3.40-8.06, Ptrend = 0.004; Pinteraction = 0.05). However, none of the associations were statistically significant after adjustment for multiple comparisons. Future studies should target the specific genes and SNPs for which the association was significant prior to multiple comparison correction.

Influence of dietary fat type on benzo(a)pyrene [B(a)P] biotransformation in a B(a)P-induced mouse model of colon cancer

In the US alone, around 60,000 lives/year are lost due to colon cancer. Diet and environment have been implicated in the development of sporadic colon tumors. The objective of this study was to determine how dietary fat potentiates the development of colon tumors through altered B(a)P biotransformation, using the Adenomatous polyposis coli with Multiple intestinal neoplasia mouse model. Benzo(a)pyrene was administered to mice through tricaprylin, and unsaturated (USF; peanut oil) and saturated (SF; coconut oil) fats at doses of 50 and 100 μg/kg via oral gavage over a 60-day period. Blood, colon, and liver were collected at the end of exposure period. The expression of B(a)P biotransformation enzymes [cytochrome P450 (CYP)1A1, CYP1B1 and glutathione-S-transferase] in liver and colon were assayed at the level of protein, mRNA and activities. Plasma and tissue samples were analyzed by reverse phase high-performance liquid chromatography for B(a)P metabolites. Additionally, DNA isolated from colon and liver tissues was analyzed for B(a)P-induced DNA adducts by the (32)P-postlabeling method using a thin-layer chromatography system. Benzo(a)pyrene exposure through dietary fat altered its metabolic fate in a dose-dependent manner, with 100 μg/kg dose group registering an elevated expression of B(a)P biotransformation enzymes, and greater concentration of B(a)P metabolites, compared to the 50 μg/kg dose group (P<.05). This effect was more pronounced for SF group compared to USF group (P<.05). These findings establish that SF causes sustained induction of B(a)P biotransformation enzymes and extensive metabolism of this toxicant. As a consequence, B(a)P metabolites were generated to a greater extent in colon and liver, whose concentrations also registered a dose-dependent increase. These metabolites were found to bind with DNA and form B(a)P-DNA adducts, which may have contributed to colon tumors in a subchronic exposure regimen.

Polycyclic aromatic hydrocarbons: determinants of urinary 1-hydroxypyrene glucuronide concentration and risk of colorectal cancer in the Shanghai Women's Health Study

Background

Associations between polycyclic aromatic hydrocarbons (PAHs) and colorectal cancer have been reported previously but few studies have characterized PAH exposure using biological measurements. We evaluated colorectal cancer risk in relation to urinary concentration of 1-hydroxypyrene glucuronide (1-OHPG), a polycyclic aromatic hydrocarbon (PAH) metabolite, and assessed determinants of PAH exposure among controls in the Shanghai Women’s Health Study (SWHS).

Methods

Concentrations of 1-OHPG were measured in spot urine samples collected from 343 colorectal cancer cases and 343 individually matched controls. Questionnaires were administered to collect information on demographic characteristics and reported exposures. Odds ratios were calculated for risk of colorectal cancer in relation to quartiles of urinary 1-OHPG concentration. Potential determinants of natural log-transformed urinary 1-OHPG concentration were evaluated among a combined sample of controls from this study and another nested case–control study in the SWHS (N_total=652).

Results

No statistically significant differences in risk of colorectal cancer by urinary 1-OHPG levels were observed. Among controls, the median (interquartile range) urinary 1-OHPG concentration was 2.01 pmol/mL (0.95-4.09). Active and passive smoking, using coal as a cooking fuel, eating foods that were cooked well done, and recent consumption of fried dough (e.g., yóutiáo) were associated with elevated levels of 1-OHPG, though only active smoking and fried dough consumption achieved statistical significance in multivariate analyses.

Conclusions

This study does not provide evidence of an association between urinary levels of 1-OHPG and risk of colorectal cancer among women. Several environmental and dietary sources of PAH exposure were identified. Overall, the levels of 1-OHPG in this population of predominantly non-smoking women were considerably higher than levels typically observed among non-smokers in Europe, North America, and other developed regions.

Prospective investigation of body mass index, colorectal adenoma, and colorectal cancer in the prostate, lung, colorectal, and ovarian cancer screening trial

PURPOSE

Obesity has consistently been linked to an increased risk of colorectal cancer, particularly among men. Whether body mass index (BMI) differentially influences the risk across the stages of colorectal cancer development remains unclear. We evaluated the associations of BMI with colorectal adenoma incidence, adenoma recurrence, and cancer in the context of a large screening trial, in which cases and controls had an equal chance for disease detection.

METHODS

We prospectively evaluated the association between baseline BMI and the risk of incident distal adenoma (1,213 cases), recurrent adenoma (752 cases), and incident colorectal cancer (966 cases) among men and women, ages 55 to 74 years, randomly assigned to receive flexible sigmoidoscopy screening as part of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. We calculated odds ratios (ORs) and 95% CIs for adenoma incidence and recurrence, and hazard ratios (HRs) and 95% CIs for colorectal cancer incidence, using multivariable-adjusted models.

RESULTS

Compared with normal-weight men (18.5 to 24.9 kg/m(2)), obese men (≥ 30 kg/m(2)) had significantly higher risk of incident adenoma (OR, 1.32; 95% CI, 1.06 to 1.65) and colorectal cancer (HR, 1.48; 95% CI, 1.16 to 1.89) and a borderline increased risk of recurrent adenoma (OR, 1.50; 95% CI, 0.98 to 2.30). No associations were observed for either adenoma or cancer in women.

CONCLUSION

Data from this large prospective study suggest that obesity is important throughout the natural history of colorectal cancer, at least in men, and colorectal cancer prevention efforts should encourage the achievement and maintenance of a healthy body weight in addition to regular screenings.

Combined genotoxic effects of a polycyclic aromatic hydrocarbon (B(a)P) and an heterocyclic amine (PhIP) in relation to colorectal carcinogenesis

Colorectal neoplasia is the third most common cancer worldwide. Environmental factors such as diet are known to be involved in the etiology of this cancer. Several epidemiological studies have suggested that specific neo-formed mutagenic compounds related to meat consumption are an underlying factor involved in the association between diet and colorectal cancer. Heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) are known mutagens and possible human carcinogens formed at the same time in meat during cooking processes. We studied the genotoxicity of the model PAH benzo(a)pyrene (B(a)P) and HCA 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), alone or in mixture, using the mouse intestinal cell line Apc^Min/+, mimicking the early step of colorectal carcinogenesis, and control Apc^+/+ cells. The genotoxicity of B(a)P and PhIP was investigated using both cell lines, through the quantification of B(a)P and PhIP derived DNA adducts, as well as the use of a genotoxic assay based on histone H2AX phosphorylation quantification. Our results demonstrate that heterozygous Apc mutated cells are more effective to metabolize B(a)P. We also established in different experiments that PhIP and B(a)P were more genotoxic on Apc^Min/+ cells compared to Apc^+/+. Moreover when tested in mixture, we observed a combined genotoxicity of B(a)P and PhIP on the two cell lines, with an increase of PhIP derived DNA adducts in the presence of B(a)P. Because of their genotoxic effects observed on heterozygous Apc mutated cells and their possible combined genotoxic effects, both B(a)P and PhIP, taken together, could be implicated in the observed association between meat consumption and colorectal cancer.

Differential response of flat and polypoid colitis-associated colorectal neoplasias to chemopreventive agents and heterocyclic amines

Individuals with ulcerative colitis face an increased risk of developing colorectal cancer and would benefit from early chemopreventive intervention. Results from preclinical studies in the mouse model of dextran sulfate sodium-induced colitis demonstrate that flat and polypoid colitis-associated dysplasias arise via distinct genetic pathways, impacted by the allelic status of p53. Furthermore, flat and polypoid dysplasias vary in their response to induction by the heterocyclic amine 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and inhibition by 5-aminosalicylic acid, a common therapy for the maintenance of colitis patients. These data suggest that use of combination therapy is essential for the optimal inhibition of colitis-associated colorectal cancer.