Intake of red meat and heterocyclic amines, metabolic pathway genes and bladder cancer risk

Polymorphisms in drug-metabolizing genes and urinary bladder cancer susceptibility and prognosis: Possible impacts and future management

Epidemiological studies have shown the association of genetic variants with risks of occupational and environmentally induced cancers, including bladder (BC). The current review summarizes the effects of variants in genes encoding phase I and II enzymes in well-designed studies to highlight their contribution to BC susceptibility and prognosis. Polymorphisms in genes codifying drug-metabolizing proteins are of particular interest because of their involvement in the metabolism of exogenous genotoxic compounds, such as tobacco and agrochemicals. The prognosis between muscle-invasive and non-muscle-invasive diseases is very different, and it is difficult to predict which will progress worse. Web of Science, PubMed, and Medline were searched to identify studies published between January 1, 2010, and February 2023. We included 73 eligible studies, more than 300 polymorphisms, and 46 genes/loci. The most studied candidate genes/loci of phase I metabolism were CYP1B1, CYP1A1, CYP1A2, CYP3A4, CYP2D6, CYP2A6, CYP3E1, and ALDH2, and those in phase II were GSTM1, GSTT1, NAT2, GSTP1, GSTA1, GSTO1, and UGT1A1. We used the 46 genes to construct a network of proteins and to evaluate their biological functions based on the Reactome and KEGG databases. Lastly, we assessed their expression in different tissues, including normal bladder and BC samples. The drug-metabolizing pathway plays a relevant role in BC, and our review discusses a list of genes that could provide clues for further exploration of susceptibility and prognostic biomarkers.

Big data and artificial intelligence in cancer research

The field of oncology has witnessed an extraordinary surge in the application of big data and artificial intelligence (AI). AI development has made multiscale and multimodal data fusion and analysis possible. A new era of extracting information from complex big data is rapidly evolving. However, challenges related to efficient data curation, in-depth analysis, and utilization remain. We provide a comprehensive overview of the current state of the art in big data and computational analysis, highlighting key applications, challenges, and future opportunities in cancer research. By sketching the current landscape, we seek to foster a deeper understanding and facilitate the advancement of big data utilization in oncology, call for interdisciplinary collaborations, ultimately contributing to improved patient outcomes and a profound understanding of cancer.

Long Follow-Up Times Weaken Observational Diet-Cancer Study Outcomes: Evidence from Studies of Meat and Cancer Risk

For years, prospective cohort studies of diet and cancer incidence have reported smaller effects than do retrospective case-control (CC) studies. The differences have been attributed to problems with CC studies, including dietary recall bias, poor matching of cases and controls, and confounding. The hypothesis evaluated here is that long follow-up periods between ascertainment of diet and cancer incidence weaken the findings. Prospective studies of cancer incidence with respect to serum 25-hydroxyvitamin D concentration have already shown reduced benefit of higher concentrations for longer follow-up periods. Evaluating that hypothesis for dietary factors involved searching the journal literature for meta-analyses of red meat and processed meat and cancer incidence. I used findings from observational studies for bladder, breast, colorectal, and gastric cancers. To evaluate the effect of duration of follow-up time, I used two approaches. First, I plotted the relative risks for CC studies for gastric cancer with respect to consumption of 100 g/day of red meat and for bladder cancer for 50 g/day of processed meat against the interval between the dietary data and cancer incidence. Second, I compared nested CC studies of meat and cancer incidence for five breast cancer studies and one colorectal cancer study. Both approaches yielded an inverse correlation between interval or follow-up time and relative risk. My findings strongly suggest that diet near time of cancer diagnosis is more important than for longer intervals, that results from meta-analyses should be revised when possible with appropriate adjustments for duration of follow-up, and that dietary guidelines be revised accordingly.

Genetic factors, adherence to healthy lifestyle behaviors, and risk of bladder cancer

BACKGROUND

Genetic and lifestyle factors both contribute to the pathogenesis of bladder cancer, but the extent to which the increased genetic risk can be mitigated by adhering to a healthy lifestyle remains unclear. We aimed to investigate the association of combined lifestyle factors with bladder cancer risk within genetic risk groups.

METHODS

We conducted a prospective study of 375 998 unrelated participants of European ancestry with genotype and lifestyle data and free of cancer from the UK biobank. We generated a polygenic risk score (PRS) using 16 single nucleotide polymorphisms and a healthy lifestyle score based on body weight, smoking status, physical activity, and diet. Cox models were fitted to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) of genetic and lifestyle factors on bladder cancer.

RESULTS

During a median follow-up of 11.8 years, 880 participants developed bladder cancer. Compared with those with low PRS, participants with intermediate and high PRS had a higher risk of bladder cancer (HR 1.29, 95% CI 1.07-1.56; HR 1.63, 95% CI 1.32-2.02, respectively). An optimal lifestyle was associated with an approximately 50% lower risk of bladder cancer than a poor lifestyle across all genetic strata. Participants with a high genetic risk and a poor lifestyle had 3.6-fold elevated risk of bladder cancer compared with those with a low genetic risk and an optimal lifestyle (HR 3.63, 95% CI 2.23 -5.91).

CONCLUSIONS

Adhering to a healthy lifestyle could substantially reduce the bladder cancer risk across all genetic strata, even for high-genetic risk individuals. For all populations, adopting an intermediate lifestyle is more beneficial than a poor one, and adhering to an optimal lifestyle is the ideal effective strategy for bladder cancer prevention.

Meat Intake and the Risk of Bladder Cancer: A Systematic Review and Meta-Analysis of Observational Studies

The evidence for the association between meat intake and the risk of bladder cancer (BC) is still inconclusive. A total of 29 studies involving 1,475,125 participants and 18,836 cases of BC were included in the meta-analysis. Among these studies, 11 reported total meat intake, 20 reported red meat intake, 19 reported processed meat intake, 15 reported white meat intake, and 15 reported fish intake. The results suggested that there was an overall increase in BC risk associated with total meat intake (RR = 1.10; 95% confidence interval: 0.92-1.31; I² = 55.20%; P = 0.014), and a higher red meat (RR = 1.23; 95% CI: 1.08-1.39; I² = 51.30%; P = 0.004) or processed meat (RR = 1.16; 95% CI: 1.08-1.25; I² = 28.00%; P = 0.125) intake may increase the risk of BC. In contrast, a higher intake of fish (RR = 0.80; 95% CI: 0.67-0.95; I² = 62.90%; P = 0.001) was inversely associated with the risk of BC. Moreover, we did not observe an association between white meat (RR = 0.96; 95% CI: 0.83-1.10; I² = 53.70%; P = 0.007) and the risk of BC. Our findings suggested that dietary intervention may be an effective approach to preventing BC, which still needs to be confirmed by further well-designed observational studies.

Dietary meat mutagens intake and cancer risk: A systematic review and meta-analysis

Background

Clinical and preclinical studies suggested that certain mutagens occurring as a reaction of creatine, amino acids, and sugar during the high temperature of cooking meat are involved in the pathogenesis of human cancer. Here we conducted a systematic review and meta-analysis to examine whether meat mutagens [PhIP, MeIQx, DiMeIQx, total HCA, and B(a)P] present a risk factor for human cancer.

Methods

We searched the following databases for relevant articles published from inception to 10 Oct 2021 with no language restrictions: Pubmed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), Baidu Academic, Zhejiang Digital Library. Two independent researchers screened all titles and obtained eligible texts for further screening. Independent data extraction was conducted, and meta-analysis was carried out using random-effects models to calculate the risk ratio of the meat mutagens exposure.

Results

A total of 1,786,410 participants and 70,653 cancer cases were identified. Among these, there were 12 different types of cancer at various sites, i.e., breast, bladder, colorectal, colon, rectum, prostate, lung, Non-Hodgkin lymphoma, kidney, gastric, esophagus, pancreatic, hepatocellular carcinoma. Cancer risk was significantly increased by intake of PhIP (OR = 1.13;95% CI 1.07–1.21; p < 0.001), MeIQx (OR = 1.14; 95% CI: 1.07–1.21; p < 0.001), DiMeIQx (OR = 1.07; 95% CI: 1.01–1.13; p = 0.013), total HCA (OR = 1.20; 95% CI: 1.03–1.38; p = 0.016), and cancer risk was not significantly increased by intake of B(a)P (OR = 1.04; 95% CI: 0.98–1.10; p = 0.206).

Conclusion

Meat mutagens of PhIP, MeIQx, DiMeIQx, and total HCA have a positive association with the risk of cancer.

Systematic review registration

[www.crd.york.ac.uk/prospero], identifier [CRD42022148856].

Dietary patterns and risk of bladder cancer: a systematic review and meta-analysis

BACKGROUND

Several studies have investigated the relationship between dietary patterns and the risk of bladder cancer (BC) in different regions including Europe, the United States, and Asia, with no conclusive evidence. A meta-analysis was undertaken to integrate the most recent information on the relationship between a data-driven Western diet (WD), the Mediterranean diet (MD), and dietary-inflammatory-index (DII) and the risk of BC.

METHOD

We looked for published research into the relationship between dietary patterns and the incidence of BC in the PubMed/Medline, Cochrane Library, Web of Science, and Scopus databases up until February 2021. Using a multivariate random-effects model, we compared the highest and lowest categories of WD, MD and DII patterns and provided the relative risk (RR) or odds ratios (OR) and 95 percent confidence intervals (CIs) for the relevant relationships.

RESULTS

The analysis comprised 12 papers that were found to be suitable after scanning the databases. Both case-control (OR 0.73, 95% CI: 0.52, 0.94; I2 = 49.9%, n = 2) and cohort studies (RR 0.93, 95% CI: 0.88, 0.97; I2 = 63%, n = 4) found a substantial inverse association between MD and BC. In addition, although cohort studies (RR 1.53, 95% CI 1.37, 1.70; I2 = 0%, n = 2) showed a direct association between WD and BC, case-control studies (OR 1.33, 95% CI 0.81, 1.88; I2 = 68.5%, n = 2) did not. In cohort studies, we found no significant association between DII and BC (RR 1.02, 95% CI 0.93, 1.12; I2 = 38.5%, n = 2). In case-control studies, however, a strong direct association between DII and BC was discovered (RR 2.04, 95% CI 1.23, 2.85; I2 = 0%, n = 2).

CONCLUSION

The current meta-analysis showed that MD and WD have protective and detrimental effects on BC risk, respectively. No significant association between DII and the risk of BC was observed. More research is still needed to confirm the findings. Additional study is warranted to better understand the etiological mechanisms underlying how different dietary patterns affect BC.

TRIAL REGISTRATION

Protocol registration number: CRD42020155353. Database for protocol registration: The international prospective register of systematic reviews database (PROSPERO). Data of registration: August 2020.

The association between meat and fish consumption and bladder cancer risk: a pooled analysis of 11 cohort studies

Evidence on the effects of meat consumption from different sources on the risk of bladder cancer (BC) is limited and controversial. Therefore, this study aimed to evaluate the associations between meat consumption and BC risk using a pooled data approach. Individual data from 11 prospective cohorts comprising 2848 BC cases and 515,697 non-cases with a total of 5,498,025 person-years of follow-up was pooled and analysed to investigate the potential associations between total red meat and products, red meat, processed meat, poultry and total fish and BC risk. Hazard ratios (HRs), with corresponding 95% confidence intervals (CIs), were estimated using Cox regression models stratified on cohort. Overall, an increased BC risk was found for high intake of organ meat (HR comparing highest with lowest tertile: 1.18, 95% CI: 1.03, 1.36, p-trend = 0.03). On the contrary, a marginally inverse association was observed for total fish intake and BC risk among men (HR comparing highest with lowest tertile: 0.79, 95% CI 0.65, 0.97, p-trend = 0.04). No associations were observed for other meat sources. Results of this prospective study suggest that organ meat consumption may be associated with BC development. Replication in large-scale prospective studies and investigation of possible causal mechanisms is needed.

Food consumption, meat cooking methods and diet diversity and the risk of bladder cancer

BACKGROUND

Since food metabolites are eliminated by the urinary tract, several studies have investigated the association between diet and bladder cancer risk. Recently, the World Cancer Research Fund International/American Institute for Cancer Research (WCRF/AICR) suggested a potential beneficial effect of some foods (mainly vegetables, fruit, and milk) in the development of bladder cancer. We investigated the association between food groups and bladder cancer risk, seeking insights into food diversity as well as meat cooking methods.

METHODS

Data were derived from an Italian multicentre case-control study, conducted between 2003 and 2014, including 690 bladder cancer cases and 665 frequency-matched controls. Odds ratios (ORs) and the corresponding 95% confidence intervals (95%CIs) for various dietary aspects were estimated by unconditional logistic regression models adjusted for energy intake and the major known risk factors for bladder cancer.

RESULTS

Comparing the highest versus the lowest quartiles, consumption of vegetables (OR = 0.62; 95%CI: 0.44-0.88) and milk/yogurt (OR = 0.62; 95%CI: 0.44-0.87) reduced the risk of bladder cancer. Conversely, consumption of meat increased bladder cancer risk with an OR of 1.57 (95%CI: 1.07-2.31), particularly when the meat was stewed (OR = 1.47; 95%CI: 1.03-2.09) or roasted (OR = 1.41; 95%CI: 1.00-1.99). There was a suggestion that a diversified diet reduced the risk of bladder cancer, but this was not significant.

CONCLUSIONS

Our study consolidates the role of diet in bladder cancer aetiology, showing a reduced risk for vegetable and milk/yogurt consumption and an increased risk for meat consumption, especially when the meat is stewed or roasted.

Processed Meat Intake and Bladder Cancer Risk in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cohort

BACKGROUND

The association between processed meat intake and bladder cancer risk has been evaluated by several observational studies with inconsistent results.

METHODS

In a cohort of 101,721 subjects in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, we analyzed the association of processed meat intake with bladder cancer risk.

RESULTS

After a median of 12.5 years of follow-up, 776 new cases of bladder cancer were identified. Intake of processed red meat was significantly associated with the incidence of bladder cancer after multivariate adjustment [highest vs. lowest quintile: HR, 1.47; 95% confidence interval (CI), 1.12-1.93; P _trend = 0.008]. In contrast, there was only a suggestive but not significant association between intake of total processed meat and bladder cancer risk after multivariable adjustment (highest vs. lowest quintile: HR, 1.16; 95% CI, 0.89-1.50; P _trend = 0.073).

CONCLUSIONS

This large prospective study suggests that intake of processed red meat is associated with a higher risk of bladder cancer.

IMPACT

Bladder cancer risk is increased with cumulative intake of processed red meat.

Bioactivation of the tobacco carcinogens 4-aminobiphenyl (4-ABP) and 2-amino-9H-pyrido[2,3-b]indole (AαC) in human bladder RT4 cells

Occupational and tobacco exposure to aromatic amines (AAs) including 4-aminobiphenyl (4-ABP) and 2-naphthylamine (2-NA) are associated with bladder cancer (BC) risk. Several epidemiological studies have also reported a possible role for structurally related heterocyclic aromatic amines (HAAs) formed in tobacco smoke or cooked meats with BC risk. We had screened for DNA adducts of 4-ABP, 2-NA, and several prominent HAAs formed in tobacco smoke or grilled meats including 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylmidazo[4,5-f]quinoxaline (MeIQx), and 2-amino-9H-pyrido[2,3-b]indole (AαC) in the bladder DNA of BC patients, using liquid chromatography/mass spectrometry. We detected DNA adducts of 4-ABP, but not adducts of the other carcinogens. In this study, we have examined the capacity of RT4 cells, an epithelial human bladder cell line, to bioactivate AAs and HAAs to DNA damaging agents, which may contribute to BC. 4-ABP and AαC formed DNA adducts, but DNA adducts of 2-NA, PhIP, and MeIQx were not detected. 4-ABP DNA adducts were formed at tenfold higher levels than AαC adducts. Pretreatment of RT4 cells with α-naphthoflavone (1-10 µM), a specific cytochrome P450 1 (CYP1) inhibitor, decreased AαC adduct formation by 50% but did not affect the level of 4-ABP adducts. However, cell pretreatment with 8-methoxypsoralen (0.1-1 µM), a potent inhibitor of CYP2A, resulted in a 90% decrease of 4-ABP DNA adducts levels. These data signify that CYP2A and CYP1A isoforms expressed in the target urothelium bioactivate 4-ABP and AαC, respectively, and may be a critical feature of aromatic amine-induced urinary bladder carcinogenesis. The bioactivation of other tobacco and environmental AAs by bladder CYPs and their ensuing bladder DNA damage warrants further study.

Targeted and Untargeted Detection of DNA Adducts of Aromatic Amine Carcinogens in Human Bladder by Ultra-Performance Liquid Chromatography-High-Resolution Mass Spectrometry

Epidemiological studies have linked aromatic amines (AAs) from tobacco smoke and some occupational exposures with bladder cancer risk. Several epidemiological studies have also reported a plausible role for structurally related heterocyclic aromatic amines present in tobacco smoke or formed in cooked meats with bladder cancer risk. DNA adduct formation is an initial biochemical event in bladder carcinogenesis. We examined paired fresh-frozen (FR) and formalin-fixed paraffin-embedded (FFPE) nontumor bladder tissues from 41 bladder cancer patients for DNA adducts of 4-aminobiphenyl (4-ABP), a bladder carcinogen present in tobacco smoke, and 2-amino-9 H-pyrido[2,3- b]indole, 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine and 2-amino-3,8-dimethylimidazo[4,5- f]quinoxaline, possible human carcinogens, which occur in tobacco smoke and cooked meats. These chemicals are present in urine of tobacco smokers or omnivores. Targeted DNA adduct measurements were done by ultra-performance liquid chromatography-electrospray ionization multistage hybrid Orbitrap MS. N-(2'-Deoxyguanosin-8-yl)-4-ABP ( N-(dG-C8)-4-ABP) was the sole adduct detected in FR and FFPE bladder tissues. Twelve subjects (29%) had N-(dG-C8)-4-ABP levels above the limit of quantification, ranging from 1.4 to 33.8 adducts per 109 nucleotides (nt). DNA adducts of other human AA bladder carcinogens, including 2-naphthylamine (2-NA), 2-methylaniline (2-MA), 2,6-dimethylaniline (2,6-DMA), and lipid peroxidation (LPO) adducts, were screened for in bladder tissue, by our untargeted data-independent adductomics method, termed wide-selected ion monitoring (wide-SIM)/MS2. Wide-SIM/MS2 successfully detected N-(dG-C8)-4-ABP, N-(2'-deoxyadenosin-8-yl)-4-ABP and the presumed hydrazo linked adduct, N-(2'-deoxyguanosin- N2-yl)-4-ABP, and several LPO adducts in bladder DNA. Wide-SIM/MS2 detected multiple DNA adducts of 2-NA, 2-MA, and, 2,6-DMA, when calf thymus DNA was modified with reactive intermediates of these carcinogens. However, these AA-adducts were below the limit of detection in unspiked human bladder DNA (<1 adduct per 108 nt). Wide-SIM/MS2 can screen for many types of DNA adducts formed with exogenous and endogenous electrophiles and will be employed to identify DNA adducts of other chemicals that may contribute to the etiology of bladder cancer.

Dietary patterns and risk of recurrence and progression in non-muscle-invasive bladder cancer

The association of dietary factors with urinary bladder cancer prognosis has scarcely been investigated, and results of studies conducted to date are inconsistent. We investigated whether empirically derived dietary patterns are associated with risks of recurrence and progression in non-muscle-invasive bladder cancer (NMIBC) patients. Data from 595 newly diagnosed NMIBC patients from an ongoing prospective cohort study were used to derive dietary patterns using exploratory factor analysis. Factor scores were calculated and then categorized in sex-specific tertiles. Multivariable-adjusted proportional hazards regression models were used to estimate hazard ratios and 95% confidence intervals for the associations between tertiles of adherence to the dietary patterns and risks of recurrence and progression. We identified four dietary patterns: "fruits and vegetables," "Western," "low-fat," and "Tex-Mex." Patients in the highest tertile of adherence to the Western pattern experienced a 1.48 times higher risk of recurrence (95% CI 1.06-2.06) compared to patients in the lowest tertile. No statistically significant associations of a Western diet with risk of progression or of the other dietary patterns with risk of recurrence and progression were found. Overall, we found that adherence to a Western diet was associated with a higher risk of recurrence but further studies are needed to confirm our findings.

Red and processed meat consumption and risk of bladder cancer: a dose-response meta-analysis of epidemiological studies

Background/objectives

Several epidemiological studies have analyzed the associations between red and processed meat and bladder cancer risk but the shape and strength of the associations are still unclear. Therefore, we conducted a dose–response meta-analysis to quantify the potential association between red and processed meat and bladder cancer risk.

Methods

Relevant studies were identified by searching the PubMed database through January 2016 and reviewing the reference lists of the retrieved articles. Results were combined using random-effects models.

Results

Five cohort studies with 3262 cases and 1,038,787 participants and 8 cases–control studies with 7009 cases and 27,240 participants met the inclusion criteria. Red meat was linearly associated with bladder cancer risk in case–control studies, with a pooled RR of 1.51 (95% confidence interval (CI) 1.13, 2.02) for every 100 g increase per day, while no association was observed among cohort studies (P heterogeneity across study design = 0.02). Based on both case–control and cohort studies, the pooled relative risk (RR) for every 50 g increase of processed meat per day was 1.20 (95% CI 1.06, 1.37) (P heterogeneity across study design = 0.22).

Conclusions

This meta-analysis suggests that processed meat may be positively associated with bladder cancer risk. A positive association between red meat and risk of bladder cancer was observed only in case–control studies, while no association was observe in prospective studies.

Electronic supplementary material

The online version of this article (doi:10.1007/s00394-016-1356-0) contains supplementary material, which is available to authorized users.

Effects of Maternal Diet During Pregnancy on the Risk of Childhood Acute Lymphoblastic Leukemia: A Systematic Review

Acute lymphoblastic leukemia (ALL) is the most common type of leukemia in children that can be affected by maternal diet. The aim of this study was to evaluate maternal dietary risk factors of ALL. We searched MEDLINE, Cochrane Library, Springer Link, Wiley Online, Science Direct, Mosby, ISI Web of Science, OVID, ProQuest, and Scopus from database inception until February 2, 2016. Two reviewers scanned titles, abstracts, and keywords of articles after excluding duplicates. We included case-control studies evaluating the relationship between maternal diet during pregnancy and childhood ALL. The search resulted in 2,940 papers, of which 11 full-text articles met the criteria for inclusion in the review and were analyzed. The finding of these studies suggest that maternal diet composed largely of vegetables, fruits, and protein sources before and during pregnancy can reduce the risk of ALL in offspring. Maternal alcohol intake had no effect. Nevertheless, inherent limitations of case-control studies like measurement error, random error, recall bias, and selection bias preclude conclusive evidence. Persuading pregnant women to follow a healthy diet rich in fruits, vegetables, and protein may reduce the risk of childhood ALL. Avoiding alcohol intake seems prudent.

Cancer in Japan: Prevalence, prevention and the role of heterocyclic amines in human carcinogenesis

In this article, three topics are being studied in order to understand the present state of cancer in Japan. First, the statistics on cancer mortality indicates that the mortality from cancer in young individuals has been decreasing during the last 50 years, although the total mortality from cancer has been steadily and steeply increasing. Second, epidemiological analyses of cancer causes in Japan indicated that 50 % of cancer cases are preventable, and that prevention of infection and refraining from tobacco smoking will reduce cancer mortality by about 40 %. Third, mutagenic/carcinogenic heterocyclic amines present in cooked meat/fish have been suggested to be carcinogenic in humans in many epidemiological studies carried out in Japan and other countries.

Dietary factors associated with bladder cancer

It is biologically plausible for dietary factors to influence bladder cancer risk considering that beneficial as well as harmful components of a diet are excreted through the urinary tract and in direct contact with the epithelium of the bladder. However, studies that investigated the association between dietary factors and bladder cancer (BC) risk have largely reported inconsistent results. The macronutrient intake and risk of BC could have yield inconsistent results across studies because of lack of details on the type, source and the quantities of different dietary fatty acids consumed. There is evidence to suggest that consumption of processed meat may increase BC risk. Dietary carbohydrate intake does not appear to be directly associated with BC risk. Even though a large number of studies have investigated the association between fruit/vegetable consumption/micronutrients in those and BC risk, they have yielded inconsistent results. Gender-specific subgroup analysis, details of how fruits and vegetables are consumed (raw vs. cooked), adequate control for smoking status/aggressiveness of the cancer and consideration of genetic make-up may clarify these inconsistent results. There is no strong evidence to suggest that supplementation with any common micronutrient is effective in reducing BC risk. These limitations in published research however do not totally eclipse the observation that a diet rich in fruits and vegetables and low in processed meat along with especially smoking cessation may convey some protective effects against BC risk.

Heterocyclic Aromatic Amines in Cooked Meat Products: Causes, Formation, Occurrence, and Risk Assessment

Meat products are sources of protein with high biological value and an essential source of other nutrients, such as vitamins and minerals. Heating processes cause food to become more appetizing with changes in texture, appearance, flavor, and chemical properties by the altering of protein structure and other ingredients. During heat treatment, heterocyclic aromatic amines (HAAs), potent mutagens/carcinogens, are formed due to the Maillard reaction. The HAAs are classified in at least 2 groups: thermic HAAs (100 to 300 °C) and pyrolytic HAAs (>300 °C). This review focuses on the parameters and precursors which affect the formation of HAAs: preparation, such as the marinating of meat, and cooking methods, including temperature, duration, and heat transfer, as well as levels of precursors. Additionally, factors are described subject to pH, and the type of meat and ingredients, such as added antioxidants, types of carbohydrates and amino acids, ions, fat, and other substances inhibiting or enhancing the formation of HAAs. An overview of the different analytical methods available is shown to determine the HAAs, including their preparation to clean up the sample prior to extraction. Epidemiological results and human daily intake of HAAs obtained from questionnaires show a relationship between the preference for very well-done meat products with increased HAA levels and an enhanced risk of the incidence of cancer, besides other carcinogens in the diet. The metabolic pathway of HAAs is governed by the activity of several enzymes leading to the formation of DNA adducts or HAA excretion and genetic sensitivity of individuals to the impact of HAAs on human cancer risk.

Red and processed meat intake and risk of bladder cancer: a meta-analysis

Findings from epidemiologic studies concerning red and processed meat intake and bladder cancer risk remain conflicting. Thus, we conducted this meta-analysis to examine the associations of red and processed meat intake with bladder cancer. Eligible studies published up to May 2014 were retrieved via both computer searches and review of references. Finally, we identified 14 studies on red meat (involving 9,084 cases) and 11 studies on processed meat (7,562 cases) involving up to 1,558,848 individuals. Random-effects models were used to estimate summary relative risk estimates (SRRE) based on high vs. low intake, and heterogeneity between study results was explored through stratified analyses on the basis of red/processed meat category, gender, study design and geographical region. Overall, the SRRE for all studies regarding red meat intake was 1.15 (95% CI: 0.97-1.36). Significant positive association was observed between processed meat consumption and bladder cancer (SRRE = 1.22; 95% CI: 1.04-1.43). Interestingly, increased by 25% and 33% risk of bladder cancer were observed for red meat and processed meat intake respectively in populations from the American continent. In conclusion, our fi ndings showed that there was an absence of an association between red meat intake and bladder cancer, but suggested that high consumption of processed meat probably correlated with rising risk of bladder cancer. In addition, positive relationships were observed regarding people intake of red and processed meat in the American continent. These findings need to be confirmed in future research.

DNA adduct formation of 2-amino-9H-pyrido[2,3-b]indole and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline in mouse liver and extrahepatic tissues during a subchronic feeding study

Tobacco smoking is a risk factor for cancers of the liver and gastrointestinal (GI) tract, but the causal agents responsible for these cancers are uncertain. 2-Amino-9H-pyrido[2,3-b]indole (AαC) is an abundant heterocyclic aromatic amine present in tobacco smoke. AαC is a liver carcinogen and both a transgene mutagen and inducer of aberrant crypt foci in the colon of mice. We hypothesize that AαC may contribute to DNA damage and tumorigenesis in these organs of smokers. The potential of AαC to induce DNA adduct formation in liver, organs of the GI tract, lung, and urinary bladder, which are target organs of cancer in smokers, was examined using the C57BL/6 mouse as an animal model. AαC (400 or 800 ppm) and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) (300 ppm), a liver and colon carcinogen in C57BL/6 mice, were given in the diet for up to 12 weeks. Liquid chromatography/mass spectrometry was employed to measure DNA adducts. The major DNA adducts of both carcinogens were identified as deoxyguanosine-C8 adducts. The levels of formation of AαC- and MeIQ-DNA adducts were similar in liver and extrahepatic tissues when adjusted for dose. The highest levels of adducts occurred in liver, followed by urinary bladder, and then in cecum and colon; lower DNA adduct levels were formed in the lung and pancreas following 12 weeks of feeding. The high levels of AαC adduct formed in liver, GI tract, and bladder of C57BL/6 mice reinforce the notion that AαC may contribute to DNA damage and cancer of these organs in smokers.