The MTHFR C677T and DeltaDNMT3B C-149T polymorphisms confer different risks for right- and left-sided colorectal cancer

Black raspberry extract shifted gut microbe diversity and their metabolic landscape in a human colonic model

Human gut microbiota is critical for human health, as their dysbiosis could lead to various diseases such as irritable bowel syndrome and obesity. Black raspberry (BRB) has been increasingly studied recently for its impact on gut microbiota as a rich source of phytochemicals (e.g., anthocyanin). To investigate the effect of BRB extract on the gut microbiota composition and their metabolism, an in-vitro human colonic model (HCM) was utilized to study the direct interaction between BRB and gut microbiome. Conditions (e.g., pH, temperature, anaerobic environment) in HCM were closely monitored and maintained to simulate the human intestinal system. Fresh fecal samples donated by three young healthy volunteers were used for gut microbiota inoculation in the HCM. 16S ribosomal DNA sequencing and liquid-chromatography mass spectrometry (LC/MS) based metabolomics were performed to study the impact of BRB on gut microbiota characteristics and their metabolism (fatty acids, polar metabolites, and phenolic compounds). Our data suggested that BRB intervention modulated gut microbiota at the genus level in different HCM sections mimicing ascending, transverse, and descending colons. Relative abundance of Enterococcus was commonly decreased in all colon sections, while modulations of other bacteria genera were mostly location-dependent. Meanwhile, significant changes in the metabolic profile of gut microbiota related to fatty acids, endogenous polar metabolites, and phenolic compounds were detected, in which arginine and proline metabolism, lysine degradation, and aminoacyl-tRNA biosynthesis were mostly regulated. Moreover, we identified several significant associations between altered microbial populations and changes in microbial metabolites. In summary, our study revealed the impact of BRB intervention on gut microbiota composition and metabolism change, which may exert physiological change to host metabolism and host health.

Temporal Trends of Sex Disparity in Incidence and Survival of Colorectal Cancer: Variations by Anatomical Site and Age at Diagnosis

Purpose

The incidence of colorectal cancer (CRC) varies by age, sex, and anatomical subsite. Few studies have examined the temporal trends of age-specific sex disparity in incidence and survival by age at diagnosis and anatomical site.

Patients and Methods

The study was performed on all incident cases of CRC, using data derived from the nationwide Swedish Cancer Register between 1960 and 2014, including right-sided colon cancer (RCC), left-sided colon cancer (LCC), and rectal cancer. Male-to-female age-standardized incidence rate ratio (IRR) and male-to-female five-year survival rate ratio (SRR) were calculated as the main indicators. Furthermore, we performed joinpoint regression analyses to estimate average annual percentage change.

Results

The overall male-to-female IRR was 1.05 for RCC, 1.31 for LCC, and 1.66 for rectal cancer. Male-to-female IRR increased steadily for RCC by an average of 0.4% per year until the mid-1990s and then decreased gradually by an average of 1.0% per year. LCC patients showed an increase of 0.6% per year since the mid-1970s. For rectal cancer, a non-significant random fluctuation was noted during the study period. The temporal trends of male-to-female IRR varied by age at diagnosis. The male-to-female SRR was 0.87 for RCC, 0.88 for LCC, and 0.86 for rectal cancer, which remained relatively stable during the study period.

Conclusion

Sex disparity of CRC is age-, period-, and anatomical subsite-dependent. Further studies are needed to investigate the underlying contributing factors.

Alcohol-Induced Epigenetic Changes in Cancer

Chronic, heavy alcohol consumption is associated with serious negative health effects, including the development of several cancer types. One of the pathways affected by alcohol toxicity is the one-carbon metabolism. The alcohol-induced impairment of this metabolic pathway results in epigenetic changes associated with cancer development. These epigenetic changes are induced by folate deficiency and by products of the ethanol metabolism. The changes induced by long-term heavy ethanol consumption result in elevations of homocysteine and S-adenosyl-homocysteine (SAH) and reductions in S-adenosylmethionine (SAM) and antioxidant glutathione (GSH) levels, leading to abnormal promoter gene hypermethylation, global hypomethylation, and metabolic insufficiency of antioxidant defense mechanisms. In addition, reactive oxygen species (ROS) generated during the ethanol metabolism induce alterations in DNA methylation patterns that play a critical role in cancer development. Specific epigenetic changes in esophageal, hepatic, and colorectal cancers have been detected in blood samples and proposed to be used clinically as epigenetic biomarkers for diagnosis and prognosis of these cancers. Also, genetic variants of genes involved in one-carbon metabolism and ethanol metabolism were found to modulate the relationship between alcohol-induced epigenetic changes and cancer risk. Furthermore, alcohol metabolism products have been associated with an increase in NADH levels, which lead to histone modifications and changes in gene expression that in turn influence cancer susceptibility. Chronic excessive use of alcohol also affects selected members of the family of microRNAs, and as miRNAs could act as epigenetic regulators, this may play an important role in carcinogenesis. In conclusion, targeting alcohol-induced epigenetic changes in several cancer types could make available clinical tools for the diagnosis, prognosis, and treatment of these cancers, with an important role in precision medicine.

Methylenetetrahydrofolate reductase C677T polymorphism and colorectal cancer susceptibility: a meta-analysis

The association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and colorectal cancer (CRC) susceptibility has been researched in numerous studies. However, the results of these studies were controversial. Therefore, the objective of this meta-analysis was to offer a more convincible conclusion about such association with more included studies. Eligible studies published till May 1, 2017 were searched from PubMed, Embase, Web of Science, and CNKI database about such association. Pooled odds ratios (ORs) together with 95% confidence intervals (CIs) were calculated to evaluate such association. And the Begg's funnel plot and Egger's test were applied to assess the publication bias. This meta-analysis contained 37049 cases and 52444 controls from 87 publications with 91 eligible case-control studies. Because of lack of data for a particular genotype in several studies, all the included studies were analysed barely in the dominant model. Originally, there was no association between MTHFR C677T polymorphism and CRC susceptibility (OR =0.99, 95% CI =0.94-1.05). After excluding 13 studies according to their heterogeneity and publication bias, rs1801133 polymorphism was found to reduce the risks of CRC significantly (OR =0.96, 95% CI =0.94-0.99). In the subgroup analysis of ethnicity, there was a significant association in Asians (OR =0.94, 95% CI =0.89-1.00). Furthermore, when stratified by the source of controls and genotyping methods, the positive results were observed in population-based control group (OR =0.97, 95% CI =0.93-1.00) and PCR-restriction fragment length polymorphism (PCR-RFLP) method (OR =0.95, 95% CI =0.91-0.99. The results of the meta-analysis suggested that MTHFR C677T polymorphism was associated with CRC susceptibility, especially in Asian population.

Meta-analysis Reveals No Association of DNMT3B -149 C>T Gene Polymorphism With Overall Cancer Risk

Background:

DNA methyltransferase-3B (DNMT3B) plays a key role in establishment and maintenance of genomic methylation patterns. Polymorphism in promoter region -149 C>T (C46359T) of DNMT3B gene may alter DNMT3B activity which leads to increased susceptibility to cancer. Inconsistent results regarding this have been reported in a number of studies.

Objective:

To carry out a meta-analysis of the studies reported to assess the precise relationship between the DNMT3B -149 C>T polymorphism and the overall cancer risk.

Method:

PubMed (MEDLINE) web database was searched for the studies concerning DNMT3B -149 C>T polymorphism and its association with cancer risk. The pooled odds ratios (ORs) along with 95% confidence intervals (95% CIs) were calculated for all the genetic models, from the selected case-control studies, by meta-analysis.

Results:

Overall eighteen studies containing 5583 cancer cases and 7618 controls were analyzed. No significant risk was observed overall for T allele carrier (T vs. C: p=0.303; OR=1.032, 95% CI=0.972-1.097), homozygous (TT vs. CC: p=0.336; OR=1.063, 95% CI=0.939–1.204), heterozygous (CT vs. CC: p=0.802; OR=1.022, 95% CI=0.860-1.216), dominant (TT vs. CC+CT: p=0.298; OR=1.101, 95% CI=0.919-1.319) and recessive (TT+CT vs. CC: p=0.656; OR=1.021, 95% CI=0.931-1.121) genetic models. Subgroup analysis of Asian and Caucasian populations also did not demonstrate any cancer risk in all the genetic models studied.

Conclusion:

Our meta-analysis proposes that the DNMT3B -149 C>T polymorphism may not be an independent predisposing factor for the risk of cancer. However, larger sample size and expression studies are required to confirm the observation.

DNA methyltransferase 3A promoter polymorphism is associated with the risk of human spontaneous abortion after assisted reproduction techniques and natural conception

PURPOSE

The aim of this study was to explore the association of the DNA-methyltransferase (DNMT)-3A and DNMT3B promoter polymorphisms with the risk of human spontaneous abortion after assisted reproduction techniques (ARTs) and natural conception.

METHODS

We collected tissues from women who underwent abortion procedures: (a) chorionic villus samples (CVS) and muscle samples (MS) from spontaneous abortions conceived by ART and natural cycle (study group), n = 152; and (b) CVS and MS from normal early pregnancy and second trimester (control group), n = 155. The single-nucleotide polymorphism (SNP) -448A > G in the DNMT3A promoter region and -149C/T polymorphism of DNMT3B were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and confirmed by sequencing.

RESULTS

The allele frequency of -448A among pregnancy loss group and control group was 34.2 % vs. 16.5 %, respectively. Compared with GG carriers, the DNMT3A -448AA homozygotes had an about 16-fold increased risk of spontaneous abortion [odds ratio (OR) = 16.130, 95 % confidence interval (CI), 3.665-70.984], and AG heterozygotes had an OR of 2.027 (95 % CI, 1.247-3.293). However, the distribution of -448A > G in individuals derived from ART pregnancies was not statistically significantly compared with those derived from spontaneous pregnancies (P = 0.661). For DNMT3B, we observed genotype frequencies of 100 % (TT) in the study group and the control group.

CONCLUSIONS

The DNMT3A -448A > G polymorphism may be a novel functional SNP and contribute to its genetic susceptibility to spontaneous abortion in Chinese women, and ART may not affect the distribution of -448A > G in pregnancy loss and normal pregnancy. The observed TT genotype of DMNT3B suggests that this is the predominant genotype of this population. The findings provide new insights into the etiology of human spontaneous abortion.

Differences in prognosis and molecular biological features between left- and right-sided colon cancer

Apart from differences in epidemiologic, pathologic and symptomatic features, the natural prognosis, therapeutic prognosis, as well as survival after relapse also show great differences between left- and right-sided colon cancer. Those differences in prognosis are noticed to be dependent on tumor stage and also thought to be due to the variant genetic background and molecular biological features. In this review, we summarize the differences in prognosis and molecular biological features between left- and right-sided colon cancer, and discuss the possible connections between clinical and molecular differences. Taking into account the impact that location and differentially expressed molecules may have on prognosis, clinicians could have a more accurate estimate on the prognosis of colon cancer patients.

MicroRNA in rectal cancer

In rectal cancer, one of the most common cancers worldwide, the proper staging of the disease determines the subsequent therapy. For those with locally advanced rectal cancer, a neoadjuvant chemoradiotherapy (CRT) is recommended before any surgery. However, response to CRT ranges from complete response (responders) to complete resistance (non-responders). To date we are not able to separate in advance the first group from the second, due to the absence of a valid biomarker. Therefore all patients receive the same therapy regardless of whether they reap benefits. On the other hand almost all patients receive a surgical resection after the CRT, although a watch-and-wait procedure or an endoscopic resection might be sufficient for those who responded well to the CRT. Being highly conserved regulators of gene expression, microRNAs (miRNAs) seem to be promising candidates for biomarkers. Many studies have been analyzing the miRNAs expressed in rectal cancer tissue to determine a specific miRNA profile for the ailment. Unfortunately, there is only a small overlap of identified miRNAs between different studies, posing the question as to whether different methods or differences in tissue storage may contribute to that fact or if the results simply are not reproducible, due to unknown factors with undetected influences on miRNA expression. Other studies sought to find miRNAs which correlate to clinical parameters (tumor grade, nodal stage, metastasis, survival) and therapy response. Although several miRNAs seem to have an impact on the response to CRT or might predict nodal stage, there is still only little overlap between different studies. We here aimed to summarize the current literature on rectal cancer and miRNA expression with respect to the different relevant clinical parameters.

A telephone survey of factors affecting willingness to participate in health research surveys

Background

In recent years, reduced participation has been encountered across all epidemiological study designs, both in terms of non-response as well as refusal. A low response rate may reduce the statistical power but, more importantly, results may not be generalizable to the wider community.

Methods

In a telephone survey of 1413 randomly selected members of the Australian general population and of 690 participants sourced from previous studies, we examined factors affecting people’s stated willingness to participate in health research.

Results

The majority of participants (61 %) expressed willingness to participate in health research in general but the percentage increased when provided with more specific information about the research. People were more willing if they have personal experience of the disease under study, and if the study was funded by government or charity rather than pharmaceutical companies.

Participants from previous studies, older people and women were the groups most willing to participate. Younger men preferred online surveys, older people a written questionnaire, and few participants in any age and sex groups preferred a telephone questionnaire.

Conclusion

Despite a trend toward reduced participation rates, most participants expressed their willingness to participate in health research. However, when seeking participants, researchers should be concrete and specific about the nature of the research they want to carry out. The preferred method of recommended contact varies with the demographic characteristics.

Puzzling role of genetic risk factors in human longevity: "risk alleles" as pro-longevity variants

Complex diseases are major contributors to human mortality in old age. Paradoxically, many genetic variants that have been associated with increased risks of such diseases are found in genomes of long-lived people, and do not seem to compromise longevity. Here we argue that trade-off-like and conditional effects of genes can play central role in this phenomenon and in determining longevity. Such effects may occur as result of: (i) antagonistic influence of gene on the development of different health disorders; (ii) change in the effect of gene on vulnerability to death with age (especially, from “bad” to “good”); (iii) gene–gene interaction; and (iv) gene–environment interaction, among other factors. A review of current knowledge provides many examples of genetic factors that may increase the risk of one disease but reduce chances of developing another serious health condition, or improve survival from it. Factors that may increase risk of a major disease but attenuate manifestation of physical senescence are also discussed. Overall, available evidence suggests that the influence of a genetic variant on longevity may be negative, neutral or positive, depending on a delicate balance of the detrimental and beneficial effects of such variant on multiple health and aging related traits. This balance may change with age, internal and external environments, and depend on genetic surrounding. We conclude that trade-off-like and conditional genetic effects are very common and may result in situations when a disease “risk allele” can also be a pro-longevity variant, depending on context. We emphasize importance of considering such effects in both aging research and disease prevention.

Systematic evaluation of cancer risk associated with DNMT3B polymorphisms

PURPOSE

The aim of our study is to provide a precise quantification for the association between DNA methyltransferase 3B (DNMT3B) variations (rs2424913 C/T, rs1569686 G/T, rs6087990 T/C and rs2424908 T/C) and the risk of cancer.

METHODS

We performed a systematic literature review and assessed the methodological quality of included case-control designed studies based on Newcastle-Ottawa Scale. Pooled odds ratios (ORs) and corresponding 95% confidence intervals (95% CIs) were calculated to assess the strengths of the associations.

RESULTS

We identified 34 studies for pooled analyses. Overall, the results demonstrated that rs2424913 polymorphism was significantly associated with negative cancer risk in the African population (CT vs TT: OR 0.10, 95% CI 0.02-0.63, P = 0.01; CT+CC vs TT: OR 0.14, 95% CI 0.03-0.76, P = 0.02), and the rs1569686 polymorphism was significantly associated with a subtly decreased cancer risk (GT vs TT: OR 0.80, 95% CI 0.72-0.90, P < 0.01; GT+GG vs TT: OR 0.84, 95% CI 0.76-0.94, P < 0.01), particularly in the Asian population (GT vs TT: OR 0.79, 95% CI 0.66-0.96, P < 0.01) and in colorectal cancer subgroup (G vs T: OR 0.69, 95% CI 0.54-0.88, P < 0.01). In addition, the rs6087990 polymorphism was associated with decreased risk in Asian population (T vs C: OR 0.77, 95% CI 0.62-0.96, P = 0.02). Similarly, the rs2424908 polymorphism was observed as a protective factor for cancer in the Asian population (CT+CC vs TT: OR 0.79, 95% CI 0.66-0.95, P = 0.01).

CONCLUSIONS

DNMT3B polymorphisms might be associated with decreased cancer risk especially in the Asian population and for colorectal cancer. Further multicentric studies are still needed to confirm the results.

A cross-sectional survey to investigate community understanding of medical research ethics committees

Study explanatory forms often state that an ethics committee has approved a research project. To determine whether the lay community understand the roles of ethics committees in research, we took a cross-sectional national sample from three sampling frames: the general population (n=1532); cohort study participants (n=397); and case-control study participants (n=151). About half (51.3%) of the participants had heard of ethics committees. Those who had were more likely to be those who had participated in previous surveys, older participants, those born in Australia and those with higher education. Almost all participants agreed that the roles of an ethics committee were to protect participants' privacy and ensure no harm came to study participants and most agreed that the committee's role was to ensure that the research was capable of providing answers. Case-control and cohort participants were more likely than the general population to consider that the role of an ethics committee was to design the research and obtain research funding. Overall, we found that about half of the population are aware of ethics committees and that most could correctly identify that ethics committees are there to protect the welfare and rights of research participants, although a substantial minority had some incorrect beliefs about the committees' roles. Increased education, particularly for migrants and older people, might improve understanding of the role of ethics committees in research.

Maternal risk for down syndrome and polymorphisms in the promoter region of the DNMT3B gene: a case-control study

BACKGROUND

Epigenetic changes leading to improper methylation of the pericentromeric region of chromosome 21 may contribute to the nondisjunction of this chromosome. Polymorphisms in the DNA Methyltransferase 3B (DNMT3B) gene, one of the crucial gene of the folate metabolism, affects the activity of the enzyme and increases the susceptibility of nondisjunction in mothers of Down syndrome children (MDS).

METHODS

Considering this hypothesis we investigated the association of single nucleotide polymorphisms in the promoter region of the DNMT3B gene (rs1569686 -579G>T; rs2424913 -149C>T) with a predisposition of mothers to deliver a Down syndrome (DS) child. The study was performed on DNA samples from 150 MDS and 172 control mothers. Transmission disequilibrium tests were performed on 103 DS trio families. Genotyping was done using a polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

With respect to the single nucleotide polymorphisms studied, no significant difference was observed in the genotypes and alleles frequency distributions between MDS and control mothers. The frequency of the DNMT3B-579G allele was, respectively, 0.34 in MDS and 0.33 in control mothers whereas the frequency of the DNMT3B-149C allele was respectively 0.31 in MDS and 0.26 in control mothers. No significant deviation in genotypic combinations as well as in transmission disequilibrium tests analysis was observed. However, a strong linkage disequilibrium was observed with significant differences in the distribution of G-T and G-C haplotypes among case and control mothers.

CONCLUSION

Although the above studied polymorphisms of DNMT3B may not be an independent risk factor it might be possible that certain allelic combinations (G-T) are. This finding suggests that DNMT3B might be a maternal risk factor for DS in our Indian cohort. Replication studies are required to confirm these findings.

Polymorphism of DNA methyltransferase 3B -149C/T and cancer risk: a meta-analysis

Published data on the association between DNA methyltransferase (DNMT) 3B -149C/T polymorphism and cancer risk remain inconclusive. To derive a more precise estimation for this association, we performed a meta-analysis of 5,903 cancer cases and 8,132 controls from 22 published case-control studies. We used odds ratios (ORs) with 95 % confidence intervals (CIs) to assess the strength of the association. Our meta-analysis suggested that DNMT3B -149C/T polymorphism was associated with the risk of head and neck cancer under heterozygote comparison (OR 0.73, 95 % CI 0.59-0.90) and dominant model (OR 1.75, 95 % CI 0.62-0.92), although no evidence of association between DNMT3B -149C/T polymorphism and cancer risk was observed as we compared in the pooled analyses (homozygote comparison: OR 0.96, 95 % CI 0.86-1.09; heterozygote comparison: OR 1.07, 95 % CI 0.86-0.32; dominant model: OR 1.03, 95 % CI 0.85-1.25; recessive model: OR 0.93, 95 % CI 0.8-1.08). More studies are needed to detect DNMT3B -149C/T polymorphism and its association with cancer in different ethnic populations incorporated with environment exposures in the susceptibility of different kinds of cancer.

Is right-sided colon cancer different to left-sided colorectal cancer? - a systematic review

Colorectal cancer (CRC) exhibits differences in incidence, pathogenesis, molecular pathways and outcome depending on the location of the tumor. This review focuses on the latest developments in epidemiological and scientific studies, which have enhanced our understanding on the underlying genetic and immunological differences between the proximal (right-sided) colon and the distal (left-sided) colorectum. The different ways in which environmental risk factors influence the pathogenesis of CRC depending on its location and the variations in surgical and oncological outcomes are also discussed in this review. In the current era of personalized medicine, we aim to reiterate the importance of tumor location in management of CRC and the implication on future clinical and scientific research.

The methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and tumor risk: evidence from 134 case-control studies

Methylenetetrahydrofolate reductase (MTHFR) is an important enzyme involved in folate metabolism, which is essential for DNA synthesis and methylation. Genetic variations in the MTHFR gene seem to contribute to a decreased activity of MTHFR, ultimately confer increased susceptibility to cancer. As the most extensively studied polymorphism, MTHFR C677T polymorphism was shown to contribute to cancer susceptibility but the results were inconsistent. The authors performed a meta-analysis including 134 studies (46,207 cases and 69,160 controls) to address the issue. Odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were used to assess the association. Overall, a significant elevated risk of cancer was associated with the MTHFR C677T polymorphism in T-allele versus C-allele comparison (OR = 1.06, 95% CI 1.02-1.11, P(heterogeneity) < 0.001), homozygote model (OR = 1.08, 95% CI 1.01-1.17, P(heterogeneity) < 0.001) and dominant model (OR = 1.05, 95% CI 1.00-1.10, P(heterogeneity) < 0.001). In the stratified analyses, significantly increased cancer risks were indicated among Asians in all genetic models except for heterozygote model. Further analysis revealed that C677T was significantly associated with an increased risk of esophageal and stomach cancer. This meta-analysis supports an association between the MTHFR C677T polymorphism and increased risk of esophageal and stomach cancer, especially among Asians. Additionally, more high-quality studies and that the covariates responsible for heterogeneity should be controlled to obtain a more conclusive response about the function of MTHFR C677T in cancer.

Focus on genetic and epigenetic events of colorectal cancer pathogenesis: implications for molecular diagnosis

Originally, colorectal cancer (CRC) tumorigenesis was understood as a multistep process that involved accumulation of tumor suppressor genes and oncogenes mutations, such as APC, TP53 and KRAS. However, this assumption proposed a relatively limited repertoire of genetic alterations. In the last decade, there have been major advances in knowledge of multiple molecular pathways involved in CRC pathogenesis, particularly regarding cytogenetic and epigenetic events. Microsatellite instability, chromosomal instability and CpG island methylator phenotype are the most analyzed cytogenetic changes, while DNA methylation, modifications in histone proteins and microRNAs (miRNAs) were analyzed in the field of epigenetic alterations. Therefore, CRC development results from interactions at many levels between genetic and epigenetic amendments. Furthermore, hereditary cancer syndrome and individual or environmental risk factors should not be ignored. The difficulties in this setting are addressed to understand the molecular basis of individual susceptibility to CRC and to determine the roles of genetic and epigenetic alterations, in order to yield more effective prevention strategies in CRC patients and directing their treatment. This review summarizes the most investigated biomolecular pathways involved in CRC pathogenesis, their role as biomarkers for early CRC diagnosis and their possible use to stratify susceptible patients into appropriate screening or surveillance programs.

Genetic polymorphism of DNA methyltransferase 3B 149 C>T and risk of colorectal cancer: a meta-analysis

Numerous studies have investigated the risk of colorectal cancer (CRC) associated with the polymorphism of DNA methyltransferase 3B (DNMT3B) 149 C>T, but results have been inconsistent. We performed this meta-analysis to drive a more precise estimation of the association between this polymorphism and risk of CRC. A comprehensive search was conducted to identify all case-control studies of the -149C>T polymorphism of DNMT3B and CRC risk. A total of seven eligible studies, including 2,666 cases and 4,022 controls, relating the DNMT3B polymorphism of -149C>T to the risk of CRC were identified. It suggested no significant associations between -149C>T polymorphism of DNMT3B gene and the risk of developing CRC in the recessive, dominant, and co-dominant models (for CC versus TT: OR = 0.90, 95% CI = 0.90-1.25, P heterogeneity = 0.37; for recessive model: OR = 0.54, 95% CI = 0.28-1.04, P heterogeneity = 0.00001; for dominant model: OR = 1.07, 95% CI = 0.93-1.23, P heterogeneity = 0.83; and for C allele versus T allele: OR = 0.70, 95% CI = 0.43-1.13, P heterogeneity = 0.00001). In the subgroup analysis, there is no significant associations were also found in European populations (for CC versus TT: OR = 1.09, 95% CI = 0.92-1.30, P heterogeneity = 0.88; for recessive model: OR = 1.00, 95% CI = 0.88-1.13, P heterogeneity = 0.14; for dominant model: OR = 1.50, 95% CI = 0.89-2.54, P heterogeneity = 0.00001; and for C allele versus T allele: OR = 0.70, 95% CI = 0.38-1.28, P heterogeneity = 0.00001). In conclusion, no significant association was found between the -149C>T polymorphisms in DNMT3B and CRC susceptibility.

Association of methylenetetrahydrofolate reductase C677T and A1298C polymorphisms with colorectal cancer risk: A meta-analysis

Colorectal cancer (CRC) is one of the most common types of cancer worldwide and a leading cause of cancer-related mortality. This meta-analysis was conducted to determine the effect of methylenetetrahydrofolate reductase (MTHFR) mutants on the risk of CRC. A literature search was conducted on PubMed, Medline and the China National Knowledge Infrastructure (CNKI) databases. Eligible studies were collected based on rigorous criteria of inclusion. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated by the fixed- or random-effects model. After all the studies were pooled, the OR of CRC for individuals carrying the MTHFR 677TT genotype, compared to the CC genotype, was 0.89 (95% CI: 0.82-0.97). When analyzed by ethnicity, Asians with the MTHFR 1298CC genotype exhibited a decreased risk of CRC (OR=0.69; 95% CI: 0.54-0.89). In a mixed population, a significantly reduced risk of CRC was observed among carriers of the 677TT (OR=0.86; 95% CI: 0.76-0.96) and the 1298CC (OR=0.82; 95% CI: 0.69-0.98) genotypes, compared to the wild-type homozygous genotype. In the subgroup of colon cancer, the OR of 677TT vs. CC+CT was 0.83 (95% CI: 0.72-0.96) and the OR of 1298CC vs. AA+AC was 0.81 (95% CI: 0.69-0.96). In the rectal cancer subgroup, the OR of 677TT vs. CC+CT was 0.86 (95% CI: 0.77-0.97). Therefore, this meta-analysis suggested that the MTHFR 677T and 1298C alleles were associated with a low risk of CRC.

The 46359CT polymorphism of DNMT3B is associated with the risk of cervical cancer

Abnormal methylation is related to cancer development. Since DNMT3B is an enzyme that modulates genomic methylation, we hypothesized that genetic variants of the promoter DNMT3B may be associated with an increased risk of developing cervical cancer. Our aim was to investigate the association between -579GT and 46359CT polymorphisms of DNMT3B and cervical cancer, high-grade squamous intraepithelial lesions (HSIL), and low-grade squamous intraepithelial lesions (LSIL). Samples from 200 healthy women and 130 women with squamous intraepithelial lesions (70 with cervical cancer, 30 with HSIL, and 30 with LSIL) were analyzed. Polymorphism genotyping was performed using PCR and restriction fragment length polymorphism. The -579GT polymorphism was not associated with cervical cancer, HSIL, or LSIL. The CT genotype of 46359CT polymorphism was significantly associated with cervical cancer risk (OR 8.75, CI 1.27-374.1), whereas the TT genotype was associated with a significantly decreased risk of HSIL (OR 0.66, CI 0.01-0.32) and LSIL (OR 0.11, CI 0.026-0.45). Our results suggest that genotyping the 46359CT polymorphism in DNMT3B may help identify women who are genetically susceptible to cervical cancer development. Additional studies with larger sample sizes are necessary to confirm our findings.

The 677C>T (rs1801133) polymorphism in the MTHFR gene contributes to colorectal cancer risk: a meta-analysis based on 71 research studies

Background

The 677C>T polymorphism of methylenetetrahydrofolate reductase (MTHFR) gene is considered to have a significant effect on colorectal cancer susceptibility, but the results are inconsistent. In order to investigate the association between the MTHFR 677C>T polymorphism and the risk of colorectal cancer, a meta-analysis was held based on 71 published studies.

Methods

Eligible studies were identified through searching the MEDLINE, EMBASE, PubMed, Web of Science, Chinese Biomedical Literature database (CBM) and CNKI database. Odds ratios (OR) and 95% confidence intervals (CIs) were used to assess the association. The statistical heterogeneity across studies was examined with x²-based Q-test. Begg's and Egger's test were also carried out to evaluate publication bias. Sensitive and subgroup analysis were also held in this meta-analysis.

Results

Overall, 71 publications including 31,572 cases and 44,066 controls were identified. The MTHFR 677 C>T variant genotypes are significantly associated with increased risk of colorectal cancer. In the stratified analysis by ethnicity, significantly increased risks were also found among Caucasians for CC vs TT (OR = 1.076; 95%CI =  1.008–1.150; I² = 52.3%), CT vs TT (OR = 1.102; 95%CI = 1.032–1.177; I² = 51.4%) and dominant model (OR = 1.086; 95%CI = 1.021–1.156; I² = 53.6%). Asians for CC vs TT (OR  = 1.226; 95%CI  = 1.116–1.346; I²  = 55.3%), CT vs TT (OR  = 1.180; 95%CI  = 1.079–1.291; I²  = 36.2%), recessive (OR  = 1.069; 95%CI  = 1.003-1.140; I²  = 30.9%) and dominant model (OR  = 1.198; 95%CI  = 1.101-1.303; I²  = 52.4%), and Mixed populations for CT vs TT (OR  = 1.142; 95%CI  = 1.005-1.296; I²  = 0.0%). However, no associations were found in Africans for all genetic models.

Conclusion

This meta-analysis suggests that the MTHFR 677C>T polymorphism increases the risk for developing colorectal cancer, while there is no association among Africans found in subgroup analysis by ethnicity.

A literature review of MTHFR (C677T and A1298C polymorphisms) and cancer risk

5,10-Methlenetetrahydrofolate reductase (MTHFR) is one of the most important enzymes for folate metabolism. This enzyme is mapped on chromosome 1, which is located at the end of the short arm (1p36.3). The C677T and A1298C are MTHFR polymorphisms that decrease in vitro MTHFR enzyme activity. Folate metabolism plays a key role in cell metabolism. These reactions are associated with purine-pyrimidine synthesis: DNA, RNA, and protein methylation. Polymorphism is also a factor in biodiversity, and be affected by ethnic heritage and geographic locale. In the case of unknown outcomes, not only should all geographical regions be investigated to ascertain biodiversity, but all populations as well to fully understand the variations in the effect. PUBMED was searched from January 2006 to December 2011 to develop an investigatory pursuit strategy. MTHFR, cancer, C677T, A1298C, and polymorphisms were key words used to focus the search. The literature review included all published relevant cancer types and MTHFR polymorphisms for that 5 years period. All selected polymorphisms data for cancer types was listed in tables for easy access and retrieval.

Folate Intake, MTHFR Polymorphisms, and the Risk of Colorectal Cancer: A Systematic Review and Meta-Analysis

Background. The objective was to determine whether relationships exist between the methylene-tetrahydrofolate reductase (MTHFR) polymorphisms and risk of colorectal cancer (CRC) and examine whether the risk is modified by level of folate intake. Methods. MEDLINE, Embase, and SCOPUS were searched to May 2012 using the terms "folic acid," "folate," "colorectal cancer," "methylenetetrahydrofolate reductase," "MTHFR." Observational studies were included which (1) assessed the risk of CRC for each polymorphism and/or (2) had defined levels of folate intake for each polymorphism and assessed the risk of CRC. Results. From 910 references, 67 studies met our criteria; hand searching yielded 10 studies. The summary risk estimate comparing the 677CT versus CC genotype was 1.02 (95% CI 0.95-1.10) and for 677TT versus CC was 0.88 (95% CI 0.80-0.96) both with heterogeneity. The summary risk estimates for A1298C polymorphisms suggested no reduced risk. The summary risk estimate for high versus low total folate for the 677CC genotype was 0.70 (95% CI 0.56-0.89) and the 677TT genotype 0.63 (95% CI 0.41-0.97). Conclusion. These results suggest that the 677TT genotype is associated with a reduced risk of developing CRC, under conditions of high total folate intake, and this associated risk remains reduced for both MTHFR 677 CC and TT genotypes.

Dietary and supplemental folate and the risk of left- and right-sided colorectal cancer

Epidemiological evidence suggests that folate may lower the risk of colorectal cancer (CRC) although studies have been inconsistent and some have indicated differences in the effects of naturally occurring dietary folate and the synthetic form of this vitamin, folic acid. Most studies to date have considered CRC as a single disease; however, cancers that develop on the left and right sides of the colorectum display important phenotypic differences, suggesting they may also have different risk factors. A population-based case-control study was conducted in Western Australia to examine the relationship between intake of both natural dietary folate and supplements containing folic acid and the risk of left- and right-sided CRC. Data were available for 850 cases (575 left-sided and 275 right-sided) and 958 controls. Odds ratios were calculated using multinomial logistic regression models. There was no association between natural dietary folate intake and risk of either left-or right-sided CRC. Supplement use similarly had no significant effect on right-sided CRC. However, long-term supplement users (4+ yr) were at lower risk of left-sided CRC than those who had not taken supplements (OR = 0.65, 95% CI, 0.50-0.86) and there was a significant trend in risk reduction as duration of use increased (P < 0.01).

The -149C>T polymorphism of DNMT3B is not associated with colorectal cancer risk: Evidence from a meta-analysis based on case-control studies

The aim of this study was to examine the association between the −149C>T polymorphism of DNA methyltransferase 3B (DNMT3B) and colorectal cancer (CRC) susceptibility. A comprehensive search was conducted to identify all case-control studies of the −149C>T polymorphism of DNMT3B and CRC risk. Statistical analysis was performed with the software program Stata (version 12.0) and Review Manager (version 5.0). A total of seven eligible studies, including 2,666 cases and 4,022 controls, associating the DNMT3B polymorphism of −149C>T with the risk of CRC were identified. These studies suggested no significant associations between the −149C>T polymorphism of the DNMT3B gene and the risk of developing CRC in the recessive, dominant and co-dominant models [for CC vs. TT: odds ratio (OR), 0.90; 95% confidence interval (CI), 0.90–1.25; P=0.37; for the recessive model: OR, 0.54, 95% CI, 0.28–1.04; P<0.00001; for the dominant model: OR, 1.07; 95% CI, 0.93–1.23; P=0.83 and C allele vs. T allele: OR, 0.70; 95% CI, 0.43–1.13; P<0.00001]. In the subgroup analysis, no significant associations were found in the European populations (for CC vs. TT: OR, 1.09; 95% CI, 0.92–1.30; P=0.88; for the recessive model: OR, 1.00; 95% CI, 0.88–1.13; P=0.14; for the dominant model: OR, 1.50; 95% CI, 0.89–2.54; P<0.00001 and C allele vs. T allele: OR, 0.70; 95% CI, 0.38–1.28; P<0.00001). No significant association was found between the −149C>T polymorphism in DNMT3B and CRC susceptibility.

MTHFR C677T polymorphism contributes to colorectal cancer susceptibility: evidence from 61 case-control studies

Methylenetetrahydrofolate reductase (MTHFR) is believed to be involved in folate metabolism which plays a critical role in carcinogenesis. To date, many case-control studies have investigated the association between MTHFR C677T polymorphism and colorectal cancer risk. However, the results were inconsistent. In order to derive a more precise estimation of the association, we conducted this meta-analysis. This meta-analysis recruited 61 published studies which were selected by a search of PubMed up to 31st September 2011, including 16,111 colorectal cancer cases and 23,192 controls. We used crude odds ratios (ORs) with 95 % confidence intervals (CIs) to assess the association between MTHFR C677T polymorphism and colorectal cancer susceptibility. Our results showed that MTHFR C667T polymorphism contributed to the decreased colorectal cancer risk in overall population (for TT vs. CC: OR = 0.89, 95 % CI = 0.82-0.97; for TT vs. CT/CC: OR = 0.88, 95 % CI = 0.83-0.92). In subgroup analysis by ethnicity, the results also indicated a correlation between the T allele of MTHFR C667T and the colorectal cancer risk in Asian population (for TT vs. CC: OR = 0.82, 95 % CI = 0.69-0.97; for TT vs. CT/CC: OR = 0.81, 95 % CI = 0.74-0.90). Additionally, the correlation was also observed in male subgroup in sub-analysis by gender (for TT vs. CC: OR = 0.82, 95 % CI = 0.71-0.93; for TT vs. CT/CC: OR = 0.81, 95 % CI = 0.71-0.92). In summary, our meta-analysis strongly indicated the MTHFR C667T polymorphism was associated with a reduced risk of CRC.

DNMT3B polymorphisms and cancer risk: a meta analysis of 24 case-control studies

The association between polymorphism of DNA methyltransferases 3B and cancer risk has been widely studied recently, and no consensus conclusion is available up to now. We perform a comprehensive search using the databases of Medline, ISI Web of Knowledge and Embase. The odds ratio (OR) and its 95% confidence interval (95% CI) are used to investigate the strength of the association. A total of 24 case-control studies with 15,647 individuals are included in this meta-analysis. For -149C > T (17 studies, 5229 cases and 6910 controls), no evidence indicate that individuals carrying the variant genotypes (CC + CT), relative to those carrying the wild homozygote TT genotype, have an increased risk of cancer (OR = 1.03; 95% CI = 0.84-1.26; P = 0.76). Similarly, no cancer risk is found in the subgroup analyses. For -579G > T (11 studies, 3513 cases and 3714 controls), significantly decreased risks of cancer are observed, and the ORs (95% CI) are 0.70 (0.56-0.87) for GT versus TT, 0.70 (0.57-0.85) for GG + GT versus TT and 0.76 (0.63-0.93) for G-allele versus T-allele, respectively. Subgroup analyses stratified by ethnicity and types of cancer are also performed, and results indicated that -579G > C polymorphism is associated with risk of cancer in Asians [0.68 (0.53-0.87) for GT vs. TT] but not in Europeans [0.82 (0.63-1.07) for GT vs. TT]. We also observe that the -579G is associated with decreased risk of colorectal cancer [0.49(0.38-0.62) for GT vs. TT]. More studies with larger sample size were needed to provide more precise evidence.

Folate and choline metabolism gene variants in relation to ovarian cancer risk in the Polish population

Data indicates that genetic factors alone do not account for ovarian tumorigenesis, suggesting that epigenetic status additionally affects this process. Therefore, we assessed the possible contribution of polymorphic variants of genes that may affect DNA methylation to the risk of ovarian cancer incidence in the Polish population. Using PCR-RFLP and HRM analyses, we studied the distribution of BHMT (rs3733890), MTHFD1 (rs2236225), MTHFR (rs1801133), MTR (rs1805087), MTRR (rs1801394) and TCN2 (rs1801198) genotypes and alleles in patients with ovarian cancer (n = 136) and controls (n = 160). Moreover, using DNA and methylation-specific PCR (MSP) we also determined the methylation of the Cadherin 13 (CDH13) promoter in cancerous tissue from these patients. We did not observe a significant association between all studied gene variants and the incidence of ovarian cancer. The lowest P (trend) = 0.1226 was observed for the MTHFR Ala222Val polymorphism. Moreover, the lowest P = 0.0772 was found in the comparison of MTHFR Ala/Ala versus Val/Val and Val/Ala genotypes in patients and control groups. The multifactor dimensionality reduction analysis also did not indicate a significant interactive genetic effect on ovarian cancer incidence for all analyzed SNPs. However, we observed frequent methylation of the CDH13 promoter in approximately 21% (29/136) patients with ovarian carcinomas. Our results might suggest that the selected polymorphic gene variants may not contribute to ovarian cancer incidence.

Fruit and vegetable consumption and the risk of proximal colon, distal colon, and rectal cancers in a case-control study in Western Australia

BACKGROUND

Fruits and vegetables (F/V) have been examined extensively in nutrition research in relation to colorectal cancer (CRC). However, their protective effect is subject to debate, possibly because of different effects on different subsites of the large bowel.

OBJECTIVE

To determine whether any association between F/V consumption and risk of CRC differed by subsite of the bowel (proximal colon, distal colon, and rectum).

DESIGN

The Western Australian Bowel Health Study is a population-based, case-control study conducted between June 2005 and August 2007. Complete food frequency questionnaire data were analysed from 834 CRC cases and 939 controls. Logistic regression analysis was used to estimate the effects of quartiles of F/V intake on risk of CRC at different subsites. Odds ratios (OR) and 95% confidence intervals (CI) were calculated for CRC overall and for the three separate subsites.

RESULTS

Risk of proximal colon cancer and rectal cancer was not associated with intakes of total F/V, total vegetable, or total fruit. Brassica vegetable intake was inversely related with proximal colon cancer (Q4 vs Q1 OR 0.62; 95% CI 0.41 to 0.93). For distal colon cancer, significant negative trends were seen for total F/V, and total vegetable intake. Distal colon cancer risk was significantly decreased for intake of dark yellow vegetables (Q4 vs Q1 OR 0.61; 95% CI 0.41 to 0.92) and apples (Q4 vs Q1 OR 0.51; 95% CI 0.34 to 0.77). An increased risk for CRC was found to be associated with intake of fruit juice (Q4 vs Q1 OR 1.74; 95% CI 1.24 to 2.45).

CONCLUSIONS

Our results suggest that different F/V may confer different risks for cancer of the proximal colon, distal colon, or rectum. Future studies might consider taking into account the location of the tumor when examining the relation between F/V consumption and risk of CRC.

Long-term sedentary work and the risk of subsite-specific colorectal cancer

Research suggests that sedentary behavior may increase the risk of some chronic diseases. The aims of the study were to examine whether sedentary work is associated with colorectal cancer and to determine whether the association differs by subsite. A total of 918 cases and 1,021 controls participated in a population-based case-control study of colorectal cancer in Western Australia in 2005-2007. Data were collected on lifestyle, physical activity, and lifetime job history. The estimated effects of sedentary work on the risk of cancers of the proximal colon, distal colon, and rectum were analyzed by using multinomial logistic regression. Compared with participants who did not spend any time in sedentary work, participants who spent 10 or more years in sedentary work had almost twice the risk of distal colon cancer (adjusted odds ratio = 1.94, 95% confidence interval: 1.28, 2.93) and a 44% increased risk of rectal cancer (adjusted odds ratio = 1.44, 95% confidence interval: 0.96, 2.18). This association was independent of recreational physical activity and was seen even among the most recreationally active participants. Sedentary work was not associated with the risk of proximal colon cancer. These results suggest that long-term sedentary work may increase the risk of distal colon cancer and rectal cancer.

Meat consumption and cooking practices and the risk of colorectal cancer

BACKGROUND/OBJECTIVES

The association between meat consumption and the risk of colorectal cancer (CRC) has been controversial. One of the difficulties in determining this association has been measurement of different attributes of meat consumption, including cooking methods and level of doneness.

SUBJECTS/METHODS

We investigated the association between meat consumption and cooking practices and the risk of CRC in a population-based case-control study in the Western Australian Bowel Health Study. From July 2005 to February 2007, 567 incident CRC cases and 713 controls, who were frequency matched to cases for age- and sex, completed questionnaires on lifestyle and meat consumption. Estimated odds ratios (ORs) comparing meat consumption quartile groups were obtained from multivariate logistic regression models.

RESULTS

The amount of red baked meat consumed had a statistically significant inverse trend of association with CRC (Q4 OR=0.73 95% confidence interval 0.53-1.01). When frequency was multiplied by serving size and by doneness, the association remained protective but was no longer statistically significant. The protective trends for red pan-fried meat were also borderline statistically significant. There were no other statistically significant or meaningful associations with any of the types of meat cooked by any method and the risk of CRC.

CONCLUSIONS

Our data do not support the hypothesis that meat consumption is a risk factor for CRC.

Genetics, cytogenetics, and epigenetics of colorectal cancer

Most of the colorectal cancer (CRC) cases are sporadic, only 25% of the patients have a family history of the disease, and major genes causing syndromes predisposing to CRC only account for 5-6% of the total cases. The following subtypes can be recognized: MIN (microsatellite instability), CIN (chromosomal instability), and CIMP (CpG island methylator phenotype). CIN occurs in 80-85% of CRC. Chromosomal instability proceeds through two major mechanisms, missegregation that results in aneuploidy through the gain or loss of whole chromosomes, and unbalanced structural rearrangements that lead to the loss and/or gain of chromosomal regions. The loss of heterozygosity that occur in the first phases of the CRC cancerogenesis (in particular for the genes on 18q) as well as the alteration of methylation pattern of multiple key genes can drive the development of colorectal cancer by facilitating the acquisition of multiple tumor-associated mutations and the instability phenotype.

Prognostic significance of CDKN2A (p16) promoter methylation and loss of expression in 902 colorectal cancers: Cohort study and literature review

A cyclin-dependent kinase inhibitor CDKN2A (p16/Ink4a) is a tumor suppressor and upregulated in cellular senescence. CDKN2A promoter methylation and gene silencing are associated with the CpG island methylator phenotype (CIMP) in colon cancer. However, prognostic significance of CDKN2A methylation or loss of CDKN2A (p16) expression independent of CIMP status remains uncertain. Using a database of 902 colorectal cancers in 2 independent cohort studies (the Nurses' Health Study and the Health Professionals Follow-up Study), we quantified CDKN2A promoter methylation and detected hypermethylation in 269 tumors (30%). By immunohistochemistry, we detected loss of CDKN2A (p16) expression in 25% (200/804) of tumors. We analyzed for LINE-1 hypomethylation and hypermethylation at 7 CIMP-specific CpG islands (CACNA1G, CRABP1, IGF2, MLH1, NEUROG1, RUNX3 and SOCS1); microsatellite instability (MSI); KRAS, BRAF and PIK3CA mutations; and expression of TP53 (p53), CTNNB1 (β-catenin), CDKN1A (p21), CDKN1B (p27), CCND1 (cyclin D1), FASN (fatty acid synthase) and PTGS2 (cyclooxygenase-2). CDKN2A promoter methylation and loss of CDKN2A (p16) were associated with shorter overall survival in univariate Cox regression analysis [hazard ratio (HR): 1.36, 95% CI: 1.10-1.66, p = 0.0036 for CDKN2A methylation; HR: 1.30, 95% CI: 1.03-1.63, p = 0.026 for CDKN2A (p16) loss] but not in multivariate analysis that adjusted for clinical and tumor variables, including CIMP, MSI and LINE-1 methylation. Neither CDKN2A promoter methylation nor loss of CDKN2A (p16) was associated with colorectal cancer-specific mortality in uni- or multivariate analysis. Despite its well-established role in carcinogenesis, CDKN2A (p16) promoter methylation or loss of expression in colorectal cancer is not independently associated with patient prognosis.

Nutrients in folate-mediated, one-carbon metabolism and the risk of rectal tumors in men and women

In an investigation of rectal tumors characterized by CpG island methylator phenotype (CIMP), KRAS2 mutation, and TP53 mutation, we examined associations with dietary and supplemental folate, riboflavin, vitamins B(6) and B(12), and methionine, nutrients involved in folate-mediated 1-carbon metabolism. We also examined folate intake and common MTHFR polymorphisms in relation to CIMP. Data from a population-based study of 951 cases (750 with tumor markers) and 1,205 controls were evaluated using multiple logistic regression models and generalized estimating equations. Reduced risk of methylated tumors was suggested in women with the upper tertile of folate intake (≥0.42 mg/day) vs. the lower tertile: OR = 0.6, 95%CI = 0.3-1.2. In men, a significant 3-fold increased risk of CIMP+ tumor was observed for the upper tertile of folate (≥0.75 mg/day) vs. the lower tertile (<0.44 mg/day): OR = 3.2, 95%CI = 1.5-6.7. These men consumed a greater proportion of folic acid fortified foods relative to natural, primarily plant-based sources (52% vs. 48%) than women with CIMP+ tumors (22% vs. 78%). MTHFR 1298A>C influenced folate in male CIMP+ risk (P interaction < 0.01). Our findings suggest folate supplementation effects may differ between genders, perhaps due to variation in MTHFR and/or endogenous/exogenous hormones, and may be important in the initiation and progression of methylated rectal tumors in men.

MicroRNAs and colon and rectal cancer: differential expression by tumor location and subtype

MicroRNAs are thought to have an impact on cell proliferation, apoptosis, stress responses, maintenance of stem cell potency, and metabolism and are, therefore, important in the carcinogenic process. In this study, we examined 40 colon tumors, 30 rectal tumors, and 30 normal tissue samples (10 proximal colon, 10 distal colon, and 10 rectal paired with cancer cases) to examine miRNA expression profiles in colon and rectal tumors. MiRNA expression levels were adjusted for multiple comparisons; tumor tissue was compared with noncancerous tissue from the same site. A comparison of normal tissue showed 287 unique miRNAs that were significantly differentially expressed at the 1.5-fold level and 73 with over a two-fold difference in expression between colon and rectal tissue. Examination of miRNAs that were significantly differentially expressed at the 1.5-fold level by tumor phenotype showed 143 unique miRNAs differentially expression for microsatellite instability positive (MSI+) colon tumors; 129 unique miRNAs differentially expressed for CpG Island Methylator Phenotype positive (CIMP+) colon tumors; 135 miRNAs were differentially expressed for KRAS2-mutated colon tumors, and 139 miRNAs were differentially expressed for TP53-mutated colon tumors. Similar numbers of differentially expressed miRNAs were observed for rectal tumors, although the miRNAs differentially expressed differed. There were 129 unique miRNAs for CIMP+, 143 unique miRNAs for KRAS2-mutated, and 136 unique miRNAs for TP53-mutated rectal tumors. These results suggest the importance of miRNAs in colorectal cancer and the need for studies that can confirm these results and provide insight into the diet, lifestyle, and genetic factors that influence miRNA expression.

MicroRNAs and colon and rectal cancer: differential expression by tumor location and subtype

MicroRNAs are thought to have an impact on cell proliferation, apoptosis, stress responses, maintenance of stem cell potency, and metabolism and are, therefore, important in the carcinogenic process. In this study, we examined 40 colon tumors, 30 rectal tumors, and 30 normal tissue samples (10 proximal colon, 10 distal colon, and 10 rectal paired with cancer cases) to examine miRNA expression profiles in colon and rectal tumors. MiRNA expression levels were adjusted for multiple comparisons; tumor tissue was compared with noncancerous tissue from the same site. A comparison of normal tissue showed 287 unique miRNAs that were significantly differentially expressed at the 1.5-fold level and 73 with over a two-fold difference in expression between colon and rectal tissue. Examination of miRNAs that were significantly differentially expressed at the 1.5-fold level by tumor phenotype showed 143 unique miRNAs differentially expression for microsatellite instability positive (MSI+) colon tumors; 129 unique miRNAs differentially expressed for CpG Island Methylator Phenotype positive (CIMP+) colon tumors; 135 miRNAs were differentially expressed for KRAS2-mutated colon tumors, and 139 miRNAs were differentially expressed for TP53-mutated colon tumors. Similar numbers of differentially expressed miRNAs were observed for rectal tumors, although the miRNAs differentially expressed differed. There were 129 unique miRNAs for CIMP+, 143 unique miRNAs for KRAS2-mutated, and 136 unique miRNAs for TP53-mutated rectal tumors. These results suggest the importance of miRNAs in colorectal cancer and the need for studies that can confirm these results and provide insight into the diet, lifestyle, and genetic factors that influence miRNA expression.

SHMT1 1420 and MTHFR 677 variants are associated with rectal but not colon cancer

Background

Association between rectal or colon cancer risk and serine hydroxymethyltransferase 1 (SHMT1) C1420T or methylenetetrahydrofolate reductase (MTHFR) C677T polymorphisms was assessed. The serum total homocysteine (HCY), marker of folate metabolism was also investigated.

Methods

The SHMT1 and MTHFR genotypes were determined by real-time PCR and PCR-RFLP, respectively in 476 patients with rectal, 479 patients with colon cancer and in 461 and 478, respective controls matched for age and sex. Homocysteine levels were determined by HPLC kit. The association between polymorphisms and cancer risk was evaluated by logistic regression analysis adjusted for age, sex and body mass index. The population stratification bias was also estimated.

Results

There was no association of genotypes or diplotypes with colon cancer. The rectal cancer risk was significantly lower for SHMT1 TT (OR = 0.57, 95% confidence interval (CI) 0.36-0.89) and higher for MTHFR CT genotypes (OR = 1.4, 95%CI 1.06-1.84). A gene-dosage effect was observed for SHMT1 with progressively decreasing risk with increasing number of T allele (p = 0.014). The stratified analysis according to age and sex revealed that the association is mainly present in the younger (< 60 years) or male subgroup. As expected from genotype analysis, the SHMT1 T allele/MTHFR CC diplotype was associated with reduced rectal cancer risk (OR 0.56, 95%CI 0.42-0.77 vs all other diplotypes together). The above results are unlikely to suffer from population stratification bias. In controls HCY was influenced by SHMT1 polymorphism, while in patients it was affected only by Dukes' stage. In patients with Dukes' stage C or D HCY can be considered as a tumor marker only in case of SHMT1 1420CC genotypes.

Conclusions

A protective effect of SHMT1 1420T allele or SHMT1 1420 T allele/MTHFR 677 CC diplotype against rectal but not colon cancer risk was demonstrated. The presence of SHMT1 1420 T allele significantly increases the HCY levels in controls but not in patients. Homocysteine could be considered as a tumor marker in SHMT1 1420 wild-type (CC) CRC patients in Dukes' stage C and D. Further studies need to clarify why SHMT1 and MTHFR polymorphisms are associated only with rectal and not colon cancer risk.

Polymorphisms in methyl-group metabolism genes and risk of sporadic colorectal cancer with relation to the CpG island methylator phenotype

BACKGROUND

The CpG island methylator phenotype (CIMP), together with extensive promoter methylation, is regarded as one of the mechanisms involved in colorectal carcinogenesis. The mechanisms underlying CIMP in sporadic colorectal cancer are poorly understood. Genes involved in methyl-group metabolism are likely to affect DNA methylation and thereby influence an individual's risk of CIMP. The aim of the present study was to evaluate whether polymorphisms in the genes encoding methyl-group metabolism pathway predispose to CIMP+ and/or CIMP- CRC.

METHODS

We examined the potential association between the polymorphisms of MTHFR 677C>T, TS 5'UTR 2R/3R, TS 3'UTR 1494del6, DeltaDNMT3B -149C>T and DNMT3B -283T>C in a group of 46 CIMP+ CRC cases, 140 CIMP- CRC cases and 140 healthy controls. The CIMP status of the CRC cases was determined by MS-PCR in tumor tissue by a panel of five markers (CACNA1G, IGF2, NEUROG1, RUNX3 and SOCS1), which was also followed by analyzing hMLH1 methylation and BRAF V600E mutation.

RESULTS

The variant allele homozygote genotype for the DeltaDNMT3B -283T>C polymorphism was associated with a decreased risk for CIMP+ CRC (OR: 0.31, 95%CI: 0.09-0.73, p=0.009). Individuals with TS 3R/3R had an increased risk of CIMP- CRC (OR: 2.21, 95%CI: 1.23-4.91, p=0.01). Moreover, the carriers of 3R allele had an increased risk of CIMP- CRC (OR: 1.45, 95%CI: 1.10-2.13, p=0.01).

CONCLUSION

This study provides support to the hypothesis that methyl-group metabolism plays a role in the etiology of both CIMP+ and CIMP- colorectal cancers but has a different impact on a distinct molecular subgroups of colorectal cancer.

CDK8 expression in 470 colorectal cancers in relation to beta-catenin activation, other molecular alterations and patient survival

Alterations in the Wnt/beta-catenin pathway define a key event in the pathogenesis of colon cancer. We have recently shown that CDK8, the gene encoding a cyclin-dependent kinase (CDK) component of the Mediator complex, acts as a colon cancer oncogene that is necessary for beta-catenin activity. Here, we tested the hypothesis that colorectal cancers with CDK8 expression have distinct clinical, prognostic and molecular attributes. Among 470 colorectal cancers identified in 2 prospective cohort studies, CDK8 expression was detected in 329 (70%) tumors by immunohistochemistry. Cox proportional hazards model and backward stepwise elimination were used to compute hazard ratio (HR) of deaths according to CDK8 status, initially adjusted for various patient and molecular features, including beta-catenin, p53, p21, p27 (CDK inhibitors), cyclin D1, fatty acid synthase (FASN), cyclooxygenase-2 (COX-2), microsatellite instability (MSI), CpG island methylator phenotype (CIMP), LINE-1 methylation, and mutations in KRAS, BRAF and PIK3CA. CDK8 expression in colorectal cancer was independently associated with beta-catenin activation (p = 0.0002), female gender (p < 0.0001) and FASN overexpression (p = 0.0003). Among colon cancer patients, CDK8 expression significantly increased colon cancer-specific mortality in both univariate analysis [HR 1.70; 95% confidence interval (CI), 1.03-2.83; p = 0.039] and multivariate analysis (adjusted HR 2.05; 95% CI, 1.18-3.56; p = 0.011) that was adjusted for potential confounders including beta-catenin, COX-2, FASN, LINE-1 hypomethylation, CIMP and MSI. CDK8 expression was unrelated with clinical outcome among rectal cancer patients. These data support a potential link between CDK8 and beta-catenin, and suggest that CDK8 may identify a subset of colon cancer patients with a poor prognosis.

Genetic variability in the MTHFR gene and colorectal cancer risk using the colorectal cancer family registry

BACKGROUND

The MTHFR C677T TT genotype is associated with a 15% to 18% reduction in colorectal cancer risk, but it is not clear if other variants of the gene are associated with colorectal cancer risk.

METHODS

We used a tagSNP approach to comprehensively evaluate associations between variation in the MTHFR gene and colorectal cancer risk using a large family-based case-control study of 1,750 population-based and 245 clinic-based families from the Colon Cancer Family Registry. We assessed 22 TagSNPs, selected based on pairwise r(2) >95%, using the Haploview Tagger and genotyped the TagSNPs on the Illumina GoldenGate or Sequenom platforms. The association between single nucleotide polymorphisms and colorectal cancer was assessed using log-additive, codominant, and recessive models.

RESULTS

From studying the population-based families, the C677T (rs1801133) and A1298C (rs1801131) polymorphisms were associated with a decreased colorectal cancer risk overall [odds ratio (OR), 0.81; 95% confidence interval (95% CI), 0.63-1.04; and OR, 0.82; 95% CI, 0.64-1.07, respectively]. The 677 TT genotype was associated with a decreased risk of microsatellite-stable/microsatellite-low tumors (OR, 0.69; 95% CI, 0.49-0.97) and an increased risk of microsatellite-high tumors (OR, 2.22; 95% CI, 0.91-5.43; P(interaction) = 0.01), as well as an increased risk of proximal cancers and a decreased risk of distal and rectal cancers (P(interaction) = 0.02). No other single nucleotide polymorphism was associated with risk overall or within subgroups.

CONCLUSION

The 677 TT and 1298 CC genotypes may each be associated with a decrease in colorectal cancer risk. We observed little evidence of additional genetic variability in the MTHFR gene relevant to colorectal cancer risk.