Polymorphisms in the genes involved in the arachidonic acid-pathway, fish consumption and the risk of colorectal cancer

Interactions of Colorectal Cancer, Dietary Fats, and Polymorphisms of Arachidonate Lipoxygenase and Cyclooxygenase Genes: A Literature Review

Objective

Genetics and dietary factors play important roles in the development of colorectal cancer (CRC). However, the underlying mechanisms of the interactions between CRC, gene polymorphisms, and dietary fat are unclear. This review study investigated the effects of polymorphisms of arachidonate lipoxygenase (ALOX) and cyclooxygenase (COX) genes in the association between CRC and dietary fat.

Methods

All the related papers published from 2000 to 2022 were collected from different databases such as PubMed, Science Direct, Scopus, and Cochran using related keywords such as colorectal cancer, ALOX, COX, polymorphism, and dietary fat. Non-English and unrelated documents were excluded.

Results

Some single-nucleotide polymorphisms (SNPs) in the ALOX and COX genes, such as rs2228065, rs6413416, and rs4986832 in the ALOX gene, and rs689465 in the COX gene may play significant roles in the association between the risk of CRC and dietary fats. SNPs of ALOX and COX genes may influence the effects of dietary fatty acids on the risk of CRC.

Conclusion

Some polymorphisms of the ALOX and COX genes may have important roles in the effects of dietary fat on the risk of CRC. If future studies confirm these results, dietary recommendations for preventing colorectal cancer may be personalized based on the genotype of the ALOX and COX genes.

Multi-Omics Approach Points to the Importance of Oxylipins Metabolism in Early-Stage Breast Cancer

The involvement of oxylipins, metabolites of polyunsaturated fatty acids, in cancer pathogenesis was known long ago, but only the development of the high-throughput methods get the opportunity to study oxylipins on a system level. The study aimed to elucidate alterations in oxylipin metabolism as characteristics of breast cancer patients. We compared the ultra-high-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) oxylipin profile signatures in the blood plasma of 152 healthy volunteers (HC) and 169 patients with different stages of breast cancer (BC). To integrate lipidomics, transcriptomics, and genomics data, we analyzed a transcriptome of 10 open database datasets obtained from tissues and blood cells of BC patients and SNP data for 33 genes related to oxylipin metabolism. We identified 18 oxylipins, metabolites of omega-3 or omega-6 polyunsaturated fatty acids, that were differentially expressed between BCvsHC patients, including anandamide, prostaglandins and hydroxydocosahexaenoic acids. DEGs analysis of tissue and blood samples from BC patients revealed that 19 genes for oxylipin biosynthesis change their expression level, with CYP2C19, PTGS2, HPGD, and FAAH included in the list of DEGs in the analysis of transcriptomes and the list of SNPs associated with BC. Results allow us to suppose that oxylipin signatures reflect the organism's level of response to the disease. Our data regarding changes in oxylipins at the system level show that oxylipin profiles can be used to evaluate the early stages of breast cancer.

Fish Consumption and Colorectal Cancer Risk: Meta-Analysis of Prospective Epidemiological Studies and Review of Evidence from Animal Studies

Background: Epidemiological studies on the association between fish consumption and colorectal cancer (CRC) risk have yielded inconsistent results, despite evidence from preclinical studies that long-chain ω-3 polyunsaturated fatty acids inhibit colorectal carcinogenesis. We conducted a meta-analysis of prospective epidemiological studies investigating the association between fish consumption and CRC risk among humans and reviewed studies examining the link between fish components and colorectal carcinogenesis in animal models. Methods: We included studies published until November 2020. We calculated the summary risk ratio (SRR) and 95% confidence intervals (CI) through random effects meta-analysis models in order to summarize evidence from studies among humans. Results: Twenty-five prospective epidemiological studies encompassing 25,777 CRC cases were included. Individuals in the highest (vs. lowest) category of fish consumption had a significantly reduced risk of CRC (SRR 0.94, 95%CI 0.89-0.99). In dose-response meta-analysis, a 50-g increment in the daily consumption of fish was associated with a statistically significant 4% reduction in CRC risk (SRR 0.96, 95%CI 0.92-0.99). Preclinical studies (n = 25) identified multiple mechanisms of action of fish and fish components on colorectal carcinogenesis. Conclusions: Dietary recommendations for cancer prevention should take into account the evidence from epidemiological and preclinical studies that increasing fish consumption may be effective in preventing CRC.

Peroxisome Proliferator-Activated Receptor Gamma Pro12Ala/C161T Genotypes and Risky Haplotype Altering Risk of Breast Cancer: A Turkish Case-Control Study

Breast cancer (BC) has a high incidence rate among women worldwide, and the mechanisms and etiology of this disease are not yet fully understood. The peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear hormone receptor that plays important roles in energy metabolism and cellular differentiation, is also suggested to be effective in cancer development. However, the results of studies investigating the cancer association with PPARgamma are inconsistent, creating a need for further investigation of the effects of this transcription factor on BC risk. We have examined the Pro12Ala-(rs1801282) and C161T-(rs3856806) polymorphisms of the PPARgamma gene in Turkish patients with BC in this case-control study. A total of 95 women diagnosed with BC as cases and 119 controls were genotyped for PPARgamma polymorphisms by polymerase chain reaction and restriction fragment length polymorphism techniques. The ProPro genotype and T161 allele were associated with an increased risk of BC comparing with the Ala12 allele and CC161 genotype, respectively (p < 0.001). The multivariate regression analysis confirmed that the ProPro genotype (p < 0.011), T161 allele (p < 0.001), smoking (p = 0.019), and advanced age (> 60 years) (p = 0.007) are risk factors for breast cancer. We also found that the PPARgamma Pro12Ala and C161T polymorphisms were in linkage disequilibrium (D':0.511, r²:0.099). It was determined that carrying ProPro-T161 risky PPARgamma haplotype was associated with a higher risk of BC compared to protective Ala12-CC161 haplotype (p < 0.01, OR:7.797, 95% CI:3.521-17.263). We concluded that PPARgamma Pro12Ala and C161T polymorphisms are associated with increased BC risk, and ProPro-T161 risky haplotype, which is in linkage disequilibrium, increases this effect.

Dynamic Connectivity Alteration Facilitates Cognitive Decline in Alzheimer's Disease Spectrum

Introduction: It is unknown the alterations in the dynamic networks of the brain and the underlying molecular pathological mechanism of Alzheimer's disease (AD) spectrum. Here, we aim to explore the association between alterations in the dynamic brain networks' trajectory and cognitive decline in the AD spectrum. Methods: One hundred sixty subjects were recruited from the ADNI database, including 49 early mild cognitive impairment, 28 late mild cognitive impairment, 24 AD patients, and 59 cognitively normal. All participants completed the resting-state functional magnetic resonance imaging scan and neuropsychological tests. We integrated a new method combining large-scale network analysis and canonical correlation analysis to explore the dynamic spatiotemporal patterns within- and between resting-state networks (RSNs) and their significance in the AD spectrum. Results: All RSNs represented an increase in connectivity within networks by enhancing inner cohesive ability, while 7 out of 10 RSNs were characterized by a decrease in connectivity between networks, which indicated a weakened connector among networks from the early stage to dementia. This dichotomous mode presenting large-scale dynamic network abnormality was significantly correlated with the levels of molecular biomarkers of AD, and cognitive performance, as well as with the accumulating effects of 10 identified AD-related genetic risk factors. Discussion: These findings deepen our understanding of the associated mechanism underlying large-scale network disruption, linking known molecular biomarkers and phenotypic variations in the AD spectrum.

COX-2 gene rs689466 polymorphism is associated with increased risk of colorectal cancer among Caucasians: a meta-analysis

BACKGROUND

Several studies have reported the Cyclooxygenase 2 (COX-2) rs689466 polymorphism as a susceptibility locus of colorectal cancer (CRC), but their findings are inconsistent. Thus, this meta-analysis was performed to more accurately identify the effects of this polymorphism on CRC risk.

METHODS

Potential case-control studies on EMBASE, Google Scholar, Web of Science, Cochrane Library, and PubMed were searched. The strength of association was quantified by pooled odds ratio and 95% confidence interval. Totally 16 articles involving 8998 cases and 11,917 controls were included.

RESULTS

None of the five tested genetic models revealed an association between rs689466 polymorphism and CRC risk. Stratified analysis by ethnicity uncovered a positive association between this polymorphism and higher CRC risk in Caucasians, but not in Asians. In addition, we found that high expression of COX-2 was associated with better overall survival for all CRC patients.

CONCLUSION

To sum up, the COX-2 rs689466 polymorphism may be related with susceptibility to CRC in Caucasians. This finding should be verified by larger-size studies with different ethnic groups.

MicroRNA-binding site polymorphisms and risk of colorectal cancer: A systematic review and meta-analysis

Genetic variations in miRNAs binding site might participate in cancer risk. This study aimed to systematically review the association between miRNA-binding site polymorphisms and colorectal cancer (CRC). Electronic literature search was carried out on PubMed, Web of Science (WOS), Scopus, and Embase. All types of observational studies till 30 November 2018 were included. Overall 85 studies (21 SNPs) from two systematic searches were included analysis. The results showed that in the Middle East population, the minor allele of rs731236 was associated with decreased risk of CRC (heterozygote model: 0.76 [0.61-0.95]). The minor allele of rs3025039 was related to increased risk of CRC in East Asian population (allelic model: 1.25 [1.01-1.54]). Results for rs3212986 were significant in overall and subgroup analysis (P < .05). For rs1801157 in subgroup analysis the association was significant in Asian populations (including allelic model: 2.28 [1.11-4.69]). For rs712, subgroup analysis revealed a significant (allelic model: 1.41 [1.23-1.61]) and borderline (allelic model: 0.92 [0.84-1.00]) association in Chinese and Czech populations, respectively. The minor allele of rs17281995 increased risk of CRC in different genetic models (P < .05). Finally, rs5275, rs4648298, and rs61764370 did not show significant associations. In conclusion, minor allele of rs3025039, rs3212986, and rs712 polymorphisms increases the risk of CRC in the East Asian population, and heterozygote model of rs731236 polymorphism shows protective effect in the Middle East population. In Europeans, the minor allele of rs17281995 may increase the risk of CRC, while rs712 may have a protective effect. Further analysis based on population stratifications should be considered in future studies.

PPARG rs3856806 C>T Polymorphism Increased the Risk of Colorectal Cancer: A Case-Control Study in Eastern Chinese Han Population

Purpose: Functional variants in the peroxisome proliferator-activated receptor gamma (PPARG) and PPARG co-activator 1 (PPARGC1) family (e.g., PPARGC1A and PPARGC1B) genes were predicted to confer susceptibility to colorectal cancer (CRC). The aim of the present study was to explore the relationship between PPARG, PPARGC1A, PPARGC1B polymorphism and the risk of CRC.

Patients and methods: We conducted a case-control study with 1,003 CRC cases and 1,303 controls. We selected the PPARG rs3856806 C>T, PPARGC1A rs2970847 C>T, rs8192678 C>T, rs3736265 G>A and PPARGC1B rs7732671 G>C and rs17572019 G>A SNPs to assess the relationship between PPARG, PPARGC1A, PPARGC1B their variants and risk of CRC.

Results: We found that the PPARG rs3856806 C>T polymorphism increased the risk of CRC (TT vs. CC: adjusted OR, 1.59, 95% CI 1.08–2.35, P = 0.020; TT/CT vs. CC: adjusted OR, 1.26; 95% CI 1.06–1.49; P = 0.009 and TT vs. CC/CT: adjusted OR, 1.54; 95% CI 1.05–2.26; P = 0.028), even after a Bonferroni correction test. The stratified analysis revealed that the PPARG rs3856806 C>T polymorphism also increased the risk of CRC, especially in male, ≥61 years old, never smoking, never drinking, BMI ≥ 24 kg/m², colon cancer and rectum cancer subgroups.

Conclusion: Our findings highlight that the PPARG rs3856806 C>T polymorphism may increase the risk of CRC. In the future larger sample size case-control studies with a detailed functional assessment are needed to further determine the relationship of the PPARG rs3856806 C>T polymorphism with CRC risk.

Association between cyclooxygenase-2 (COX-2) 8473 T > C polymorphism and cancer risk: a meta-analysis and trial sequential analysis

Background

Numerous studies have investigated the relationship between COX-2 8473 T > C polymorphism and cancer susceptibility, however, the results remain controversial. Therefore, we carried out the present meta-analysis to obtain a more accurate assessment of this potential association.

Methods

In this meta-analysis, 79 case-control studies were included with a total of 38,634 cases and 55,206 controls. We searched all relevant articles published in PubMed, EMBASE, OVID, Web of Science, CNKI and Wanfang Data, till September 29, 2017. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were used to evaluate the strength of the association. We performed subgroup analysis according to ethnicity, source of controls, genotyping method and cancer type. Moreover, Trial sequential analysis (TSA) was implemented to decrease the risk of type I error and estimate whether the current evidence of the results was sufficient and conclusive.

Results

Overall, our results indicated that 8473 T > C polymorphism was not associated with cancer susceptibility. However, stratified analysis showed that the polymorphism was associated with a statistically significant decreased risk for nasopharyngeal cancer and bladder cancer, but an increased risk for esophageal cancer and skin cancer. Interestingly, TSA demonstrated that the evidence of the result was sufficient in this study.

Conclusion

No significant association between COX-2 8473 T > C polymorphism and cancer risk was detected.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4753-3) contains supplementary material, which is available to authorized users.

Single nucleotide polymorphism rs4648298 in miRNAs hsa-miR21 and hsa-miR590 binding site of COX gene is a strong colorectal cancer determinant

Background

Genetic determinants are considered as driving forces in development colorectal cancer (CRC), a malignancy that ranks as the second cause of cancer death in the world. Single nucleotide polymorphisms (SNPs), are considered as the main genetic factor in cancers susceptibility. MicroRNAs are critical players in posttranslational gene regulation by binding to their specific recognition sequences located at 3' untranslated region (UTR) of mRNAs. In present study we have elucidated the role of 9,850 A > G (rs4648298), in development of sporadic CRC in Iranian population.

Methods

A case-control study using 88 CRC patients and 88 noncancerous counterparts was undertaken in order to determine rs4648298 genotypes using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Also, a meta-analysis was performed based on 9 articles accessed via the MEDLINE, Cochrane review, Google Scholar and Scopus databases.

Results

AA genotype was determined to be associated with significant decreased risk of CRC in our study population [odds ratio (OR) =0.14; 95% confidence interval (CI), 0.05-0.34; P<0.001]. In a meta-analysis on 6 risk estimates for the AG versus AA genotype, we found a significant inverse association between AG SNPs and risk of gastric adenocarcinoma, CRC, breast cancer and prostate cancer (OR =0.86; 95% CI, 0.76-0.98; P<0.02).

Conclusions

Our results suggest significant correlation between rs4648298 polymorphism and CRC risk in Iranian population.

PPARG c.1347C>T polymorphism is associated with cancer susceptibility: from a case-control study to a meta-analysis

Recently, several studies suggested that PPARG c.1347C>T polymorphism was correlated with cancer risk. However, past results remained controversial. In this study, we performed a case-control study on the relationship of PPARG c.1347C>T polymorphism with risk of non-small cell lung cancer (NSCLC) and subsequently carried out a meta-analysis to further assess the association between PPARG c.1347C>T and overall cancer. In our case-control study, after adjusting by age, sex, body mass index (BMI), smoking and drinking, a tendency to increased NSCLC risk was noted (CT/TT vs. CC: adjusted OR, 1.21; 95% CI, 0.97–1.51; P = 0.097). In the meta-analysis, we found a significant association between PPARG c.1347C>T polymorphism and overall cancer risk (T vs. C: OR, 1.13; 95% CI, 1.03–1.23; P = 0.006; TT vs. CC: OR, 1.29; 95% CI, 1.07–1.56; P = 0.008, CT/TT vs. CC: OR, 1.11; 95% CI, 1.02–1.21; P = 0.014 and TT vs. CT/CC: OR, 1.26; 95% CI, 1.04–1.52; P = 0.016). In a subgroup analysis by ethnicity, evidence of significant association between PPARG c.1347C>T polymorphism and cancer risk was found among Asians and mixed populations. In a subgroup analysis by cancer type, PPARG c.1347C>T polymorphism was associated with risk of esophageal cancer and glioblastoma. In addition, in a subgroup analysis by origin of cancer cell, evidence of significant association between PPARG c.1347C>T polymorphism and cancer risk was also found among epithelial tumor. In conclusion, the findings indicate PPARG c.1347C>T polymorphism may increase the susceptibility of cancer.

Association of PPARG rs 1801282 C>G polymorphism with risk of colorectal cancer: from a case-control study to a meta-analysis

The functional single nucleotide polymorphisms in peroxisome proliferator-activated receptor gamma (PPARG) gene were predicted to be correlated with the susceptibility of colorectal cancer (CRC). The aim of the present study was to explore the relationship between PPARG rs1801282 C>G polymorphism and the risk of CRC. First, we conducted a case-control study with 387 CRC cases and 1,536 controls. We used the SNPscan method to determine the genotypes of PPARG rs1801282 C>G polymorphism. We found PPARG rs1801282 C>G polymorphism had a tendency of decreased risk to CRC risk (CG vs. CC: adjusted OR, 0.67, 95% CI = 0.43–1.04 for CG vs. CC, P = 0.073; GG vs. CC: adjusted OR, 0.68; 95% CI, 0.44–1.05; P = 0.078). The stratified analysis revealed PPARG rs1801282 C>G polymorphism also had a tendency of decreased risk to colon cancer (CG vs. CC: adjusted OR = 0.54, 95% CI = 0.27–1.08, P = 0.083). The results of subsequent meta-analysis suggested that PPARG rs1801282 C>G polymorphism might be a protective factor for CRC, especially in Asians, colon cancer and rectum cancer subgroups. In conclusion, our study indicates that PPARG rs1801282 C>G polymorphism might decrease the risk of overall CRC. Larger sample size and well-designed case-control studies are needed to confirm the potential association.

Cyclooxygenase-2 gene polymorphisms and susceptibility to colorectal cancer in a Brazilian population

BACKGROUND

Multi-ethnicity of Brazilian population displays high levels of genomic diversity. Polymorphism may detect people at higher risk of developing cancer, distinctive response to treatment, and prognosis. Cyclooxygenase-2 (COX-2) is induced in response to growth factors and cytokines, and is expressed in inflammatory diseases, precancerous lesions and colorectal cancer (CRC). The aim of this study was to evaluate the influence of COX-2 -1195A > G and 8473T > C polymorphisms as a risk factor of developing CRC.

METHODS

We evaluated COX-2 Single Nucleotide Polymorphism (SNP) of 230 CRC patients and 196 healthy controls by Real-Time Polymerase Chain Reaction.

RESULTS

Populations were in Hardy-Weinberg equilibrium (HWE), except for control group of 8473T > C SNP. The frequencies were similar in both groups for genotypes and haplotypes. There was no association between studied polymorphisms and risk of CRC.

CONCLUSIONS

The gene polymorphisms studied do not participate in the genetic susceptibility to CRC in a Brazilian population.

Association between COX-2 -1195G>A polymorphism and gastrointestinal cancer risk: A meta-analysis

AIM

To perform a meta-analysis to investigate the association between cyclooxygenase-2 (COX-2) -1195G>A gene polymorphism and gastrointestinal cancers.

METHODS

Publications related to the COX-2 -1195G>A gene polymorphism and gastrointestinal cancers published before July 2016 were retrieved from PubMed, EMBASE, Web of Science, China Biological Medicine Database, China National Knowledge Infrastructure, and CQVIP Database. Meta-analysis was performed using Stata11.0 software. The strength of the association was evaluated by calculating the combined odds ratios (ORs) and the corresponding 95%CIs. The retrieved publications were excluded or included one by one for sensitivity analysis. In addition, the funnel plot, Begg’s rank correlation test, and Egger’s linear regression method were applied to analyse whether the included publications had publication bias.

RESULTS

A total of 24 publications related to the COX-2 -1195G>A gene polymorphism were included, including 28 studies involving 11043 cases and 18008 controls. The meta-analysis results showed that the COX-2 -1195G>A gene polymorphism significantly correlated with an increased risk of gastrointestinal cancers, particularly gastric cancer (A vs G: OR = 1.35; AA/AG vs GG: OR = 1.54; AA vs GG/AG: OR = 1.43; AA vs GG: OR = 1.80; AG vs GG: OR = 1.35). Compared to the Caucasian population in America and Europe, the COX-2 -1195G>A gene polymorphism in the Asian population (A vs G: OR = 1.30; AA/AG vs GG: OR = 1.50; AA vs GG/AG: OR = 1.35; AA vs GG: OR = 1.71; AG vs GG: OR = 1.37) significantly increased gastrointestinal cancer risk. The sensitivity analysis (P < 0.05) and the false positive report probability (P < 0.2) confirmed the reliability of the results.

CONCLUSION

The results showed that the COX-2 -1195G>A gene polymorphism might be a potential risk factor for gastrointestinal cancers. Further validation by a large homogeneous study is warranted.

The prostaglandin synthase 2/cyclooxygenase 2 (PTGS2/ COX2) rs5277 polymorphism does not influence risk of colorectal cancer in an Iranian population

BACKGROUND

The prostaglandin-endoperoxide synthase 2 [PTGS2, commonly known as cyclooxygenase-2 (COX-2)] is an enzyme induced by proinflammatory stimuli that is often overexpressed in malignant tissue and involved in the synthesis of prostaglandins and thromboxanes, regulators of processes such as inflammation, cell proliferation, and angiogenesis, all relevant for cancer development. We investigated whether a functional genetic polymorphism, rs5277, in COX-2 may have a risk-modifying effect on sporadic colorectal cancer in an Iranian population.

MATERIALS AND METHODS

We conducted a case-control study on 167 patients with colorectal cancer and 197 cancer-free controls in Taleghani Hospital in Tehran, Iran, between 2007 and 2011. Peripheral blood samples of both groups were processed for DNA extraction and genotyping of the COX-2 gene polymorphism (rs5277) using PCR-RFLP. RFLP results were confirmed by direct sequencing. Logistic regression analysis was performed to calculate the adjusted odds ratio (OR) and 95% confidence interval (95% CI).

RESULTS

There was no significant difference in the distribution of COX-2 gene rs5277 polymorphism genotype and the allelic form, among CRC patients compared with the healthy control group (p: 0.867).

CONCLUSIONS

Our results suggest that rs5277 polymorphism in COX2 could not be a good prognostic indicator for patients with CRC.

Polymorphisms in arachidonic acid metabolism-related genes and the risk and prognosis of colorectal cancer

Cyclooxygenase-2 (COX-2), 12-lipoxygenase (12-LOX) and phospholipaseA2 (PLA2) played important roles in the modulation of apoptosis, angiogenesis, carcinogenesis and invasion of colorectal cancer (CRC). The polymorphisms in COX-2, 12-LOX and PLA2 may affect their roles. Therefore, we investigated if COX-2 -1195G > A, 12-LOX 261Arg > Gln and PLA2 c.349 + 191A > G polymorphisms were associated with risk and prognosis of CRC as well as possible interactions with the environmental factors on the risk of CRC in Northeast of China. A case-control study with 451 cases and 631 controls were carried out, a cohort with 386 patients were followed up. Genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Compared with the 261Arg/Arg genotype, 12-LOX 261Arg/Gln genotype and 261Arg/Gln + Gln/Gln genotypes reduced the risk of rectal cancer by 33% (adjusted OR = 0.67, 95% CI 0.47-0.97, p = 0.03) and 32% (adjusted OR = 0.68, 95% CI 0.49-0.96, p = 0.03), respectively. The adjusted HR for the association between 12-LOX 261Gln/Gln genotype and overall survival in patients with CRC was 1.68 (95% CI 1.06-2.68, p = 0.03). There was also evidence of an interaction between the PLA2 c.349 + 191 A > G genotypes and the overnight food consumption (adjusted ORi = 1.92, 95% CI 1.14-3.25, P(interaction) = 0.01). These observations indicate that 12-LOX 261Arg > Gln polymorphism may affect risk of rectal cancer, and it may be a potential predictive marker for prognosis of CRC.

Meta-analysis of the association between COX-2 polymorphisms and risk of colorectal cancer based on case-control studies

OBJECTIVE

Cyclooxygenase-2 (COX-2) is an inducible enzyme converting arachidonic acid to prostaglandins and playing important roles in inflammatory diseases as well as tumor development. Previous studies investigating the association between COX-2 polymorphisms and colorectal cancer (CRC) risk reported conflicting results. We performed a meta-analysis of all available studies to explore this association.

METHODS

All studies published up to October 2013 on the association between COX-2 polymorphisms and CRC risk were identified by searching electronic databases PubMed, EMBASE, and Cochrane library. The association between COX-2 polymorphisms and CRC risk was assessed by odds ratios (ORs) together with their 95% confidence intervals (CIs).

RESULTS

Ten studies with 6,774 cases and 9,772 controls were included for -1195A>G polymorphism, 13 studies including 6,807 cases and 10,052 controls were available for -765G>C polymorphism, and 8 studies containing 5,121 cases and 7,487 controls were included for 8473T>C polymorphism. With respect to -765G>C polymorphism, we did not find a significant association with CRC risk when all eligible studies were pooled into the meta-analysis. However, in subgroup analyses by ethnicity and cancer location, with a Bonferroni corrected alpha of 0.05/2, statistical significant increased CRC risk was found in the Asian populations (dominant model CC+CG vs. GG: OR = 1.399, 95%CI: 1.113-1.760, P = 0.004) and rectum cancer patients (CC vs. GG: OR = 2.270, 95%CI: 1.295-3.980, P = 0.004; Recessive model CC vs. CG+GG: OR = 2.269, 95%CI: 1.297-3.970, P = 0.004). In subgroup analysis according to source of control, no significant association was detected. With respect to -1195A>G and 8473T>C polymorphisms, no significant association with CRC risk was demonstrated in the overall and subgroup analyses.

CONCLUSIONS

The present meta-analysis suggests that the COX-2 -765G>C polymorphism may be a risk factor for CRC in Asians and rectum cancer patients. Further large and well-designed studies are needed to confirm this association.

Cyclooxygenase-2 polymorphisms and susceptibility to colorectal cancer: a meta-analysis

PURPOSE

Four polymorphisms, -765G>C, -1195G>A, 8473T>C, and Val511Ala, in the cyclooxygenase-2 (COX-2) gene were identified to be associated with colorectal cancer (CRC) risk. However, the results are inconsistent. The objective of this meta-analysis was to evaluate the association between these four polymorphisms and the risk of CRC.

MATERIALS AND METHODS

All eligible case-control studies published up to December 2012 on the association between the four polymorphisms of COX-2 and CRC risk were identified by searching PubMed and Web of Science. The CRC risk associated with the four polymorphisms of the COX-2 gene was estimated for each study by odds ratio (OR) together with its 95% confidence interval (CI), respectively.

RESULTS

A total of 15 case-control studies were included. Overall, no evidence has indicated that the -1195A allele, -765C allele, 8473C allele, and 511Ala allele are associated with susceptibility to CRC (-1195G>A: OR=1.11, 95% CI: 0.82-1.51, p=0.78; -765G>C: OR=1.08, 95% CI: 0.96-1.21, p=0.07; 8473T>C: OR=1.03, 95% CI: 0.89-1.18, p=0.91; Val511Ala: OR=0.71, 95% CI: 0.46-1.09, p=0.94). However, stratified analysis with ethnicity indicated that individuals with -765GC or GC/CC genotypes had an increased risk of CRC among Asian populations (GC vs. GG: OR=1.05, 95% CI: 0.87-1.28, p=0.03; GC+CC vs. GG: OR=1.08, 95% CI: 0.96-1.21, p=0.07).

CONCLUSION

This meta-analysis indicated that -765G>C polymorphism was significantly associated with susceptibility to CRC in Asian populations.

An association between the PTGS2 rs5275 polymorphism and colorectal cancer risk in families with inherited non-syndromic predisposition

Recently our group completed a genome-wide linkage study investigating Australian and Spanish families with inherited risk of colorectal cancer (CRC). A minor linkage peak from that study located on chromosome 1 correlates with the location of a known CRC risk-modifying gene, prostaglandin synthase (PTGS2). PTGS2 encodes the inducible prostaglandin synthase enzyme cyclooxygenase-2 (COX-2). Prostaglandins are implicated in the initiation of carcinogenesis and progression of tumours. Sequencing of PTGS2 in a small subset of affected individuals identified a high frequency of the minor C allele of single nucleotide polymorphism rs5275. We then genotyped the rs5275 polymorphism in 183 affected and 223 unaffected individuals from our CRC predisposed families. Tests for association in the presence of linkage were made using family-based association tests. The C allele was found to be significantly associated (P<0.01) with diagnosis of hereditary non-syndromic CRC (P=0.0094, dominant model) and an earlier age of diagnosis (P=0.0089, heterozygous-advantage model). Interestingly, by stratifying the age of diagnosis data, we observed a speculative gender-discordant effect. Relative to other groups, female CC carriers were diagnosed less when young, but by 60 years of age were the most at risk group. Conversely, CT carriers of both genders showed a consistently earlier diagnosis relative to TT carriers. Our results suggest potential differential age-and gender-dependent efficacies of chemopreventative COX-2 inhibitors in the context of non-syndromic colorectal cancer.

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

BACKGROUND

Diet contributes significantly to colorectal cancer (CRC) aetiology and may be potentially modifiable.

AIM

To review diet-gene interactions, aiming to further the understanding of the underlying biological pathways in CRC development.

METHODS

The PubMed and Medline were systematically searched for prospective studies in relation to diet, colorectal cancer and genetics.

RESULTS

In a meta-analysis, no interaction between NAT1 phenotypes and meat intake in relation to risk of CRC was found (P-value for interaction 0.95). We found a trend towards interaction between NAT2 phenotypes and meat intake in relation to risk of CRC. High meat intake was not associated with risk of CRC among carriers of the slow NAT2 phenotype, whereas NAT2 fast acetylators with high meat intake were at increased risk of CRC (OR = 1.25; 95% confidence interval (CI): 0.92-2.01) compared with slow acetylators with low meat intake (reference), P-value for interaction = 0.07. Low meat intake in the studied populations may influence the result. Interactions between meat, cruciferous vegetables, fibres, calcium, vitamins, and alcohol and ABCB1, NFKB1, GSTM1, GSTT1, CCND1, VDR, MGTM, IL10 and PPARG are suggested.

CONCLUSIONS

A number of interactions between genetic variation and diet are suggested, but the findings need replication in independent, prospective, and well-characterised cohorts before conclusions regarding the underlying biological mechanisms can be reached. When the above criteria are met, studies on diet-gene interactions may contribute valuable insight into the biological mechanisms underlying the role of various dietary items in colorectal carcinogenesis.

Relationship between polymorphisms in the promoter region of the COX-2 gene and susceptibility to colorectal cancer

AIM: To investigate the correlation between polymorphisms in the promoter region (-1195G/A, rs689466) and 3'-untranslated region (8473T/C, rs5275) of the cyclooxygenase-2 (COX-2) gene and risk of colorectal cancer (CRC).

METHODS: A case-control study was performed in 343 patients with CRC and 340 healthy individuals. The polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) method was used to genotype the COX-2-1195G/A and COX-2-8473T/C polymorphisms. The SPSS 10.0 software was used to analyze genotypic and allelic frequencies.

RESULTS: We found no differences in allele or genotype distributions of COX-2-8473T/C between cases and controls (all P > 0.05). However, there was an obvious difference in the polymorphism distribution of COX-2-1195G/A between the CRC group and control group (P < 0.001). Stratification analysis revealed a significantly increased risk in CRC patients carrying the AG genotype (adjusted OR = 2.23; 95% CI 1.50-3.32), AA genotype (adjusted OR = 2.46; 95% CI 1.51-4.02) or (AG/AA) genotype (adjusted OR = 2.27; 95% CI 1.55-3.34) compared to the control group. There was no difference in the distribution of each COX-2 genotype between colon and rectal cancer. Patients carrying the COX-2-1195A allele had a higher risk of lymph node metastasis and CRC progression.

CONCLUSION: COX-2-1195AG/AA genotype is associated with a higher risk of CRC, lymph node metastasis and CRC progression.

PTGS1, PTGS2, ALOX5, ALOX12, ALOX15, and FLAP SNPs: interaction with fatty acids in colon cancer and rectal cancer

Dietary polyunsaturated fatty acids (PUFAs) can be converted to prostaglandins and leukotrienes. Oxygenation of omega-6 PUFAs generally results in the production of pro-inflammatory mediators, whereas oxygenated products of omega-3 (n-3) PUFAs generally have lower inflammatory activity. We hypothesize that elevated n-3 PUFA intakes from fish are associated with lower risk of colorectal cancer among those with genetic variants that result in higher levels of pro-inflammatory mediators. In population-based case-control studies of colon (case n = 1,574) and rectal cancer (case n = 791) and disease-free controls (n = 2,969), we investigated interactions between dietary fatty acid intake and 107 candidate polymorphisms and tagSNPs in PTGS1, PTGS2, ALOX12, ALOX5, ALOX15, and FLAP. The two studies used an identical genotyping protocol. We observed interactions and statistically significant increases in colon cancer risk for low docosahexaenoic acid intake among those with the PTGS1 rs10306110 (-1,053 A > G) variant genotypes (OR = 1.6, 95 % confidence interval = 1.1-2.3, adj. p = 0.06) and rectal cancer risk for low total fat intake among those with the variant PTGS1 rs10306122 (7,135 A > G) (OR(vs.wt) = 1.80, 1.02-2.99; adj. p = 0.08). The ALOX15 rs11568131 (10,339 C > T) wild type in combination with a high inflammation score (low EPA intake, high AA intake, no regular NSAID use, high BMI, smoking) was associated with increased colon cancer risk (OR = 2.28, 1.7-3.07). Rectal cancer risk was inversely associated with a low inflammation score among PTGS2 rs4648276 (3,934 T > C) variant allele carriers (OR = 0.49, 0.25-0.75). Overall, these data provide some modest evidence for interactions between dietary fat intake and genetic variation in genes involved in eicosanoid metabolism and colorectal cancer risk.

Epigenetic deregulation of the COX pathway in cancer

Inflammation is a major cause of cancer and may condition its progression. The deregulation of the cyclooxygenase (COX) pathway is implicated in several pathophysiological processes, including inflammation and cancer. Although, its targeting with nonsteroidal antiinflammatory drugs (NSAIDs) and COX-2 selective inhibitors has been investigated for years with promising results at both preventive and therapeutic levels, undesirable side effects and the limited understanding of the regulation and functionalities of the COX pathway compromise a more extensive application of these drugs. Epigenetics is bringing additional levels of complexity to the understanding of basic biological and pathological processes. The deregulation of signaling and biosynthetic pathways by epigenetic mechanisms may account for new molecular targets in cancer therapeutics. Genes of the COX pathway are seldom mutated in neoplastic cells, but a large proportion of them show aberrant expression in different types of cancer. A growing body of evidence indicates that epigenetic alterations play a critical role in the deregulation of the genes of the COX pathway. This review summarizes the current knowledge on the contribution of epigenetic processes to the deregulation of the COX pathway in cancer, getting insights into how these alterations may be relevant for the clinical management of patients.

The Cox-2 -1195 G > A polymorphism and cancer risk: a meta-analysis of 25 case-control studies

Cyclooxygenase 2 (Cox-2, a rate-limiting enzyme in the conversion of arachidonic acid to prostanoids) has been implicated in several physiological and pathological processes, and it has been reported that polymorphisms in the regulatory region of Cox-2 might influence its expression, contributing to the interindividual susceptibility to cancer. However, results from published studies on the association between the Cox-2 -1195G > A polymorphism and the risk of cancer are conflicting. We performed a meta-analysis based on 25 case-control studies, including a total of 9482 cancer cases and 12 206 controls to derive a more precise estimation of the association and its possible influence on cancer risk. We used odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of the association. The overall results indicated that the variant genotypes moderately increased risk of cancer (AA/AG versus GG, OR = 1.15, 95% CI: 1.02-1.31). In the stratified analysis for the -1195G > A polymorphism, a proximate association was observed in Asian populations (AA/AG versus GG, OR = 1.28, 95% CI: 1.12-1.46), but no significant association except for oesophageal cancer and 'others' was found when stratified by cancer type. In conclusion, our meta-analysis indicates that -1195G > A of Cox-2 is a low penetration risk factor for cancer.

Cyclooxygenase-2 (COX-2) polymorphisms and risk of inflammatory bowel disease in a Scottish and Danish case-control study

BACKGROUND

Inflammatory bowel diseases (IBDs) are a result of interactions between luminal pathogens and the intestinal immune response. Cyclooxygenase-2 (COX-2) plays a key role in the regulation of the inflammatory response upon stimulation by luminal pathogens via Toll-like receptors.

METHODS

Genotypes of the COX-2/PTGS2/PGHS2 A-1195G (rs689466), G-765C (rs20417), and T8473C (rs5275) polymorphisms were assessed in a Scottish and Danish case-control study including 732 Crohn's disease (CD) cases, 973 ulcerative colitis (UC) cases, and 1157 healthy controls using logistic regression.

RESULTS

Carriers of the COX-2 A-1195G variant allele had increased risk of UC (odds ratio [OR], 95% confidence interval [CI] = 1.25 [1.02-1.54], P = 0.03) and of both UC and IBD among never smokers (OR [95% CI] = 1.47 [1.11-1.96], P = 0.01 and OR [95% CI] = 1.37 [1.06-1.77], P = 0.02, respectively). Furthermore, this variant genotype was associated with increased risk of diagnosis of UC before age 40 years and with extensive UC (OR [95% CI] = 1.34 [1.11-1.62], P = 0.002 and OR [95% CI] = 1.32 [1.03-1.69], P = 0.03, respectively).

CONCLUSIONS

COX-2 A-1195G polymorphism was associated with the risk of UC, especially among never-smokers, suggesting that low activity of COX-2 may predispose to UC. Our results suggest that inclusion of smoking status may be essential for the evaluation of the role of genetic predisposition to IBD.

Polymorphisms in regulatory regions of cyclooxygenase-2 gene and breast cancer risk in Brazilians: a case-control study

Background

Cyclooxygenase-2 (COX-2) is up-regulated in several types of cancer, and it is hypothesized that COX-2 expression may be genetically influenced. Here, we evaluate the association between single-nucleotide polymorphisms (SNPs) in the COX-2 gene (PTGS2) and the occurrence of breast cancer among Brazilian women.

Methods

The study was conducted prospectively in two steps: First, we screened the promoter region and three fragments of the 3'-untranslated region of PTGS2 from 67 healthy Brazilians to identify SNPs and to select those with a minor allele frequency (MAF) of at least 0.10. The MAF of these selected SNPs was further characterized in 402 healthy volunteers to evaluate potential differences related to heterogeneous racial admixture and to estimate the existence of linkage disequilibrium among the SNPs. The second step was a case-control study with 318 patients and 273 controls designed to evaluate PTGS2 genotype- or haplotype-associated risk of breast cancer.

Results

The screening analysis indicated nine SNPs with the following MAFs: rs689465 (0.22), rs689466 (0.15), rs20415 (0.007), rs20417 (0.32), rs20419 (0.015), rs5270 (0.02), rs20424 (0.007), rs5275 (0.22) and rs4648298 (0.01). The SNPs rs689465, rs689466, rs20417 and rs5275 were further studied: Their genotypic distributions followed Hardy-Weinberg equilibrium and the MAFs were not affected by gender or skin color. Strong linkage disequilibrium was detected for rs689465, rs20417 and rs5275 in the three possible pairwise combinations. In the case-control study, there was a significant increase of rs5275TC heterozygotes in cases compared to controls (OR = 1.44, 95% CI = 1.01-2.06; P = 0.043), and the haplotype formed by rs689465G, rs689466A, rs20417G and rs5275C was only detected in cases. The apparent association with breast cancer was not confirmed for rs5275CC homozygotes or for the most frequent rs5275C-containing haplotypes.

Conclusions

Our results indicate no strong association between the four most frequent PTGS2 SNPs and the risk of breast cancer.

Polymorphic human prostaglandin H synthase-2 proteins and their interactions with cyclooxygenase substrates and inhibitors

The cyclooxygenase (COX) activity of prostaglandin H synthase-2 (PGHS-2) is implicated in colorectal cancer and is targeted by nonsteroidal anti-inflammatory drugs (NSAIDs) and dietary n-3 fatty acids. We used purified, recombinant proteins to evaluate the functional impacts of the R228H, E488G, V511A and G587R PGHS-2 polymorphisms on COX activity, fatty acid selectivity and NSAID actions. Compared to wild-type PGHS-2, COX activity with arachidonate was ∼20% lower in 488G and ∼20% higher in 511A. All variants showed time-dependent inhibition by the COX-2-specific inhibitor (coxib) nimesulide, but 488G and 511A had 30-60% higher residual COX activity; 511A also showed up to 70% higher residual activity with other time-dependent inhibitors. In addition, 488G and 511A differed significantly from wild type in Vmax values with the two fatty acids: 488G showed ∼20% less and 511A showed ∼20% more discrimination against eicosapentaenoic acid. The Vmax value for eicosapentaenoate was not affected in 228H or 587R, nor were the Km values or the COX activation efficiency (with arachidonate) significantly altered in any variant. Thus, the E488G and V511A PGHS-2 polymorphisms may predict who will most likely benefit from interventions with some NSAIDs or n-3 fatty acids.

Potentially functional COX-2-1195G>A polymorphism increases the risk of digestive system cancers: a meta-analysis

BACKGROUND AND AIM

Three potentially functional polymorphisms: -765G>C, -1195G>A, and 8473T>C in the cyclooxygenase-2 (COX-2) gene were identified and proposed to be associated with cancer susceptibility. The aim of this meta-analysis was to evaluate the association between these three polymorphisms and the risk of cancer in diverse populations.

METHODS

All case-control studies published up to November 2009 on the association between the three polymorphisms of COX-2 and cancer risk were identified by searching PubMed. The cancer risk associated with the three polymorphisms of the COX-2 gene was estimated for each study by OR together with its 95% confidence interval (CI), respectively.

RESULTS

A total of 47 case-control studies were included, and variant genotypes GA/AA of -1195G>A were associated with a significantly increased cancer risk (GA/AA vs GG: odds ratio [OR], 1.29; 95% CI, 1.18-1.41; P(heterogeneity) = 0.113), and this significant association was mainly observed within cancers of the digestive system (e.g. colorectal, gastric, esophageal, oral, biliary tract, gallbladder, and pancreatic) without between-study heterogeneity (GA/AA vs GG: OR, 1.36; 95% CI; 1.23-1.51; P(heterogeneity) = 0.149). Furthermore, a stratification analysis showed that the risk of COX-2-1195G>A associated with cancers in the digestive system was more evident among Asians than Caucasians. However, for COX-2-765G>C and 8473T>C, no convincing association between the two polymorphisms and risk of cancer or cancer type was observed.

CONCLUSIONS

The effect of three potentially functional polymorphisms (-765G>C, -1195G>A, and 8473T>C) in the COX-2 gene on cancer risk provided evidence that the COX-2-1195G>A polymorphism was significantly associated with increased risk of digestive system cancers, especially among Asian populations.

Peroxisome proliferator-activated receptor-γ 34C>G polymorphism and colorectal cancer risk: A meta-analysis

AIM: To investigate the association between peroxisome proliferator-activated receptor-γ (PPAR-γ) gene polymorphism 34 C>G and colorectal cancer (CRC), a meta-analysis review was performed in this report.

METHODS: A systematic literature search and selection of eligible relevant studies were carried out. Nine independent studies with a total number of 4533 cases and 6483 controls were included in the meta-analysis on the association between polymorphism 34 C>G and CRC.

RESULTS: There was no evidence for the association between PPAR-γ 34 C>G and CRC if all of the subjects in the nine studies were included. However, CG + GG showed a marginally significant difference from CC (OR = 0.84, 95% CI: 0.69-1.01, P = 0.07) in random-effect model. Stratified meta-analysis indicated that PPAR-γ 34 C>G was associated with colon cancer (OR = 0.8, 95% CI: 0.65-0.99, P = 0.04) in random-effect model, and the G allele decreased colon cancer risk. No significant association was observed between PPAR-γ 34 C>G and rectal cancer.

CONCLUSION: PPAR-γ 34 C>G is associated with colon cancer risk, but not associated with CRC and rectal cancer risk.

COX-2 polymorphisms and colorectal cancer risk: a strategy for chemoprevention

OBJECTIVE

COX-2, the inducible isoenzyme, was found to be overexpressed in approximately 85% of colorectal adenocarcinomas, contributing to key steps in tumor development. COX-2 polymorphisms that might modify the levels of protein expression would be anticipated to have a substantial influence on disease phenotype. Therefore, we sought to understand the role of three COX-2 polymorphisms (-1195A>G, -765G>C, and 8473T>C) in colorectal cancer (CRC) onset.

MATERIAL AND METHODS

We conducted a hospital-based case-control study involving 117 consecutively enrolled CRC patients and 256 healthy individuals without any clinical evidence of cancer. The COX-2 polymorphisms' genotypes were characterized by PCR-restriction fragment length polymorphism or real-time PCR techniques.

RESULTS

The -1195A>G polymorphism was associated with a 1.73-fold increased predisposition to CRC onset. In a stratified analysis, men and ever-smokers carrying -1195G allele (AG+GG) had an increased risk for CRC development (odds ratio: 2.58; 95% confidence intraval: 1.29-5.15 and odds ratio: 10.3; 95% confidence intraval: 3.37-31.2, respectively). More interestingly, men ever-smokers carrying -1195G allele appeared to have a nine-fold increased risk for CRC onset (95% CI: 2.94-27.6). No difference in the genotype's distribution was noticed between cases and controls for the remaining two polymorphisms.

CONCLUSION

The -1195A>G COX-2 polymorphism seems to modulate the genetic susceptibility for CRC onset, especially in men ever-smokers. This genetically based higher-risk group definition may help shift the balance between risk and benefits for the use of COX-2 inhibitors in chemoprevention that is currently hampered by the adverse gastrointestinal and cardiovascular side-effects.

Cyclooxygenase-2 polymorphisms, aspirin treatment, and risk for colorectal adenoma recurrence--data from a randomized clinical trial

Cyclooxygenase-2 (COX-2) catalyzes the rate-limiting step in the production of prostaglandins, potent mediators of inflammation. Chronic inflammation plays an important role in the development and progression of colorectal cancer. Aspirin inhibits COX-2 activity and lowers the risk for colorectal adenomas and cancer. We investigated whether common genetic variation in COX-2 influenced risk for colorectal adenoma recurrence among 979 participants in the Aspirin/Folate Polyp Prevention Study who were randomly assigned to placebo or aspirin and followed for 3 years for the occurrence of new adenomas. Of these participants, 44.2% developed at least one new adenoma during follow-up. Adjusted relative risks and 95% confidence intervals (95% CI) were calculated to test the association between genetic variation at six COX-2 single-nucleotide polymorphisms and adenoma occurrence and interaction with aspirin treatment. Two single-nucleotide polymorphisms were significantly associated with increased adenoma recurrence: for rs5277, homozygous carriers of the minor C allele had a 51% increased risk compared with GG homozygotes (relative risk, 1.51; 95% CI, 1.01-2.25), and for rs4648310, heterozygous carriers of the minor G allele had a 37% increased risk compared with AA homozygotes (relative risk, 1.37; 95% CI, 1.05-1.79). (There were no minor allele homozygotes.) In stratified analyses, there was suggestive evidence that rs4648319 modified the effect of aspirin. These results support the hypothesis that COX-2 plays a role in the etiology of colon cancer and may be a target for aspirin chemoprevention and warrant further investigation in other colorectal adenoma and cancer populations.

Genetic polymorphisms in the cyclooxygenase-1 and cyclooxygenase-2 genes and risk of colorectal adenoma

PURPOSE

Cyclooxygenase (COX) enzymes, COX1 and COX2, are key in converting arachidonic acid (AA) into prostaglandins that have been associated with colorectal carcinogenesis. The aim of our study was to investigate associations of polymorphisms in COX genes, alone and in interaction with exposures known to be related to inflammation and AA metabolism, with risk of colorectal adenomas.

MATERIALS AND METHODS

In a community-, colonoscopy-based case-control study with 162 incident, sporadic colorectal adenoma cases and 211 controls, we investigated associations of two promoter polymorphisms (-842 A > G in COX1 and -765 G > C in COX2) and two polymorphisms in the 3'-UTR of COX2 (8473 T > C and 9850 A > G) with risk of adenomas. Multiple logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals (CI) of colorectal adenoma after adjusting for potential confounders.

RESULTS

Overall, there was no evidence for an association between any of the four polymorphisms and colorectal adenomas. However, we found a statistically significant interaction between the COX2 8473 T > C polymorphism and nonsteroidal anti-inflammatory drug (NSAIDs) use (P (interaction) = 0.03): The greatest reduced risk was observed for individuals with the 8473 C variant allele who also regularly used NSAIDs (OR = 0.35, 95% CI 0.16-0.75).

CONCLUSION

These results suggest that the C allele of COX2 8473 T > C polymorphism may interact with NSAIDs to reduce risk for colorectal adenoma.

No association between cyclooxygenase-2 and uridine diphosphate glucuronosyltransferase 1A6 genetic polymorphisms and colon cancer risk

AIM: To investigate the association of variations in the cyclooxygenase-2 (COX2) and uridine diphosphate glucuronosyltransferase 1A6 (UGT1A6) genes and non-steroidal anti-inflammatory drugs (NSAIDs) use with risk of colon cancer.

METHODS: NSAIDs, which are known to reduce the risk of colon cancer, act directly on COX2 and reduce its activity. Epidemiological studies have associated variations in the COX2 gene with colon cancer risk, but others were unable to replicate this finding. Similarly, enzymes in the UGT1A6 gene have been demonstrated to modify the therapeutic effect of NSAIDs on colon adenomas. Polymorphisms in the UGT1A6 gene have been statistically shown to interact with NSAID intake to influence risk of developing colon adenomas, but not colon cancer. Here we examined the association of tagging single nucleotide polymorphisms (SNPs) in the COX2 and UGT1A6 genes, and their interaction with NSAID consumption, on risk of colon cancer in a population of 422 colon cancer cases and 481 population controls.

RESULTS: No SNP in either gene was individually statistically significantly associated with colon cancer, nor did they statistically significantly change the protective effect of NSAID consumption in our sample. Like others, we were unable to replicate the association of variants in the COX2 gene with colon cancer risk (P > 0.05), and we did not observe that these variants modify the protective effect of NSAIDs (P > 0.05). We were able to confirm the lack of association of variants in UGT1A6 with colon cancer risk, although further studies will have to be conducted to confirm the association of these variants with colon adenomas.

CONCLUSION: Our study does not support a role of COX2 and UGT1A6 genetic variations in the development of colon cancer.

Cyclooxygenase polymorphisms in gastric and colorectal carcinogenesis: are conclusive results available?

OBJECTIVE

Cyclooxygenases (COX) are important enzymes not only in the maintenance of mucosal integrity but also in pathological processes, namely in inflammation and tumor development in the gastrointestinal tract. Our goal was to understand whether there is a clear role for COX polymorphisms in gastric and colorectal carcinogenesis.

METHODS

A systematic review was conducted on observational studies assessing the involvement of COX polymorphisms at the onset of gastric or colorectal lesions, retrieved through a MEDLINE database search by May 2008. The dominant genetic model was assumed for each polymorphism and a random-effect model was used for pooling results.

RESULTS

Twenty-two studies were retrieved reporting a total of 26 COX polymorphisms (nine in COX1 and 17 in COX2 genes). Carriers of -1329A, -899C alleles, and *429TT genotype revealed increased risk for gastric cancer [odds ratio (OR)=1.83; 95% confidence interval (CI): 1.07-3.10, OR=2.02; 95% CI: 1.00-4.10 and OR=1.34; 95% CI: 1.06-1.71, respectively). For colorectal lesions, the -899G>C and -1329G>A polymorphisms also showed an increased risk for cancer (OR=1.35; 95% CI: 1.01-1.81 and OR=1.36; 95% CI: 1.11-1.66, respectively). Furthermore, C allele carriers of V102V single nucleotide polymorphisms presented a decreased risk for colorectal adenoma onset (OR=0.77; 95% CI: 0.58-1.03).

CONCLUSION

Although further studies, namely cohorts and/or adequately matched case-control studies, are required to unravel the impact of most COX polymorphisms, clearly there are evidences that support the involvement of -899G>C and -1329G>A COX2 polymorphisms in either gastric or colorectal carcinogenesis. These markers could be used to optimize management strategies (follow-up and/or chemoprevention).

Assembly of inflammation-related genes for pathway-focused genetic analysis

Recent identifications of associations between novel variants in inflammation-related genes and several common diseases emphasize the need for systematic evaluations of these genes in disease susceptibility. Considering that many genes are involved in the complex inflammation responses and many genetic variants in these genes have the potential to alter the functions and expression of these genes, we assembled a list of key inflammation-related genes to facilitate the identification of genetic associations of diseases with an inflammation-related etiology. We first reviewed various phases of inflammation responses, including the development of immune cells, sensing of danger, influx of cells to sites of insult, activation and functional responses of immune and non-immune cells, and resolution of the immune response. Assisted by the Ingenuity Pathway Analysis, we then identified 17 functional sub-pathways that are involved in one or multiple phases. This organization would greatly increase the chance of detecting gene-gene interactions by hierarchical clustering of genes with their functional closeness in a pathway. Finally, as an example application, we have developed tagging single nucleotide polymorphism (tSNP) arrays for populations of European and African descent to capture all the common variants of these key inflammation-related genes. Assays of these tSNPs have been designed and assembled into two Affymetrix ParAllele customized chips, one each for European (12,011 SNPs) and African (21,542 SNPs) populations. These tSNPs have greater coverage for these inflammation-related genes compared to the existing genome-wide arrays, particularly in the African population. These tSNP arrays can facilitate systematic evaluation of inflammation pathways in disease susceptibility. For additional applications, other genotyping platforms could also be employed. For existing genome-wide association data, this list of key inflammation-related genes and associated subpathways can facilitate comprehensive inflammation pathway- focused association analyses.

Review article: nutrition, obesity and colorectal cancer

BACKGROUND

The age-adjusted incidence of colorectal cancer is higher in prosperous industrialized countries than elsewhere. Dietary factors may account for 75% of sporadic colorectal cancer in the west, but the mechanisms remain obscure.

AIM

To review evidence for the effects of overweight and obesity, physical activity and specific dietary components on colorectal neoplasia.

METHODS

English language papers cited on MEDLINE, obtained using search terms related to colorectal cancer, physical activity and body mass and specific food components were reviewed.

RESULTS

There is evidence for adverse effects of overweight and obesity and protective effects of high physical activity against colon, but not for rectal cancer. These effects may reflect metabolic stress and chronic low-grade inflammation. There are also modest adverse effects of red and processed meat. There is evidence for protective effects of dietary fibre, but for fruits and vegetables the evidence remains weak and inconclusive. There is some evidence for protective effects of n-3 polyunsaturated fatty acids from fish, some micronutrients and possibly phytochemicals. The effects of many dietary constituents may depend upon genetic polymorphisms affecting a variety of genes.

CONCLUSION

Further research should focus particularly on the effects of insulin-resistance, impaired glucose tolerance and chronic low-grade inflammation on the colonic mucosa.