Systematic review: diet-gene interactions and the risk of colorectal cancer

Genetic Variants Associated with Biological Treatment Response in Inflammatory Bowel Disease: A Systematic Review

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the digestive tract usually characterized by diarrhea, rectal bleeding, and abdominal pain. IBD includes Crohn's disease and ulcerative colitis as the main entities. IBD is a debilitating condition that can lead to life-threatening complications, involving possible malignancy and surgery. The available therapies aim to achieve long-term remission and prevent disease progression. Biologics are bioengineered therapeutic drugs that mainly target proteins. Although they have revolutionized the treatment of IBD, their potential therapeutic benefits are limited due to large interindividual variability in clinical response in terms of efficacy and toxicity, resulting in high rates of long-term therapeutic failure. It is therefore important to find biomarkers that provide tailor-made treatment strategies that allow for patient stratification to maximize treatment benefits and minimize adverse events. Pharmacogenetics has the potential to optimize biologics selection in IBD by identifying genetic variants, specifically single nucleotide polymorphisms (SNPs), which are the underlying factors associated with an individual's drug response. This review analyzes the current knowledge of genetic variants associated with biological agent response (infliximab, adalimumab, ustekinumab, and vedolizumab) in IBD. An online literature search in various databases was conducted. After applying the inclusion and exclusion criteria, 28 reports from the 1685 results were employed for the review. The most significant SNPs potentially useful as predictive biomarkers of treatment response are linked to immunity, cytokine production, and immunorecognition.

Plant-based dietary patterns, genetic predisposition and risk of colorectal cancer: a prospective study from the UK Biobank

BACKGROUND

Plant-based dietary patterns may affect colorectal cancer (CRC) related outcomes, while risks differ in the quality of plant foods. We aimed to examine the association of plant-based diet quality with risks of CRC incidence and mortality and whether this association was modified by genetic risk.

METHODS

This prospective cohort study included 186,675 participants free of cancer when the last dietary recall was completed. We calculated three plant-based diet indices (PDIs), i.e., the overall plant-based diet index (PDI), the healthful plant-based diet index (hPDI), and the unhealthful plant-based diet index (uPDI) representing adherence to plant-based diets with diverse quality. Genetic risk was characterized using a weighted polygenic risk score (PRS), capturing overall risk variants associated with CRC. Hazard ratios (HR) and 95% confidential intervals (CI) were estimated by the cause-specific Cox proportional hazards model.

RESULTS

Over a follow-up of 9.5 years, 2163 cases and 466 deaths from CRC were documented. The HR of CRC incidence was 0.88 (95% CI, 0.81-0.96) and 0.91 (95% CI, 0.84-0.99) per 10-score increase in PDI and hPDI, respectively. Compared to the lowest quartile, PDI, hPDI, and uPDI in the highest quartile were associated with a 13% decrease, a 15% decrease, and a 14% increase in risk of incident CRC, respectively. We found a joint association of genetic risk and PDIs with incident CRC, with the highest hazard observed in those carrying higher PRS and adhering to lower-quality PDIs. The inverse association of PDI and hPDI with CRC mortality was pronounced in males.

CONCLUSIONS

Our results suggested that better adherence to overall and healthful plant-based diets was associated with a lower risk of CRC, whereas an unhealthful plant-based diet was associated with a higher CRC risk. Consumption of a higher-quality plant-based diet combined with decreased genetic risk conferred less susceptibility to CRC. Our findings highlighted the importance of food quality when adhering to a plant-based dietary pattern for CRC prevention in the general population.

Obesity-Associated Differentially Methylated Regions in Colon Cancer

Obesity with adiposity is a common disorder in modern days, influenced by environmental factors such as eating and lifestyle habits and affecting the epigenetics of adipose-based gene regulations and metabolic pathways in colorectal cancer (CRC). We compared epigenetic changes of differentially methylated regions (DMR) of genes in colon tissues of 225 colon cancer cases (154 non-obese and 71 obese) and 15 healthy non-obese controls by accessing The Cancer Genome Atlas (TCGA) data. We applied machine-learning-based analytics including generalized regression (GR) as a confirmatory validation model to identify the factors that could contribute to DMRs impacting colon cancer to enhance prediction accuracy. We found that age was a significant predictor in obese cancer patients, both alone (p = 0.003) and interacting with hypomethylated DMRs of ZBTB46, a tumor suppressor gene (p = 0.008). DMRs of three additional genes: HIST1H3I (p = 0.001), an oncogene with a hypomethylated DMR in the promoter region; SRGAP2C (p = 0.006), a tumor suppressor gene with a hypermethylated DMR in the promoter region; and NFATC4 (p = 0.006), an adipocyte differentiating oncogene with a hypermethylated DMR in an intron region, are also significant predictors of cancer in obese patients, independent of age. The genes affected by these DMR could be potential novel biomarkers of colon cancer in obese patients for cancer prevention and progression.

VDR Signaling via the Enzyme NAT2 Inhibits Colorectal Cancer Progression

Recent epidemiological and preclinical evidence indicates that vitamin D₃ inhibits colorectal cancer (CRC) progression, but the mechanism has not been completely elucidated. This study was designed to determine the protective effects of vitamin D₃ and identify crucial targets and regulatory mechanisms in CRC. First, we confirmed that 1,25(OH)₂D₃, the active form of vitamin D₃, suppressed the aggressive phenotype of CRC in vitro and in vivo. Based on a network pharmacological analysis, N-acetyltransferase 2 (NAT2) was identified as a potential target of vitamin D₃ against CRC. Clinical data of CRC patients from our hospital and bioinformatics analysis by online databases indicated that NAT2 was downregulated in CRC specimens and that the lower expression of NAT2 was correlated with a higher metastasis risk and lower survival rate of CRC patients. Furthermore, we found that NAT2 suppressed the proliferation and migration capacity of CRC cells, and the JAK1/STAT3 signaling pathway might be the underlying mechanism. Moreover, Western blot and immunofluorescence staining assays demonstrated that 1,25(OH)₂D₃ promoted NAT2 expression, and the chromatin immunoprecipitation assay indicated that the vitamin D receptor (VDR) transcriptionally regulated NAT2. These findings expand the potential uses of vitamin D₃ against CRC and introduce VDR signaling via the enzyme NAT2 as a potential diagnostic and therapeutic target for CRC.

Cancer health disparities in racial/ethnic minorities in the United States

There are well-established disparities in cancer incidence and outcomes by race/ethnicity that result from the interplay between structural, socioeconomic, socio-environmental, behavioural and biological factors. However, large research studies designed to investigate factors contributing to cancer aetiology and progression have mainly focused on populations of European origin. The limitations in clinicopathological and genetic data, as well as the reduced availability of biospecimens from diverse populations, contribute to the knowledge gap and have the potential to widen cancer health disparities. In this review, we summarise reported disparities and associated factors in the United States of America (USA) for the most common cancers (breast, prostate, lung and colon), and for a subset of other cancers that highlight the complexity of disparities (gastric, liver, pancreas and leukaemia). We focus on populations commonly identified and referred to as racial/ethnic minorities in the USA-African Americans/Blacks, American Indians and Alaska Natives, Asians, Native Hawaiians/other Pacific Islanders and Hispanics/Latinos. We conclude that even though substantial progress has been made in understanding the factors underlying cancer health disparities, marked inequities persist. Additional efforts are needed to include participants from diverse populations in the research of cancer aetiology, biology and treatment. Furthermore, to eliminate cancer health disparities, it will be necessary to facilitate access to, and utilisation of, health services to all individuals, and to address structural inequities, including racism, that disproportionally affect racial/ethnic minorities in the USA.

Gene-environment interactions and colorectal cancer risk: An umbrella review of systematic reviews and meta-analyses of observational studies

The cause of colorectal cancer (CRC) is multifactorial, involving both genetic variants and environmental risk factors. We systematically searched the MEDLINE, EMBASE, China National Knowledge Infrastructure (CNKI) and Wanfang databases from inception to December 2016, to identify systematic reviews and meta-analyses of observational studies that investigated gene-environment (G×E) interactions in CRC risk. Then, we critically evaluated the cumulative evidence for the G×E interactions using an extension of the Human Genome Epidemiology Network's Venice criteria. Overall, 15 articles reporting systematic reviews of observational studies on 89 G×E interactions, 20 articles reporting meta-analyses of candidate gene- or single-nucleotide polymorphism-based studies on 521 G×E interactions, and 8 articles reporting 33 genome-wide G×E interaction analyses were identified. On the basis of prior and observed scores, only the interaction between rs6983267 (8q24) and aspirin use was found to have a moderate overall credibility score as well as main genetic and environmental effects. Though 5 other interactions were also found to have moderate evidence, these interaction effects were tenuous due to the lack of main genetic effects and/or environmental effects. We did not find highly convincing evidence for any interactions, but several associations were found to have moderate strength of evidence. Our conclusions are based on application of the Venice criteria which were designed to provide a conservative assessment of G×E interactions and thus do not include an evaluation of biological plausibility of an observed joint effect.

Intake of Red and Processed Meat, Use of Non-Steroid Anti-Inflammatory Drugs, Genetic Variants and Risk of Colorectal Cancer: A Prospective Study of the Danish "Diet, Cancer and Health" Cohort

Red and processed meat have been associated with increased risk of colorectal cancer (CRC), whereas long-term use of non-steroid anti-inflammatory drugs (NSAIDs) may reduce the risk. The aim was to investigate potential interactions between meat intake, NSAID use, and gene variants in fatty acid metabolism and NSAID pathways in relation to the risk of CRC. A nested case-cohort study of 1038 CRC cases and 1857 randomly selected participants from the Danish prospective “Diet, Cancer and Health” study encompassing 57,053 persons was performed using the Cox proportional hazard model. Gene variants in SLC25A20, PRKAB1, LPCAT1, PLA2G4A, ALOX5, PTGER3, TP53, CCAT2, TCF7L2, and BCL2 were investigated. CCAT2 rs6983267 was associated with the risk of CRC per se (p < 0.01). Statistically significant interactions were found between intake of red and processed meat and CCAT2 rs6983267, TP53 rs1042522, LPCAT1 rs7737692, SLC25A20 rs7623023 (p_interaction = 0.04, 0.04, 0.02, 0.03, respectively), and the use of NSAID and alcohol intake and TP53 rs1042522 (p_interaction = 0.04, 0.04, respectively) in relation to the risk of CRC. No other consistent associations or interactions were found. This study replicated an association of CCAT2 rs6983267 with CRC and an interaction between TP53 rs1042522 and NSAID in relation to CRC. Interactions between genetic variants in fatty acid metabolism and NSAID pathways and the intake of red and processed meat were found. Our results suggest that meat intake and NSAID use affect the same carcinogenic mechanisms. All new findings should be sought replicated in independent prospective studies. Future studies on the cancer-protective effects of aspirin/NSAID should include gene and meat assessments.

Meat and fiber intake and interaction with pattern recognition receptors (TLR1, TLR2, TLR4, and TLR10) in relation to colorectal cancer in a Danish prospective, case-cohort study

Background

Meat and dietary fiber are associated with increased and decreased risk of colorectal cancer (CRC), respectively. Toll-like receptors (TLRs) regulate the intestinal immune response in a complex interplay between the mucosal epithelium and the microbiota and may therefore be important modulators of diet-induced CRC together with other inflammatory mediators.

Objective

Our aim was to investigate the association between functional TLR polymorphisms and risk of CRC and the interaction with dietary factors. Additionally, interactions with previously studied polymorphisms in IL10, IL1B, PTGS2, and NFKB1 were assessed in order to examine possible biological pathways in meat-induced CRC.

Design

A nested case-cohort study of 897 CRC cases and 1689 randomly selected participants from the Danish prospective "Diet, Cancer and Health" study encompassing 57,053 persons was performed using Cox proportional hazard models and the likelihood ratio test.

Results

We found associations between polymorphisms in TLR2 (P = 0.018) and TLR4 (P = 0.044) and risk of CRC per se, interactions between intake of red and processed meat (10 g/d) and polymorphisms in TLR1 (P-interaction = 0.032) and TLR10 (P-interaction = 0.026 and 0.036), and intake of cereals (50 g/d) and TLR4 (P-interaction = 0.044) in relation to risk of CRC. Intake of red and processed meat also interacted with combinations of polymorphisms in TLR1 and TLR10 and polymorphisms in NFKB1, IL10, IL1B, and PTGS2 (P-interaction; TLR1/rs4833095 × PTGS2/rs20417 = 0.021, TLR10/rs11096955 × IL10/rs3024505 = 0.047, TLR10/rs11096955 × PTGS2/rs20417 = 0.017, TLR10/rs4129009 × NFKB1/rs28362491 = 0.027, TLR10/rs4129009 × IL1B/rs4848306 = 0.020, TLR10/rs4129009 × IL1B/rs1143623 = 0.021, TLR10/rs4129009 × PTGS2/rs20417 = 0.027), whereas intake of dietary fiber (10 g/d) interacted with combinations of polymorphisms in TLR4, IL10, and PTGS2 (P-interaction; TLR4/rs1554973 × IL10/rs3024505 = 0.0012, TLR4/rs1554973 × PTGS2/rs20417 = 0.0041, TLR4/rs1554973 × PTGS2/rs5275 = 0.0064).

Conclusions

Our study suggests that meat intake may activate TLRs at the epithelial surface, leading to CRC via inflammation by nuclear transcription factor-κB-initiated transcription of inflammatory genes, whereas intake of fiber may protect against CRC via TLR4-mediated secretion of interleukin-10 and cyclooxygenase-2. Our results should be replicated in other prospective cohorts with well-characterized participants. The trial was registered at www.clinicaltrials.gov as NCT03250637.

Dietary components that counteract the increased risk of colorectal cancer related to red meat consumption

Western-style diets are associated with an increased risk of colorectal cancer (CRC). In particular, a strong correlation has been documented between CRC and the consumption of large amounts of red meat, especially processed red meat. Compared with white meat, red meat contains high levels of haem iron, a molecule that can exert a variety of genotoxic and other adverse effects on the colonic epithelium. According to current international guidelines, the reduction of red meat intake combined with the consumption of food containing antioxidant and chemoprotective substances may significantly reduce the risk of developing CRC. The dietary strategies that can help to contrast the harmful effects of haem iron are reported and discussed in this review.

Genetic Factors Interact With Tobacco Smoke to Modify Risk for Inflammatory Bowel Disease in Humans and Mice

BACKGROUND & AIMS

The role of tobacco smoke in the etiology of inflammatory bowel disease (IBD) is unclear. We investigated interactions between genes and smoking (gene-smoking interactions) that affect risk for Crohn's disease (CD) and ulcerative colitis (UC) in a case-only study of patients and in mouse models of IBD.

METHODS

We used 55 Immunochip-wide datasets that included 19,735 IBD cases (10,856 CD cases and 8879 UC cases) of known smoking status. We performed 3 meta-analyses each for CD, UC, and IBD (CD and UC combined), comparing data for never vs ever smokers, never vs current smokers, and never vs former smokers. We studied the effects of exposure to cigarette smoke in Il10^-/- and Nod2^-/- mice, as well as in Balb/c mice without disruption of these genes (wild-type mice). Mice were exposed to the smoke of 5 cigarettes per day, 5 days a week, for 8 weeks, in a ventilated smoking chamber, or ambient air (controls). Intestines were collected and analyzed histologically and by reverse transcription polymerase chain reaction.

RESULTS

We identified 64 single nucleotide polymorphisms (SNPs) for which the association between the SNP and IBD were modified by smoking behavior (meta-analysis Wald test P < 5.0 × 10^-5; heterogeneity Cochrane Q test P > .05). Twenty of these variants were located within the HLA region at 6p21. Analysis of classical HLA alleles (imputed from SNP genotypes) revealed an interaction with smoking. We replicated the interaction of a variant in NOD2 with current smoking in relation to the risk for CD (frameshift variant fs1007insC; rs5743293). We identified 2 variants in the same genomic region (rs2270368 and rs17221417) that interact with smoking in relation to CD risk. Approximately 45% of the SNPs that interact with smoking were in close vicinity (≤1 Mb) to SNPs previously associated with IBD; many were located near or within genes that regulate mucosal barrier function and immune tolerance. Smoking modified the disease risk of some variants in opposite directions for CD vs UC. Exposure of Interleukin 10 (il10)-deficient mice to cigarette smoke accelerated development of colitis and increased expression of interferon gamma in the small intestine compared to wild-type mice exposed to smoke. NOD2-deficient mice exposed to cigarette smoke developed ileitis, characterized by increased expression of interferon gamma, compared to wild-type mice exposed to smoke.

CONCLUSIONS

In an analysis of 55 Immunochip-wide datasets, we identified 64 SNPs whose association with risk for IBD is modified by tobacco smoking. Gene-smoking interactions were confirmed in mice with disruption of Il10 and Nod2-variants of these genes have been associated with risk for IBD. Our findings from mice and humans revealed that the effects of smoking on risk for IBD depend on genetic variants.

N-acetyl transferase 2/environmental factors and their association as a modulating risk factor for sporadic colon and rectal cancer

OBJECTIVES

The aim of this study was to evaluate the association between environmental factors and colon or rectal cancer after adjusting for N-acetyl transferase 2 (NAT2) phenotypes.

METHODS

Ninety-six patients with sporadic colon cancer, 54 with sporadic rectal cancer and 162 control subjects were genotyped for NAT2-T341C, G590A, G857A, A845C, and C481T using sequencing and PCR-RFLP analysis.

RESULTS

The risk for colon cancer was increased in carriers of the homozygous negative genotypes for NAT2*5C-T341C, NAT2*6B-G590A, NAT2*7B-G857A, NAT2*18-A845C, and NAT2*5A-C481T. The risk for rectal cancer was increased in carriers of the homozygous negative genotypes for NAT2*5C-T341C, NAT2*7B-G857A, and NAT2*5A-C481T. High fried red meat intake associated with NAT2-T341C, G590A, G857A, A845C, and C481T rapid acetylator allele determines a risk of 2.39 (P=.002), 2.39 (P=.002), 2.37 (P=.002), 2.28 (P=.004), and 2.51 (P=.001), respectively, for colon cancer, whereas in the case of rectal cancer, the risk increased to 7.55 (P<.001), 7.7 (P<.001), 7.83 (P<.001), 7.51 (P<.001), and 8.62 (P<.001), respectively. Alcohol consumption associated with the NAT2 -T341C, G590A, G857A, A845C, and C481T rapid acetylator allele induces a risk of 10.63 (P<.001), 12.04 (P<.001), 9.76 (P<.001), 10.25 (P<.001), and 9.54 (P<.001), respectively, for colon cancer, whereas the risk for rectal cancer is 9.72 (P<.001), 11.24 (P<.001), 13.07 (P<.001), 10.04 (P<.001), and 9.43 (P<.001), respectively. Smokers with NAT2-T341C, G590A, G857A, A845C, and C481T rapid acetylator allele have a risk of 4.87, 4.25, 4.18, 3.81, and 3.82, respectively, to develop colon cancer.

CONCLUSIONS

Fried red meat, alcohol, and smoking increase the risk of sporadic CRC, especially of colon cancer, in the case of rapid acetylators for the NAT2 variants.

Systematic review: genetic biomarkers associated with anti-TNF treatment response in inflammatory bowel diseases

BACKGROUND

Personalised medicine, including biomarkers for treatment selection, may provide new algorithms for more effective treatment of patients. Genetic variation may impact drug response and genetic markers could help selecting the best treatment strategy for the individual patient.

AIM

To identify polymorphisms and candidate genes from the literature that are associated with anti-tumour necrosis factor (TNF) treatment response in patients with inflammatory bowel diseases (IBD), Crohn's disease (CD) and ulcerative colitis.

METHODS

We performed a PubMed literature search and retrieved studies reporting original data on association between polymorphisms and anti-TNF treatment response and conducted a meta-analysis.

RESULTS

A functional polymorphism in FCGR3A was significantly associated with anti-TNF treatment response among CD patients using biological response criterion (decrease in C-reactive protein, levels). Meta-analyses showed that polymorphisms in TLR2 (rs3804099, OR (95% CI) = 2.17 (1.35-3.47)], rs11938228 [OR = 0.64 (0.43-0.96)], TLR4 (rs5030728) [OR = 3.18 (1.63-6.21)], TLR9 (rs352139) [OR = 0.43 (0.21-0.88)], TNFRSF1A (rs4149570) [OR = 2.06 (1.02-4.17)], IFNG (rs2430561) [OR = 1.66 (1.05-2.63)], IL6 (rs10499563) [OR = 1.65 (1.04-2.63)] and IL1B (rs4848306) [OR = 1.88 (1.05-3.35)] were significantly associated with response among IBD patients using clinical response criteria. A positive predictive value of 0.96 was achieved by combining five genetic markers in an explorative analysis.

CONCLUSIONS

There are no genetic markers currently available which are adequately predictive of anti-TNF response for use in the clinic. Genetic markers bear the advantage that they do not change over time. Therefore, hypothesis-free approaches, testing a large number of polymorphisms in large, well-characterised cohorts, are required in order to identify genetic profiles with larger effect sizes, which could be employed as biomarkers for treatment selection in clinical settings.

Polymorphisms in ATP-binding cassette transporter genes and interaction with diet and life style factors in relation to colorectal cancer in a Danish prospective case-cohort study

BACKGROUND AND AIMS

The ATP-binding cassette (ABC) transporter family transports various molecules across the enterocytes in the gut protecting the intestine against potentially harmful substances. Moreover, ABC transporters are involved in mucosal immune defence through interaction with cytokines. The study aimed to assess whether polymorphisms in ABCB1, ABCC2 and ABCG2 were associated with risk of colorectal cancer (CRC) and to investigate gene-environment (dietary factors, smoking and use of non-steroidal anti-inflammatory drugs) and gene-gene interactions between previously studied polymorphisms in IL1B and IL10 and ABC transporter genes in relation to CRC risk.

MATERIALS AND METHODS

We used a Danish prospective case-cohort study of 1010 CRC cases and 1829 randomly selected participants from the Danish Diet, Cancer and Health cohort. Incidence rate ratios were calculated based on Cox' proportional hazards model.

RESULTS

None of the polymorphisms were associated with CRC, but ABCB1 and ABCG2 haplotypes were associated with risk of CRC. ABCB1/rs1045642 interacted with intake of cereals and fiber (p-Value for interaction (P(int)) = 0.001 and 0.01, respectively). In a three-way analysis, both ABCB1/rs1045642 and ABCG2/rs2231137 in combination with IL10/rs3024505 interacted with fiber intake in relation to risk of CRC (P(int) = 0.0007 and 0.009).

CONCLUSIONS

Our results suggest that the ABC transporters P-glycoprotein/multidrug resistance 1 and BRCP, in cooperation with IL-10, are involved in the biological mechanism underlying the protective effect of fiber intake in relation to CRC. These results should be replicated in other cohorts to rule out chance findings.

Novel understanding of ABC transporters ABCB1/MDR/P-glycoprotein, ABCC2/MRP2, and ABCG2/BCRP in colorectal pathophysiology

AIM: To evaluate ATP-binding cassette (ABC) transporters in colonic pathophysiology as they had recently been related to colorectal cancer (CRC) development.

METHODS: Literature search was conducted on PubMed using combinations of the following terms: ABC transporters, ATP binding cassette transporter proteins, inflammatory bowel disease, ulcerative, colitis, Crohns disease, colorectal cancer, colitis, intestinal inflammation, intestinal carcinogenesis, ABCB1/P-glycoprotein (P-gp/CD243/MDR1), ABCC2/multidrug resistance protein 2 (MRP2) and ABCG2/breast cancer resistance protein (BCRP), Abcb1/Mdr1a, abcc2/Mrp2, abcg2/Bcrp, knock-out mice, tight junction, membrane lipid function.

RESULTS: Recently, human studies reported that changes in the levels of ABC transporters were early events in the adenoma-carcinoma sequence leading to CRC. A link between ABCB1, high fat diet and gut microbes in relation to colitis was suggested by the animal studies. The finding that colitis was preceded by altered gut bacterial composition suggests that deletion of Abcb1 leads to fundamental changes of host-microbiota interaction. Also, high fat diet increases the frequency and severity of colitis in specific pathogen-free Abcb1 KO mice. The Abcb1 KO mice might thus serve as a model in which diet/environmental factors and microbes may be controlled and investigated in relation to intestinal inflammation. Potential molecular mechanisms include defective transport of inflammatory mediators and/or phospholipid translocation from one side to the other of the cell membrane lipid bilayer by ABC transporters affecting inflammatory response and/or function of tight junctions, phagocytosis and vesicle trafficking. Also, diet and microbes give rise to molecules which are potential substrates for the ABC transporters and which may additionally affect ABC transporter function through nuclear receptors and transcriptional regulation. Another critical role of ABCB1 was suggested by the finding that ABCB1 expression identifies a subpopulation of pro-inflammatory Th17 cells which were resistant to treatment with glucocorticoids. The evidence for the involvement of ABCC2 and ABCG2 in colonic pathophysiology was weak.

CONCLUSION: ABCB1, diet, and gut microbes mutually interact in colonic inflammation, a well-known risk factor for CRC. Further insight may be translated into preventive and treatment strategies.

Polymorphisms in NFKB1 and TLR4 and interaction with dietary and life style factors in relation to colorectal cancer in a Danish prospective case-cohort study

Maintenance of a balance between commensal bacteria and the mucosal immune system is crucial and intestinal dysbiosis may be a key event in the pathogenesis of colorectal cancer (CRC). The toll-like receptor 4 (TLR4) is an important pattern-recognition receptor that regulates inflammation and barrier function in the gut by a mechanism that involves activation of the nuclear factor-κB (NF-κB) transcription factor. Dietary and life style factors may impact these functions. We therefore used a Danish prospective case-cohort study of 1010 CRC cases and 1829 randomly selected participants from the Danish Diet, Cancer and Health cohort to investigate three polymorphisms in NFKB1 and TLR4 and their possible interactions with diet and life style factors in relation to risk of CRC. Homozygous carriage of the variant allele of the TLR4/rs5030728 polymorphism was associated with increased risk of CRC (incidence rate ratio (IRR) = 1.30; 95% confidence interval (CI): 1.05-1.60; P = 0.02 (gene-dose model); IRR = 1.24; 95%CI: 1.01-1.51; P = 0.04 (recessive model)). Del-carriers of the NFKB1/rs28362491 polymorphism had a 17% (95%CI: 1.03-1.34; P = 0.02) increased risk of CRC compared to homozygous carriers of the ins-allele. However, none of these risk estimates withstood adjustment for multiple comparisons. We found no strong gene-environment interactions between the examined polymorphism and diet and life style factors in relation to CRC risk.

No association between HMOX1 and risk of colorectal cancer and no interaction with diet and lifestyle factors in a prospective Danish case-cohort study

Red meat is a risk factor for colorectal cancer (CRC). We wanted to evaluate whether a functional polymorphism in the HMOX1 gene encoding heme oxygenase modifies risk of CRC or interacts with diet or lifestyle factors because this would identify heme or heme iron as a risk factor of CRC. The HMOX1 A-413T (rs2071746) was assessed in relation to risk of colorectal cancer (CRC) and interactions with diet (red meat, fish, fiber, cereals, fruit and vegetables) and lifestyle (use of non-steroidal anti-inflammatory drug and smoking status) were assessed in a case-cohort study of 928 CRC cases and a comparison group of 1726 randomly selected participants from a prospective study of 57,053 persons. No association between HMOX1 A-413T and CRC risk was found (TT vs. AA + TA; IRR = 1.15, 95% CI: 0.98-1.36, p = 0.10 for the adjusted estimate). No interactions were found between diet or lifestyle and HMOX1 A-413T. HMOX1 A-413T was not associated with CRC risk and no interactions with diet or lifestyle were identified in this large, prospective cohort with high meat intake. The results reproduced the previous findings from the same cohort and did not support a link between heme or heme iron and colorectal cancer. These results should be sought and replicated in other well-characterized cohorts with high meat intake.

Interactions between meat intake and genetic variation in relation to colorectal cancer

Meat intake is associated with the risk of colorectal cancer. The objective of this systematic review was to evaluate interactions between meat intake and genetic variation in order to identify biological pathways involved in meat carcinogenesis. We performed a literature search of PubMed and Embase using “interaction”, “meat”, “polymorphisms”, and “colorectal cancer”, and data on meat–gene interactions were extracted. The studies were divided according to whether information on meat intake was collected prospectively or retrospectively. In prospective studies, interactions between meat intake and polymorphisms in PTGS2 (encoding COX-2), ABCB1, IL10, NFKB1, MSH3, XPC (P_int = 0.006, 0.01, 0.04, 0.03, 0.002, 0.01, respectively), but not IL1B, HMOX1, ABCC2, ABCG2, NR1I2 (encoding PXR), NR1H2 (encoding LXR), NAT1, NAT2, MSH6, or MLH1 in relation to CRC were found. Interaction between a polymorphism in XPC and meat was found in one prospective and one case–control study; however, the directions of the risk estimates were opposite. Thus, none of the findings were replicated. The results from this systematic review suggest that genetic variation in the inflammatory response and DNA repair pathway is involved in meat-related colorectal carcinogenesis, whereas no support for the involvement of heme and iron from meat or cooking mutagens was found. Further studies assessing interactions between meat intake and genetic variation in relation to CRC in large well-characterised prospective cohorts with relevant meat exposure are warranted.

Colorectal cancer susceptibility: apparent gender-related modulation by ABCB1 gene polymorphisms

BACKGROUND

The ATP-binding cassette transporter B1 (ABCB1) gene codes for a membrane efflux pump localized in epithelial cells. Together with other Permeability-glycoproteins in the small and large intestine, its product represents a barrier against xenobiotics, bacterial toxins, drugs and other substances introduced with diet, including carcinogens. The aim of this investigation was to verify the possible contribution of ABCB1 single nucleotide polymorphisms (SNPs) to the genetic risk of colorectal cancer (CRC).

RESULTS

DNA obtained from the peripheral blood of 98 CRC patients and 100 healthy controls was genotyped for the three selected SNPs: 1236C > T (rs1128503), 2677G > T/A (rs2032582), and 3435C > T (rs1045642). Molecular data were analyzed to asses allele and haplotype association with CRC. No evidence of an association between ABCB1 alleles and CRC occurrence as a whole was found. However, ABCB1 showed either association with carcinoma of the sigmoid colon, and appeared able to influence the sex ratio among CRC patients. These two effects seemed to act independently based on multivariate analysis. We showed that ABCB1 polymorphisms were able to influence CRC susceptibility related to tumor localization and patient gender.

CONCLUSIONS

We suggest that sensitivity to undetermined risk factors could depend on the genetic background of ABCB1 locus, with a mechanism that also depends on patient gender.

Intestinal PTGS2 mRNA levels, PTGS2 gene polymorphisms, and colorectal carcinogenesis

Background & Aims

Inflammation is a major risk factor for development of colorectal cancer (CRC). Prostaglandin synthase cyclooxygenase-2 (COX-2) encoded by the PTGS2 gene is the rate limiting enzyme in prostaglandin synthesis and therefore plays a distinct role as regulator of inflammation.

Methods

PTGS2 mRNA levels were determined in intestinal tissues from 85 intestinal adenoma cases, 115 CRC cases, and 17 healthy controls. The functional PTGS2 polymorphisms A-1195G (rs689466), G-765C (rs20417), T8473C (rs5275) were assessed in 200 CRC cases, 991 adenoma cases and 399 controls from the Norwegian KAM cohort.

Results

PTGS2 mRNA levels were higher in mild/moderate adenoma tissue compared to morphologically normal tissue from the same individual (P<0.0001) and (P<0.035) and compared to mucosa from healthy individuals (P<0.0039) and (P<0.0027), respectively. In CRC patients, PTGS2 mRNA levels were 8–9 times higher both in morphologically normal tissue and in cancer tissue, compared to healthy individuals (P<0.0001). PTGS2 A-1195G variant allele carriers were at reduced risk of CRC (odds ratio (OR) = 0.52, 95% confidence interval (95% CI): 0.28–0.99, P = 0.047). Homozygous carriers of the haplotype encompassing the A-1195G and G-765C wild type alleles and the T8473C variant allele (PTGS2 AGC) were at increased risk of CRC as compared to homozygous carriers of the PTGS2 AGT (A-1195G, G-765C, T8473C) haplotype (OR = 5.37, 95% CI: 1.40–20.5, P = 0.014). No association between the investigated polymorphisms and PTGS2 mRNA levels could be detected.

Conclusion

High intestinal PTGS2 mRNA level is an early event in colorectal cancer development as it occurs already in mild/moderate dysplasia. PTGS2 polymorphisms that have been associated with altered PTGS2 mRNA levels/COX-2 activity in some studies, although not the present study, were associated with colorectal cancer risk. Thus, both PTGS2 polymorphisms and PTGS2 mRNA levels may provide information regarding CRC risk.

Systematic review: interactions between aspirin, and other nonsteroidal anti-inflammatory drugs, and polymorphisms in relation to colorectal cancer

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) include aspirin (acetylsalicylic acid, ASA). Long-term use of NSAIDs has been associated with lowered risk of colorectal cancer (CRC), but the use is hampered by adverse effects. Also, the anti-carcinogenic effects of NSAIDs are incompletely understood. Understanding biological effects of NSAIDs may help developing new preventive medical strategies.

AIM

To identify gene-environment interactions between genetic variation and NSAID use in relation to risk of CRC.

METHODS

We performed a PubMed literature search and all studies reporting original data on interactions between NSAIDs and polymorphisms in relation to CRC were evaluated.

RESULTS

We found indications that aspirin interacted with rs6983267 close to MYC (encoding a transcription factor involved in cell cycle progression, apoptosis and cellular transformation) and NSAIDs interacted with rs3024505 and rs1800872 in or close to IL10 (encoding IL-10) in preventing CRC. Homozygous carriers of the variant allele of rs6983267 (ca. 25% of the population) halved their risk for CRC by aspirin use compared to homozygous wildtype carriers who did not benefit from aspirin intake. No interaction between use of NSAIDs and PTGS-2 (encoding COX-2) in relation to CRC risk was detected. Other findings of interactions between genes in inflammatory and oncogenic pathways and NSAIDs were considered suggestive.

CONCLUSIONS

Knowledge of underlying biological effects of NSAIDs in relation to CRC is scarce and the basis for stratifying the patients for preventive treatment is not yet available. Further studies assessing interactions between long-term NSAID exposure and genetic variation in relation to CRC are warranted in large well-characterised prospective cohorts.

GST gene polymorphisms and the risk of colorectal cancer development

Increasingly often, molecular studies of colorectal cancer focus on low penetrance genes. Among the factors potentially modifying the risk of contracting colorectal cancer is the glutathione S-transferase (GST) gene family, encoding enzymes of the glutathione transferase type. Proteins of the GST family (glutathione S-transferases) are enzymes detoxifying a wide range of hazardous substances, such as reactive oxygen species (ROS) or xenobionts. Thus, their role, among other things, is the protection of DNA against oxidative damage, which may lead to mutations, and in consequence, favour carcinogenesis. GST gene polymorphisms may affect the functioning of the encoded enzymes, exerting an effect on the level of DNA damage, and therefore may have an indirect influence on the risk of the development of cancer. At present, there are many studies available concerning GST gene polymorphisms as factors modulating the risk of developing cancer, including colorectal cancer.

Relationship between tumor and peripheral blood NPRL2 mRNA levels in patients with colorectal adenoma and colorectal cancer

NPRL2 is a tumor suppressor gene involved in the progression of human cancer. The present study investigated whether NPRL2 expression correlates with colorectal cancer (CRC) progression. Colorectal tissue and peripheral blood samples were obtained from 62 patients with CRC, 38 patients with colorectal adenomas and 51 normal controls. NPRL2 mRNA levels in tissue samples and blood were measured using quantitative real-time PCR. NPRL2 protein expression was determined by immunohistochemistry. NPRL2 protein expression in CRCs was significantly lower than in the adenomas or normal colorectal tissue. NPRL2 mRNA expression was significantly decreased in adenomas compared with normal controls (P<0.0001) and it was further decreased in colorectal tumors compared with adenomas (P<0.0001). NPRL2 mRNA levels expression correlated with tumor stage. In addition, NPRL2 mRNA levels in the blood correlated with the levels detected in tumors. Furthermore, receiver operating characteristic (ROC) analysis showed that NPRL2 expression in blood could distinguish colorectal adenomas and CRCs from normal controls. NPRL2 mRNA expression in CRC tumor tissues and peripheral blood correlated with colorectal tumor progression. Based on our findings, we can conclude that NPRL2 mRNA blood levels could be a potentially useful marker for the detection of early stage adenomas and CRCs.

Interactions between diet, lifestyle and IL10, IL1B, and PTGS2/COX-2 gene polymorphisms in relation to risk of colorectal cancer in a prospective Danish case-cohort study

Background & Aims

Diet contributes to colorectal cancer development and may be potentially modified. We wanted to identify the biological mechanisms underlying colorectal carcinogenesis by assessment of diet-gene interactions.

Methods

The polymorphisms IL10 C-592A (rs1800872), C-rs3024505-T, IL1b C-3737T (rs4848306), G-1464C (rs1143623), T-31C (rs1143627) and PTGS2 (encoding COX-2) A-1195G (rs689466), G-765C (rs20417), and T8473C (rs5275) were assessed in relation to risk of colorectal cancer (CRC) and interaction with diet (red meat, fish, fibre, cereals, fruit and vegetables) and lifestyle (non-steroid-anti-inflammatory drug use and smoking status) was assessed in a nested case-cohort study of nine hundred and seventy CRC cases and 1789 randomly selected participants from a prospective study of 57,053 persons.

Results

IL1b C-3737T, G-1464C and PTGS2 T8473C variant genotypes were associated with risk of CRC compared to the homozygous wildtype genotype (IRR=0.81, 95%CI: 0.68-0.97, p=0.02, and IRR=1.22, 95%CI: 1.04-1.44, p=0.02, IRR=0.75, 95%CI: 0.57-0.99, p=0.04, respectively). Interactions were found between diet and IL10 rs3024505 (P-value for interaction (P_int); meat=0.04, fish=0.007, fibre=0.0008, vegetables=0.0005), C-592A (P_int; fibre=0.025), IL1b C-3737T (P_int; vegetables=0.030, NSAID use=0.040) and PTGS2 genotypes G-765C (P_int; meat=0.006, fibre=0.0003, fruit 0.004), and T8473C (P_int; meat 0.049, fruit=0.03) and A-1195G (P_int; meat 0.038, fibre 0.040, fruit=0.059, vegetables=0.025, and current smoking=0.046).

Conclusions

Genetically determined low COX-2 and high IL-1β activity were associated with increased risk of CRC in this northern Caucasian cohort. Furthermore, interactions were found between IL10, IL1b, and PTGS2 and diet and lifestyle factors in relation to CRC. The present study demonstrates that gene-environment interactions may identify genes and environmental factors involved in colorectal carcinogenesis.

Meta-analysis of the association between NQO1 Pro187Ser polymorphism and colorectal cancer in Asians

There were a number of studies performed to assess the association between NQO1 Pro187Ser polymorphism and colorectal cancer risk in Asians, but no consensus was available up to now. We conducted a meta-analysis to assess the association between NQO1 Pro187Ser polymorphism and colorectal cancer risk in Asians. Case-control studies investigating the association between NQO1 Pro187Ser polymorphism and colorectal cancer risk in Asians were searched in Pubmed and Wanfang databases. Pooled odds ratio (OR) and 95% confidence interval (95% CI) was calculated. Finally, seven studies involving a total of 2,051 cases and 2,798 controls met the inclusion criteria and were included into the meta-analysis. Overall, there was an obvious association between NQO1 Pro187Ser polymorphism and colorectal cancer risk in Asians (Ser versus Pro: OR = 1.42, 95% CI 1.08-1.87, P = 0.013; SerSer versus ProPro: OR = 1.86, 95% CI 1.08-3.19, P = 0.024; SerSer/ProSer versus ProPro: OR = 1.61, 95% CI 1.10-2.35, P = 0.014; SerSer versus ProPro/ProSer: OR = 1.46, 95% CI 1.02-2.10, P = 0.041). There was low risk of publication bias in the meta-analysis. This meta-analysis suggests that there is an obvious association between NQO1 Pro187Ser polymorphism and colorectal cancer risk in Asians.

Low ABCB1 gene expression is an early event in colorectal carcinogenesis

The ABCB1/MDR1 gene product ABCB1/P-glycoprotein is implicated in the development of colorectal cancer (CRC). NFKB1 encodes transcription factors regulating expression of a number of genes including ABCB1. We have previously found association between the ABCB1 C-rs3789243-T polymorphism and CRC risk and interactions between the ABCB1 C-rs3789243-T and C3435T polymorphisms and meat intake in relation to CRC risk (Andersen, BMC Cancer, 2009, 9, 407). ABCB1 and NFKB1 mRNA levels were assessed in intestinal tissue from 122 CRC cases, 101 adenoma cases (12 with severe dysplasia, 89 with mild-moderate dysplasia) and from 18 healthy individuals, together with gene polymorphisms in ABCB1 and NFKB1. ABCB1 mRNA levels were highest in the healthy individuals and significantly lower in mild/moderate and severe dysplasia tissue (P<0.05 for both), morphologically normal tissues close to the tumour (P<0.05), morphologically normal tissue at a distance from the tumour (P<0.05) and CRC tissue (P<0.001). Furthermore, ABCB1 mRNA levels were lower in adenomas and carcinomas compared to morphologically normal tissue from the same individuals (P<0.01). The ABCB1 C-rs3789243-T and NFKB1 -94ins/del homozygous variant genotypes were associated with low ABCB1 mRNA levels in morphologically normal sigmoid tissue from adenoma cases (P<0.05 for both). NFKB1 mRNA levels were lower in both tumour and normal tissue from cancer patients (P<0.001) as compared to healthy individuals but we were unable to show association between NFKB1 -94ins/del genotype and NFKB1 mRNA levels. This study suggests that low ABCB1 mRNA levels are an early event in CRC development and that the two polymorphisms affect ABCB1 mRNA levels whereas low NFKB1 mRNA levels occur later in carcinogenesis. Low ABCB1 protein levels may promote colorectal carcinogenesis through increasing intracellular exposure to carcinogenic ABCB1 substrates.

Associations of CYP2E1 rs2031920 and rs3813867 polymorphisms with colorectal cancer risk: a systemic review and meta-analysis

Cytochrome P450 2E1 (CYP2E1) is a natural enzyme involved in the metabolic activation of many carcinogens, and the functional polymorphisms in the CYP2E1 gene might have impacts on colorectal cancer risk. Many studies were published to assess the associations of CYP2E1 rs2031920 and rs3813867 polymorphisms with colorectal cancer risk, but no consistent findings were reported. A systemic review and meta-analysis of eligible studies was performed to comprehensively assess the associations above. Odds ratios (ORs) with 95 % confidence interval (95 % CIs) were used to assess the strength of the associations. Seventeen studies from 15 publications with 17,082 individuals were finally included into this meta-analysis. Meta-analysis of the 13 studies on CYP2E1 rs2031920 polymorphism showed that there was a significant association between CYP2E1 rs2031920 polymorphism and colorectal cancer risk under two genetic models (c2 versus c1: OR = 1.19, 95 % CI 1.03-1.37, P = 0.022; c2c2/c2c1 versus c1c1: OR = 1.16, 95 % CI 1.00-1.35, P = 0.046). Meta-analysis of those four case-control studies on CYP2E1 rs3813867 polymorphism showed that there was no significant association between CYP2E1 rs3813867 polymorphism and colorectal cancer risk under all contrast models (c2 versus c1: OR = 0.96, 95 % CI 0.80-1.16, P = 0.672; c2c2 versus c1c1: OR = 1.26, 95 % CI 0.43-3.67, P = 0.672; c2c2/c1c2 versus c1c1: OR = 0.95, 95 % CI 0.78-1.16, P = 0.114; and c2c2 versus c1c2/c1c1: OR = 1.17, 95 % CI 0.41-3.36, P = 0.775). Therefore, the findings from this meta-analysis suggest that CYP2E1 rs2031920 polymorphism is associated with colorectal cancer risk, but CYP2E1 rs3813867 polymorphism is not associated with colorectal cancer risk. In addition, more well-designed studies with large sample size are needed to provide a more precise evaluation on the associations above.