Proximal and distal colorectal cancers show distinct gene-specific methylation profiles and clinical and molecular characteristics

Recent progress of targeted nanocarriers in diagnostic, therapeutic, and theranostic applications in colorectal cancer

Cancer at the lower end of the digestive tract, colorectal cancer (CRC), starts with asymptomatic polyps, which can be diagnosed as cancer at a later stage. It is the fourth leading cause of malignancy-associated mortality worldwide. Despite progress in conventional treatment strategies, the possibility to overcome the mortality and morbidity issues with the enhancement of the lifespan of CRC patients is limited. With the advent of nanocarrier-based drug delivery systems, a promising revolution has been made in diagnosis, treatment, and theranostic purposes for cancer management. Herein, we reviewed the progress of miniaturized nanocarriers, such as liposomes, niosomes, solid lipid nanoparticles, micelles, and polymeric nanoparticles, employed in passive and active targeting and their role in theranostic applications in CRC. With this novel scope, the diagnosis and treatment of CRC have proceeded to the forefront of innovation, where specific characteristics of the nanocarriers, such as processability, flexibility in developing precise architecture, improved circulation, site-specific delivery, and rapid response, facilitate the management of cancer patients. Furthermore, surface-engineered technologies for the nanocarriers could involve receptor-mediated deliveries towards the overexpressed receptors on the CRC microenvironment. Moreover, the potential of clinical translation of these targeted miniaturized formulations as well as the possible limitations and barriers that could impact this translation into clinical practice were highlighted. The advancement of these newest developments in clinical research and progress into the commercialization stage gives hope for a better tomorrow.

SPARCL1 exhibits different expressions in left- and right-sided colon cancer and is downregulated via DNA methylation

Aim: The authors previously found that SPARCL1 functions to suppress colorectal cancer metastasis. Here, the epigenetic mechanism of SPARCL1 regulation and its relationship with clinicopathological features in colon cancer were investigated. Materials & methods: SPARCL1 expression was evaluated by immunohistochemistry staining in a tissue array containing 271 left-sided colon cancer samples and 257 right-sided colon cancer samples. In vivo and in vitro DNA methylation states were measured by biochemical sulfide potential assay. The transcription and DNA methylation states in cells were altered by siRNA or decitabine treatment, respectively. Cellular motility properties were compared through transwell assay. Results & conclusion: SPARCL1, mediated by its DNA methylation, may arrest colorectal carcinoma motility. Furthermore, SPARCL1 expression is higher and may have a specific prognostic value in left-sided colon cancer.

Epigenetic Alterations Upstream and Downstream of p53 Signaling in Colorectal Carcinoma

Colorectal cancer (CRC) belongs to the most common tumor types, and half of all CRC harbor missense mutations in the TP53 tumor suppressor gene. In addition to genetically caused loss of function of p53, epigenetic alterations (DNA methylation, histone modifications, micro-RNAs) contribute to CRC development. In this review, we focused on epigenetic alterations related to the entire p53 signaling pathway upstream and downstream of p53. Methylation of genes which activate p53 function has been reported, and methylation of APC and MGMT was associated with increased mutation rates of TP53. The micro-RNA 34a activates TP53 and was methylated in CRC. Proteins that regulate TP53 DNA methylation, mutations, and acetylation of TP53-related histones were methylated in CRC. P53 regulates the activity of numerous downstream proteins. Even if TP53 is not mutated, the function of wildtype p53 may be compromised if corresponding downstream genes are epigenetically inactivated. Thus, the role of p53 for CRC development, therapy response, and survival prognosis of patients may be much more eminent than previously estimated. Therefore, we propose that novel diagnostic devices measuring the entirety of genetic and epigenetic changes in the "p53 signalome" have the potential to improve the predictive and prognostic power in CRC diagnostics and management.

Targeting BRAF and RAS in Colorectal Cancer

Simple Summary

In colorectal cancer, mutations of the KRAS and BRAF genes are quite common and can contribute to the activation of cell signaling pathways that lead to cell proliferation and differentiation. These processes promote cancer growth, and in some cases, they may cause cells to develop resistance to certain types of treatment, notably EGFR inhibitors. We summarize recent knowledge regarding the effects of KRAS and BRAF mutations in the setting of colorectal cancer and discuss the new therapies under development.

Abstract

Colorectal cancer (CRC) is still one of the most frequent forms of cancer in the world in terms of incidence. Around 40% of CRC patients carry a mutation of the Kirsten rat sarcoma (KRAS) gene, while 10% have a mutation in the B-Raf proto-oncogene serine/threonine kinase (BRAF) gene. These mutations are responsible for dysregulation of the mitogen-associated protein kinase (MAPK) pathway, leading to the proliferation, differentiation, angiogenesis, and resistance to apoptosis of cells. Activation of the MAPK pathway results in adaptive therapeutic resistance, rendering EGFR inhibitors ineffective. This review aims to highlight the recent findings that have improved our understanding of KRAS and BRAF mutations in colorectal cancer and to describe new targeted therapies, used alone or in combination.

Promoter Hypermethylation of Wnt/β-catenin Signaling Pathway Inhibitor WIF-1 Gene and its Association with MTHFR C677T Polymorphism in Patients with Colorectal Cancer

OBJECTIVES

Colorectal cancer (CRC) is a common malignancy with a high rate of mortality. The dysregulation of genes involved in the Wnt/β-catenin signaling pathway is a common finding in cancers. Wnt-inhibitory factor-1 (WIF-1) suppresses the Wnt/β-catenin signaling pathway and its inactivation by genetics and epigenetic changes may cause cancer. We investigated the DNA methylation status of the WIF-1 gene in patients with CRC and its interaction with MTHFR C677T polymorphism, a known modifier of methylation reaction.

METHODS

We investigated 50 cancerous tissues and the adjacent non-cancerous tissue. Genomic DNA was extracted using a commercial kit and was treated by sodium bisulfite. Methylation-specific PCR was used for methylation analysis, and restriction fragment length polymorphism PCR to analyze the C677T polymorphism of the MTHFR gene.

RESULTS

The frequency of WIF1 promoter DNA methylation was significantly higher in cancerous tissue than adjacent non-cancerous tissue (52.0% vs. 8.0%; p < 0.001). WIF1 promoter DNA methylation status showed a significant association only with tumor location (p = 0.009). Carriers of TT genotype and T allele of MTHFR C677T polymorphism had a significantly higher frequency of unmethylated WIF1 gene than methylated WIF-1 gene in cancerous tissue (p = 0.025 and p = 0.001, respectively).

CONCLUSIONS

Promoter DNA hypermethylation of the WIF-1 gene is a significant risk factor for CRC development, which was significantly associated with tumor location only. The significant association of TT genotype and T allele of MTHFR C677T polymorphism with unmethylated WIF-1 gene suggests a protective role for this common polymorphism against methylation-induced development of CRC.

Weighted gene coexpression analysis indicates that PLAGL2 and POFUT1 are related to the differential features of proximal and distal colorectal cancer

In the current era of precision medicine, there is a general consensus that the anatomical site is an important factor in the management of colorectal cancer (CRC). To investigate the underlying molecular mechanisms between proximal and distal CRC and to identify the responsible genes, we analyzed the gene expression patterns of colorectal tumors from two microarray datasets, GSE39582 and GSE14333, on the NCBI Gene Expression Omnibus and the RNA‑seq data from TCGA. Weighted coexpression network analysis (WGCNA) was applied to construct a gene coexpression network. The red module in GSE39582 and the dark‑gray module from the TCGA dataset were found to be highly correlated with the anatomical site of CRC. A total of 12 hub genes were found in two datasets, 2 of which PLAG1 like zinc finger 2 (PLAGL2) and protein O‑fucosyltransferase 1 (POFUT1) were common and upregulated in tumor samples in CRC. The module with the highest correlation provided references that will help to characterize the difference between left‑sided and right‑sided CRC. The survival analysis of PLAGL2 and POFUT1 expression revealed differences between proximal and distal CRC. Gene set enrichment analysis based on those two genes provided similar results: GPI anchor biosynthesis and peroxisome and selenoamino acid metabolism. PLAGL2 and POFUT1, which have the highest correlation with tumor location, may serve as biomarkers and therapeutic targets for the precise diagnosis and treatment of CRC in the future.

Global differences in the prevalence of the CpG island methylator phenotype of colorectal cancer

Background

CpG Island Methylator Phenotype (CIMP) is an epigenetic phenotype in CRC characterized by hypermethylation of CpG islands in promoter regions of tumor suppressor genes, leading to their transcriptional silencing and loss of function. While the prevalence of CRC differs across geographical regions, no studies have compared prevalence of CIMP-High phenotype across regions. The purpose of this project was to compare the prevalence of CIMP across geographical regions after adjusting for variations in methodologies to measure CIMP in a meta-analysis.

Methods

We searched PubMed, Medline, and Embase for articles focusing on CIMP published from 2000 to 2018. Two reviewers independently identified 111 articles to be included in final meta-analysis. We classified methods used to quantify CIMP into 4 categories: a) Classical (MINT marker) Panel group b) Weisenberg-Ogino (W-O) group c) Human Methylation Arrays group and d) Miscellaneous group. We compared the prevalence of CIMP across geographical regions after correcting for methodological variations using meta-regression techniques.

Results

The pooled prevalence of CIMP-High across all studies was 22% (95% confidence interval:21–24%; I² = 94.75%). Pooled prevalence of CIMP-H across Asia, Australia, Europe, North America and South America was 22, 21, 21, 27 and 25%, respectively. Meta-regression analysis identified no significant differences in the prevalence of CIMP-H across geographical regions after correction for methodological variations. In exploratory analysis, we observed variations in CIMP-H prevalence across countries.

Conclusion

Although no differences were found for CIMP-H prevalence across countries, further studies are needed to compare the influence of demographic, lifestyle and environmental factors in relation to the prevalence of CIMP across geographical regions.

Investigating the methylation status of DACT2 gene and its association with MTHFR C677T polymorphism in patients with colorectal cancer

Colorectal cancer (CRC) is one of the common causes of cancer death in Iranian population. Both genetic and epigenetic changes have been implicated in CRC pathogenesis. DACT2 gene as one of the WNT signaling pathway inhibitor was shown to display tumor suppressor activity in many cancers. The aim of present study was to investigate the methylation status of DACT2 gene and its association with methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism in CRC patients. Fifty formalin-fixed paraffin-embedded cancerous and adjacent healthy tissues obtained from CRC patient were investigated. Genomic DNA was isolated using a FFPE commercial DNA extraction kit. The methylation status was evaluated by methylation specific PCR. Genotyping of MTHFR C677T polymorphism was performed using PCR-RFLP technique. Statistical analysis was done by GraphPad Prism 8. Results indicated that the frequency of methylated DACT2 gene was significantly higher in cancerous tissue relative to adjacent healthy tissue (P<0.001). DACT2 gene methylation was significantly more common among carriers of MTHFR 677CC genotype (P=0.035) and significantly less common among carriers of MTHFR 677T allele (P value =0.006). In conclusion the present study identified DACT2 gene methylation as a significant risk factor for CRC development. Moreover, the low frequency of DACT2 gene methylation among carriers of MTHFR 677T allele may confer a protective role for this common polymorphism against CRC risk.

Microarray‑based analysis of COL11A1 and TWIST1 as important differentially‑expressed pathogenic genes between left and right‑sided colon cancer

Colonic cancer has become a main reason of mortality associated with cancer; however, left and right-sided colonic cancer have diverse outcomes in terms of epidemiological, histological, clinical parameters and prognosis. We aimed to examine the discrepancies between these two types of colon cancers to identify potential therapeutic targets. In the present study, three gene expression profiles (GSE44076, GSE31595, GSE26906) from Gene Expression Omnibus (GEO) database were downloaded and further analyzed. A PPI (protein-protein interaction) network of the differentially-expressed genes (DEGs) of GSE44076 between tumor and normal was established with the Search Tool for the Retrieval of Interacting Genes database. Then, the DEGs of these two colon cancers (left, right) samples were identified. Subsequently, the intersection of DEGs of left and right-sided colon cancer samples obtained from three databases, and DEGs of tumor and normal samples were analyzed. Collagen type XI α1 chain (COL11A1), Twist family bHLH transcription factor 1 (TWIST1), insulin-like 5 and chromogranin A were upregulated proteins, while 3β-hydroxysteroid dehydrogenase was downregulated protein in right colon cancer than in left-sided tumor samples. Through further experimental verification, we revealed that COL11A1 and TWIST1 were significantly upregulated at the mRNA and protein levels within right-sided colon cancer compared with in left-sided colon cancer samples (P<0.05), consistent with bioinformatical analysis. Furthermore, a positive correlation between COL11A1 and TWIST1 protein expression was observed (P<0.0276). Collectively, our data showed that COL11A1 and TWIST1 may be potential prognostic indicators and molecular targets for the treatment of right-sided colon cancer.

Clinical, Pathological, and Molecular Characteristics of CpG Island Methylator Phenotype in Colorectal Cancer: A Systematic Review and Meta-analysis

BACKGROUND: CpG island methylator phenotype (CIMP) tumors, comprising 20% of colorectal cancers, are associated with female sex, age, right-sided location, and BRAF mutations. However, other factors potentially associated with CIMP have not been robustly examined. This meta-analysis provides a comprehensive assessment of the clinical, pathologic, and molecular characteristics that define CIMP tumors. METHODS: We conducted a comprehensive search of the literature from January 1999 through April 2018 and identified 122 articles, on which comprehensive data abstraction was performed on the clinical, pathologic, molecular, and mutational characteristics of CIMP subgroups, classified based on the extent of DNA methylation of tumor suppressor genes assessed using a variety of laboratory methods. Associations of CIMP with outcome parameters were estimated using pooled odds ratio or standardized mean differences using random-effects model. RESULTS: We confirmed prior associations including female sex, older age, right-sided tumor location, poor differentiation, and microsatellite instability. In addition to the recognized association with BRAF mutations, CIMP was also associated with PIK3CA mutations and lack of mutations in KRAS and TP53. Evidence of an activated immune response was seen with high rates of tumor-infiltrating lymphocytes (but not peritumoral lymphocytes), Crohn-like infiltrates, and infiltration with Fusobacterium nucleatum bacteria. Additionally, CIMP tumors were associated with advance T-stage and presence of perineural and lymphovascular invasion. CONCLUSION: The meta-analysis highlights key features distinguishing CIMP in colorectal cancer, including molecular characteristics of an active immune response. Improved understanding of this unique molecular subtype of colorectal cancer may provide insights into prevention and treatment.

Dietary fat and fiber interactively modulate apoptosis and mitochondrial bioenergetic profiles in mouse colon in a site-specific manner

We have demonstrated that the combination of bioactive components generated by fish oil (containing n-3 polyunsaturated fatty acids) and fermentable fiber (leading to butyrate production) act coordinately to protect against colon cancer. This is, in part, the result of an enhancement of apoptosis at the base of the crypt across all stages (initiation, promotion, and progression) of colon tumorigenesis. As mitochondria are key organelles capable of regulating the intrinsic apoptotic pathway and mediating programmed cell death, we investigated the effects of diet on mitochondrial function by measuring mucosal cardiolipin composition, mitochondrial respiratory parameters, and apoptosis in isolated crypts from the proximal and distal colon. C57BL/6 mice (n=15/treatment) were fed one of two dietary fats (corn oil and fish oil) and two fibers (pectin and cellulose) for 4 weeks in a 2×2 factorial design. In general, diet modulated apoptosis and the mucosal bioenergetic profiles in a site-specific manner. The fish/pectin diet promoted a more proapoptotic phenotype - for example, increased proton leak (Pinteraction=0.002) - compared with corn/cellulose (control) only in the proximal colon. With respect to the composition of cardiolipin, a unique phospholipid localized to the mitochondrial inner membrane where it mediates energy metabolism, fish oil feeding indirectly influenced its molecular species with a combined carbon number of C68 or greater, suggesting compensatory regulation. These data indicate that dietary fat and fiber can interactively modulate the mitochondrial metabolic profile and thereby potentially modulate apoptosis and subsequent colon cancer risk.

Differences in Cancer-Specific Mortality of Right- Versus Left-Sided Colon Adenocarcinoma: A Surveillance, Epidemiology, and End Results Database Analysis

Purpose

Studies have shown an increased risk for all-cause mortality with right-sided colon cancer (RCC) as compared with left-sided colon cancer (LCC). However, these studies were unable to directly account for mortality events unrelated to cancer, known as other-cause mortality. We investigated the difference in cancer-specific mortality (CSM) between RCC and LCC at localized, regional, and metastatic stages, according to the Fine and Gray proportional hazards model, while accounting for other-cause mortality as a competing risk.

Methods

Using the SEER database, we identified 90,635 patients with LCC (ie, involving the splenic flexure, descending, sigmoid, and rectosigmoid colon) and 112,679 patients with RCC (ie, involving the cecum, ascending, hepatic flexure, and transverse colon) diagnosed from 1998 to 2013. We performed a competing risk analysis for CSM using the Fine and Gray proportional hazard model, adjusting for age, sex, race, tumor grade, surgery status, year of diagnosis, and tumor laterality, with two-sided testing and a statistical significance threshold of 0.05.

Results

Compared with LCC, RCC demonstrated statistically significant decreased CSM at the localized stage (adjusted hazards ratio [AHR], 0.865; P < .001), equivalent CSM at the regional stage (AHR, 0.990; P = .440), and increased CSM at the metastatic stage (AHR, 1.175; P < .001).

Conclusion

Using a competing risk model, we have shown that RCC, compared with LCC, is associated with lower CSM at the localized stage, equivalent CSM at the regional stage, and higher CSM at the metastatic stage. This pattern may correlate with variation in genetic factors, including known decreased prevalence of microsatellite instability in RCC with regional and metastatic disease.

Clinical and prognosis value of the CIMP status combined with MLH1 or p16 INK4a methylation in colorectal cancer

Aberrant DNA methylation of CpG islands occurred frequently in CRC and associated with transcriptional silencing of key genes. In this study, the CIMP combined with MLH1 or p16 ^INK4a methylation status was determined in CRC patients and correlated with clinicopathological parameters and overall survival. Our data showed that CIMP+ CRCs were identified in 32.9% of cases and that CACNAG1 is the most frequently methylated promoter. When we combined the CIMP with the MLH1 or the p16 ^INK4a methylation status, we found that CIMP-/MLH1-U (37.8%) and CIMP-/p16 ^INK4a -U (35.4%) tumors were the most frequent among the four subtypes. Statistical analysis showed that tumor location, lymphovascular invasion, TNM stage, and MSI differed among the group of patients. Kaplan-Meier analyses revealed differences in overall survival according to the CIMP combined with MLH1 or p16 ^INK4a methylation status. In a multivariate analysis, CIMP/MLH1 and CIMP/p16 ^INK4a methylation statuses were predictive of prognosis, and the OS was longer for patients with tumors CIMP-/MLH1-M, as well as CIMP-/p16 ^INK4a -M. Furthermore, DNMT1 is significantly overexpressed in tumors than in normal tissues as well as in CIMP+ than CIMP- tumors. Our results suggest that tumor classification based on the CIMP status combined with MLH1 or p16 ^INK4a methylation is useful to predict prognosis in CRC patients.

BRAF mutation is associated with poor clinicopathological outcomes in colorectal cancer: A meta-analysis

BACKGROUND/AIMS

The clinical relevance of the BRAF mutation in colorectal carcinoma (CRC) remains controversial. We performed a comprehensive meta-analysis to evaluate the precise relationship of BRAF mutation to clinicopathological features.

MATERIALS AND METHODS

A systematic search of the electronic databases, including PubMed, the Web of Knowledge, and the China Journal Net was performed between January 2005 and December 2015. Outcomes of interest included gender, tumor site, tumor differentiation, node involvement, tumor size, and AJCC stage. We calculated the pooled odds ratios (ORs) or risk ratios with 95% confidence intervals (CIs) for each study using a random or fixed-effect model.

RESULTS

Twenty-five studies with a total of 13208 patients were included. BRAF mutation-positive CRC patients were 1464 (11.1%). Our meta-analysis revealed that, in patients with CRC, the BRAF mutation was associated with female, proximal site, poor differentiation, >5 cm size, and advanced AJCC stage.

CONCLUSIONS

This meta-analysis demonstrated that BRAF mutation was closely related to adverse pathological features and poor outcome of CRC.

Comprehensive site-specific whole genome profiling of stromal and epithelial colonic gene signatures in human sigmoid colon and rectal tissue

The strength of associations between various exposures (e.g., diet, tobacco, chemopreventive agents) and colorectal cancer risk may partially depend on the complex interaction between epithelium and stroma across anatomic subsites. Currently, baseline data describing genome-wide coding and long noncoding gene expression profiles in the healthy colon specific to tissue type and location are lacking. Therefore, colonic mucosal biopsies from 10 healthy participants who were enrolled in a clinical study to evaluate effects of lignan supplementation on gut resiliency were used to characterize the site-specific global gene expression signatures associated with stromal vs. epithelial cells in the sigmoid colon and rectum. Using RNA-seq, we demonstrate that tissue type and location patterns of gene expression and upstream regulatory pathways are distinct. For example, consistent with a key role of stroma in the crypt niche, mRNAs associated with immunoregulatory and inflammatory processes (i.e., CXCL14, ANTXR1), smooth muscle contraction (CALD1), proliferation and apoptosis (GLP2R, IGFBP3), and modulation of extracellular matrix (MMP2, COL3A1, MFAP4) were all highly expressed in the stroma. In comparison, HOX genes (HOXA3, HOXD9, HOXD10, HOXD11, and HOXD-AS2, a HOXD cluster antisense RNA 2), and WNT5B expression were also significantly higher in sigmoid colon compared with the rectum. These findings provide strong impetus for considering colorectal tissue subtypes and location in future observational studies and clinical trials designed to evaluate the effects of exposures on colonic health.

Colorectal cancer mortality trends in Serbia during 1991-2010: an age-period-cohort analysis and a joinpoint regression analysis

BACKGROUND

For both men and women worldwide, colorectal cancer is among the leading causes of cancer-related death. This study aimed to assess the mortality trends of colorectal cancer in Serbia between 1991 and 2010, prior to the introduction of population-based screening.

METHODS

Joinpoint regression analysis was used to estimate average annual percent change (AAPC) with the corresponding 95% confidence interval (CI). Furthermore, age-period-cohort analysis was performed to examine the effects of birth cohort and calendar period on the observed temporal trends.

RESULTS

We observed a significantly increased trend in colorectal cancer mortality in Serbia during the study period (AAPC = 1.6%, 95% CI 1.3%-1.8%). Colorectal cancer showed an increased mortality trend in both men (AAPC = 2.0%, 95% CI 1.7%-2.2%) and women (AAPC = 1.0%, 95% CI 0.6%-1.4%). The temporal trend of colorectal cancer mortality was significantly affected by birth cohort (P < 0.05), whereas the study period did not significantly affect the trend (P = 0.072). Colorectal cancer mortality increased for the first several birth cohorts in Serbia (from 1916 to 1955), followed by downward flexion for people born after the 1960s. According to comparability test, overall mortality trends for colon cancer and rectal and anal cancer were not parallel (the final selected model rejected parallelism, P < 0.05).

CONCLUSIONS

We found that colorectal cancer mortality in Serbia increased considerably over the past two decades. Mortality increased particularly in men, but the trends were different according to age group and subsite. In Serbia, interventions to reduce colorectal cancer burden, especially the implementation of a national screening program, as well as treatment improvements and measures to encourage the adoption of a healthy lifestyle, are needed.

SNP rs16906252C>T Is an Expression and Methylation Quantitative Trait Locus Associated with an Increased Risk of Developing MGMT-Methylated Colorectal Cancer

PURPOSE

Methylation of the MGMT promoter is the major cause of O⁶-methylguanine methyltransferase deficiency in cancer and has been associated with the T variant of the promoter enhancer SNP rs16906252C>T. We sought evidence for an association between the rs16906252C>T genotype and increased risk of developing a subtype of colorectal cancer featuring MGMT methylation, mediated by genotype-dependent epigenetic silencing within normal tissues.

EXPERIMENTAL DESIGN

By applying a molecular pathologic epidemiology case-control study design, associations between rs16906252C>T and risk for colorectal cancer overall, and colorectal cancer stratified by MGMT methylation status, were estimated using multinomial logistic regression in two independent retrospective series of colorectal cancer cases and controls. The test sample comprised 1,054 colorectal cancer cases and 451 controls from Sydney, Australia. The validation sample comprised 612 colorectal cancer cases and 245 controls from the Australasian Colon Cancer Family Registry (ACCFR). To determine whether rs16906252C>T was linked to a constitutively altered epigenetic state, quantitative allelic expression and methylation analyses were performed in normal tissues.

RESULTS

An association between rs16906252C>T and increased risk of developing MGMT-methylated colorectal cancer in the Sydney sample was observed [OR, 3.3; 95% confidence interval (CI), 2.0-5.3; P < 0.0001], which was replicated in the ACCFR sample (OR, 4.0; 95% CI, 2.4-6.8; P < 0.0001). The T allele demonstrated about 2.5-fold reduced transcription in normal colorectal mucosa from cases and controls and was selectively methylated in a minority of normal cells, indicating that rs16906252C>T represents an expression and methylation quantitative trait locus.

CONCLUSIONS

We provide evidence that rs16906252C>T is associated with elevated risk for MGMT-methylated colorectal cancer, likely mediated by constitutive epigenetic repression of the T allele. Clin Cancer Res; 22(24); 6266-77. ©2016 AACR.

The Incidence Characteristics of Second Primary Malignancy after Diagnosis of Primary Colon and Rectal Cancer: A Population Based Study

BACKGROUND

With the expanding population of colorectal cancer (CRC) survivors in the United States, one concerning issue is the risk of developing second primary malignancies (SPMs) for these CRC survivors. The present study attempts to identify the incidence characteristics of SPMs after diagnosis of first primary colon cancer (CC) and rectal cancer (RC).

METHODS

189,890 CC and 83,802 RC cases were identified from Surveillance, Epidemiology and End Results Program (SEER) database. We performed rate analysis on incidence trend of SPMs in both CC and RC. Expected incidence rates were stratified by age, race and stage, calendar year of first CRC diagnosis and latency period since first CRC diagnosis. The standardized incidence ratios (SIRs), measure for estimating risk of SPMs, were calculated for CC and RC respectively.

RESULTS

The trends of incidence of SPMs in both CC and RC were decreasing from 1992 to 2012. Both CC and RC survivors had higher risk of developing SPMs (SIRCC = 1.13; SIRRC = 1.05). For CC patients, the highest risks of SPM were cancers of small intestine (SIR = 4.03), colon (SIR = 1.87) and rectum (SIR = 1.80). For RC patients, the highest risks of SPMs were cancers of rectum (SIR = 2.88), small intestine (SIR = 2.16) and thyroid (SIR = 1.46). According to stratified analyses, we also identified incidence characteristics which were contributed to higher risk of developing SPMs, including the age between 20 and 40, American Indian/Alaska Native, localized stage, diagnosed at calendar year from 2002 to 2012 and the latency between 12 and 59 months.

CONCLUSIONS

Both CC and RC survivors remain at higher risk of developing SPMs. The identification of incidence characteristics of SPMs is extremely essential for continuous cancer surveillance among CRC survivors.

Epigenetics and Colorectal Neoplasia: the Evidence for Physical Activity and Sedentary Behavior

Studies demonstrate that regular physical activity and, more recently, limited sedentary behavior are associated with reduced risk of colorectal neoplasia. However, the biological mechanisms of action for physical activity versus sedentary behavior are not clear. Epigenetic variation is suggested as a potential mechanism that would allow for independent, or possibly even synergistic, effects of activity and inactivity on colorectal epithelium. We describe the evidence for epigenetic variation as a link between physical activity and sedentary behavior in colorectal neoplasia risk. There are few studies that directly evaluate this relationship. However, the growing literature describes a variety of gene targets influenced by activity that are also important to colorectal neoplasia etiology. Future studies may identify epigenetic markers with translational significance in identifying high-risk individuals or those for whom a personalized activity regimen could significantly alter the methylation signature in colon epithelial cells, and thus future risk of colorectal cancer.

A survey of tandem repeat instabilities and associated gene expression changes in 35 colorectal cancers

BACKGROUND

Colorectal cancer is a major contributor to cancer morbidity and mortality. Tandem repeat instability and its effect on cancer phenotypes remain so far poorly studied on a genome-wide scale.

RESULTS

Here we analyze the genomes of 35 colorectal tumors and their matched normal (healthy) tissues for two types of tandem repeat instability, de-novo repeat gain or loss and repeat copy number variation. Specifically, we study for the first time genome-wide repeat instability in the promoters and exons of 18,439 genes, and examine the association of repeat instability with genome-scale gene expression levels. We find that tumors with a microsatellite instable (MSI) phenotype are enriched in genes with repeat instability, and that tumor genomes have significantly more genes with repeat instability compared to healthy tissues. Genes in tumor genomes with repeat instability in their promoters are significantly less expressed and show slightly higher levels of methylation. Genes in well-studied cancer-associated signaling pathways also contain significantly more unstable repeats in tumor genomes. Genes with such unstable repeats in the tumor-suppressor p53 pathway have lower expression levels, whereas genes with repeat instability in the MAPK and Wnt signaling pathways are expressed at higher levels, consistent with the oncogenic role they play in cancer.

CONCLUSIONS

Our results suggest that repeat instability in gene promoters and associated differential gene expression may play an important role in colorectal tumors, which is a first step towards the development of more effective molecular diagnostic approaches centered on repeat instability.

Associations of anthropometric factors with KRAS and BRAF mutation status of primary colorectal cancer in men and women: a cohort study

Obesity is a well-established risk factor for colorectal cancer (CRC), and accumulating evidence suggests a differential influence of sex and anthropometric factors on the molecular carcinogenesis of the disease. The aim of the present study was to investigate the relationship between height, weight, bodyfat percentage, waist- and hip circumference, waist-hip ratio (WHR), body mass index (BMI) and CRC risk according to KRAS and BRAF mutation status of the tumours, with particular reference to potential sex differences. KRAS and BRAF mutations were analysed by pyrosequencing in tumours from 494 incident CRC cases in the Malmö Diet and Cancer Study. Hazard ratios of CRC risk according to anthropometric factors and mutation status were calculated using multivariate Cox regression models. While all anthropometric measures except height were associated with an increased risk of KRAS-mutated tumours, only BMI was associated with an increased risk of KRAS wild type tumours overall. High weight, hip, waist, WHR and BMI were associated with an increased risk of BRAF wild type tumours, but none of the anthropometric factors were associated with risk of BRAF-mutated CRC, neither in the overall nor in the sex-stratified analysis. In men, several anthropometric measures were associated with both KRAS-mutated and KRAS wild type tumours. In women, only a high WHR was significantly associated with an increased risk of KRAS-mutated CRC. A significant interaction was found between sex and BMI with respect to risk of KRAS-mutated tumours. In men, all anthropometric factors except height were associated with an increased risk of BRAF wild type tumours, whereas in women, only bodyfat percentage was associated with an increased risk of BRAF wild type tumours. The results from this prospective cohort study further support an influence of sex and lifestyle factors on different pathways of colorectal carcinogenesis, defined by KRAS and BRAF mutation status of the tumours.

Genome-wide analysis of the rat colon reveals proximal-distal differences in histone modifications and proto-oncogene expression

Since disease susceptibility of the intestine exhibits an anatomical bias, we propose that the chromatin landscape, especially the site-specific epigenetic differences in histone modification patterns throughout the colonic longitudinal axis, contributes to the differential incidence of site-specific pathology. To test this hypothesis, we assessed the chromatin structure associated with gene expression profiles in the rat proximal and distal colon by globally correlating chromatin immunoprecipitation next-generation sequencing analysis (ChIP-Seq) with mRNA transcription (RNA-Seq) data. Crypts were isolated from the proximal and distal colonic regions from rats maintained on a semipurified diet, and mRNA gene expression profiles were generated by RNA-Seq. The remaining isolated crypts were formaldehyde-cross-linked and chromatin immunoprecipitated with antibodies against H3K4me3, H3K9me3, and RNA polymerase II. Globally, RNA-Seq results indicate that 9,866 genes were actively expressed, of which 540 genes were differentially expressed between the proximal and distal colon. Gene ontology analysis indicates that crypt location significantly affected both chromatin and transcriptional regulation of genes involved in enterocyte movement, lipid metabolism, lymphatic development, and immune cell trafficking. Gene function analysis indicates that the PI3-kinase signaling pathway was regulated in a site-specific manner, e.g., proto-oncogenes, JUN, FOS, and ATF, were upregulated in the distal colon. Middle and long noncoding RNAs (lncRNAs) were also detected in the colon, including select lncRNAs formerly only detected in the rat nervous system. In summary, distinct combinatorial patterns of histone modifications exist in the proximal versus distal colon. These site-specific differences may explain the differential effects of chemoprotective agents on cell transformation in the ascending (proximal) and descending (distal) colon.

BRAF mutation is associated with distinct clinicopathological characteristics in colorectal cancer: a systematic review and meta-analysis

AIM

Colorectal cancer is a heterogeneous disease with multiple underlying genetic mutations resulting in different phenotypes. Mutation in the v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) proto-oncogene is an important event in the methylator pathway. There is no consensus, however, on the clinicopathological characteristics associated with BRAF mutation.

METHOD

A comprehensive search for published studies examining the effect of BRAF mutation on colorectal cancer was performed. Random effects methods were used to combine data.

RESULTS

Data were retrieved from 21 studies describing 9885 patients. BRAF associated colorectal cancer is associated with proximal tumour location (OR 5.222, 95% CI 3.801-7.174, P < 0.001), T4 tumours (OR 1.761, 95% CI 1.164-2.663, P = 0.007) and poor differentiation (OR 3.816, 95% CI 2.714-5.365, P < 0.001) and is negatively associated with male sex (OR 0.623, 95% CI 0.505-0.769, P < 0.001), age of diagnosis under 60 years (OR 0.453, 95% CI 0.280-0.733, P = 0.001) and rectal cancer (OR 0.266, 95% CI 0.122-0.422, P < 0.001).

CONCLUSION

BRAF mutation appears to be associated with distinct, unfavourable clinicopathological characteristics in colorectal cancer.

Associations between colorectal cancer molecular markers and pathways with clinicopathologic features in older women

BACKGROUND & AIMS

Colorectal tumors have a large degree of molecular heterogeneity. Three integrated pathways of carcinogenesis (ie, traditional, alternate, and serrated) have been proposed, based on specific combinations of microsatellite instability (MSI), CpG island methylator phenotype (CIMP), and mutations in BRAF and KRAS. We used resources from the population-based Iowa Women's Health Study (n = 41,836) to associate markers of colorectal tumors, integrated pathways, and clinical and pathology characteristics, including survival times.

METHODS

We assessed archived specimens from 732 incident colorectal tumors and characterized them as microsatellite stable (MSS), MSI high or MSI low, CIMP high or CIMP low, CIMP negative, and positive or negative for BRAF and/or KRAS mutations. Informative marker data were collected from 563 tumors (77%), which were assigned to the following integrated pathways: traditional (MSS, CIMP negative, BRAF mutation negative, and KRAS mutation negative; n = 170), alternate (MSS, CIMP low, BRAF mutation negative, and KRAS mutation positive; n = 58), serrated (any MSI, CIMP high, BRAF mutation positive, and KRAS mutation negative; n = 142), or unassigned (n = 193). Multivariable-adjusted Cox proportional hazards regression models were used to assess the associations of interest.

RESULTS

Patients' mean age (P = .03) and tumors' anatomic subsite (P = .0001) and grade (P = .0001) were significantly associated with integrated pathway assignment. Colorectal cancer (CRC) mortality was not associated with the traditional, alternate, or serrated pathways, but was associated with a subset of pathway-unassigned tumors (MSS or MSI low, CIMP negative, BRAF mutation negative, and KRAS mutation positive) (n = 96 cases; relative risk = 1.76; 95% confidence interval, 1.07-2.89, compared with the traditional pathway).

CONCLUSIONS

We identified clinical and pathology features associated with molecularly defined CRC subtypes. However, additional studies are needed to determine how these features might influence prognosis.

Colon and rectal cancer survival by tumor location and microsatellite instability: the Colon Cancer Family Registry

BACKGROUND

Cancers in the proximal colon, distal colon, and rectum are frequently studied together; however, there are biological differences in cancers across these sites, particularly in the prevalence of microsatellite instability.

OBJECTIVE

We assessed the differences in survival by colon or rectal cancer site, considering the contribution of microsatellite instability to such differences.

DESIGN

This is a population-based prospective cohort study for cancer survival.

SETTINGS

This study was conducted within the Colon Cancer Family Registry, an international consortium. Participants were identified from population-based cancer registries in the United States, Canada, and Australia.

PATIENTS

Information on tumor site, microsatellite instability, and survival after diagnosis was available for 3284 men and women diagnosed with incident invasive colon or rectal cancer between 1997 and 2002, with ages at diagnosis ranging from 18 to 74.

MAIN OUTCOME MEASURES

Cox regression was used to calculate hazard ratios for the association between all-cause mortality and tumor location, overall and by microsatellite instability status.

RESULTS

Distal colon (HR, 0.59; 95% CI, 0.49-0.71) and rectal cancers (HR, 0.68; 95% CI, 0.57-0.81) were associated with lower mortality than proximal colon cancer overall. Compared specifically with patients with proximal colon cancer exhibiting no/low microsatellite instability, patients with distal colon and rectal cancers experienced lower mortality, regardless of microsatellite instability status; patients with proximal colon cancer exhibiting high microsatellite instability had the lowest mortality.

LIMITATIONS

Study limitations include the absence of stage at diagnosis and cause-of-death information for all but a subset of study participants. Some patient groups defined jointly by tumor site and microsatellite instability status are subject to small numbers.

CONCLUSION

Proximal colon cancer survival differs from survival for distal colon and rectal cancer in a manner apparently dependent on microsatellite instability status. These findings support the premise that proximal colon, distal colon, and rectal cancers are clinicopathologically distinct.

Factors associated with the risk of adenoma recurrence in distal and proximal colon

BACKGROUND/AIMS

Colonoscopy may be less effective in preventing cancer in the proximal colon. We evaluated whether risk factors for adenoma recurrence exhibit differential effect on adenoma recurrence by colon subsite.

METHODS

We examined the association of age, sex, body mass index, smoking status and use of nonsteroidal anti-inflammatory drugs (NSAIDs) on proximal and distal adenoma recurrence among 1,864 participants in the Polyp Prevention Trial. We used multinomial logistic regression models to calculate the relative risk ratios (RRR) and 95% CI.

RESULTS

733 (39.3%) participants had adenoma recurrence (228 distal only, 369 proximal only and 136 synchronous proximal and distal adenoma). When compared to participants without adenoma recurrence, no factor was associated with an increased risk of distal only adenoma recurrence. Age 65-69 years (RRR = 1.47, 95% CI 1.00-2.16), age ≥70 years (RRR = 2.24, 95% CI 1.57-3.20), and male sex (RRR = 1.73, 95% CI 1.32-2.27) were positively associated with proximal only adenoma recurrence. NSAIDs use was associated with a reduced risk of adenoma recurrence by similar magnitude in distal (RRR = 0.78, 95% CI 0.58-1.07) and proximal colon (RRR = 0.77, 95% CI 0.60-1.00).

CONCLUSIONS

We did not find any modifiable risk factor that differentially increases proximal as compared to distal adenoma recurrence to be clinically useful for targeted intervention.

Contribution of behavioral risk factors and obesity to socioeconomic differences in colorectal cancer incidence

BACKGROUND

Health behaviors are known risk factors for colorectal cancer and are more common in low socioeconomic status (SES) populations. We evaluated the extent to which behavioral risk factors and body mass index (BMI) explain SES disparities in colorectal cancer incidence, overall and by tumor location.

METHODS

We analyzed prospective National Institutes of Health-AARP Diet and Health Study data on 506 488 participants who were recruited in 1995-1996 from six US states and two metropolitan areas and followed through 2006. Detailed baseline data on risk factors for colorectal cancer, including health behaviors, were obtained using questionnaires. SES was measured by self-reported education and census-tract data. The outcome was primary incident invasive colorectal adenocarcinoma. Poisson regression was used to estimate the association between SES and risk of incident colorectal cancer, with adjustment for age, sex, race and ethnicity, family history, and state of residence. The model estimates were used to derive percentage mediation by behavioral risk factors; bias-corrected 95% confidence intervals were obtained through bootstrap techniques.

RESULTS

Seven-thousand six-hundred seventy-six participants developed colorectal cancer during follow-up. SES differences in prevalence of physical inactivity, unhealthy diet, smoking, and unhealthy weight each explained between 11.3% (BMI) and 21.6% (diet) of the association between education and risk of colorectal cancer and between 8.6% (smoking) and 15.3% (diet) of the association between neighborhood SES and risk of colorectal cancer. Health behaviors and BMI combined explained approximately 43.9% (95% CI = 35.1% to 57.9%) of the association of education and 36.2% (95% CI = 28.0% to 51.2%) of the association of neighborhood SES with risk of colorectal cancer. The percentage explained by all factors and BMI combined was largest for right colon cancers and smallest for rectal cancers.

CONCLUSION

A substantial proportion of the socioeconomic disparity in risk of new-onset colorectal cancer, and particularly of right colon cancers, may be attributable to the higher prevalence of adverse health behaviors in low-SES populations.

Influence of anatomical subsite on the incidence of microsatellite instability, and KRAS and BRAF mutation rates in patients with colon carcinoma

There is a growing amount of data supporting the concept that cancers originating from the proximal and distal colon are distinct clinicopathological entities. The incidence of MSI and BRAF mutation is strongly associated with right sided tumor location, whereas there are conflicting results for KRAS mutation rates. However, to date, no data exist whether and to what extent defined colonic subsites influence MSI status, KRAS and BRAF mutation rates. We selected primary colon cancer from 171 patients operated on at our institution between 2007 and 2010. BRAF, KRAS mutation rates and microsatellite instability were determined and correlated with clinicopathological features and tumor location. MSI-h cancers were significantly associated with poor histological grade but a lower rate of distant metastases. KRAS-mutated tumors were linked to lower T-stage and better differentiation. Colon carcinomas with BRAF mutation were significantly associated with distant metastatic spread and poor histological grade. Furthermore, we found that MSI-h status, KRAS and BRAF mutation rates varied remarkably among the colonic subsites irrespective of right- and left-sided origin, respectively. The results of the current study provide further evidence that a simple classification into right- and left-sided colon carcinoma does not represent the complexity of this tumor entity.

Concerns and challenges in flexible sigmoidoscopy screening

In 1992, two well-conducted case-control studies used data from two different health maintenance organizations and demonstrated a 59-79% reduction in mortality from colorectal cancer (CRC) following exposure to sigmoidoscopy. These studies highlight the possibility of reducing mortality from CRC using population-based endoscopic screening. The development of fiber optics improved the technology, and the ease of performing flexible sigmoidoscopy (FS) with widespread adoption of this screening modality. To date, FS is the only endoscopic screening modality that has been shown to reduce mortality in randomized clinical trials. This article reviews the development of sigmoidoscopy, its use in CRC screening and the current reduced role of this proven screening modality, and explores new frontiers for population-based FS screening.

BRAF-mutated, microsatellite-stable adenocarcinoma of the proximal colon: an aggressive adenocarcinoma with poor survival, mucinous differentiation, and adverse morphologic features

The association of BRAF V600E mutation and the presence of the CpG island methylator phenotype (CIMP) and microsatellite instability (MSI) often confound analysis of BRAF mutation status and survival in colorectal carcinoma. We evaluated a consecutive series of proximal colonic adenocarcinomas for mismatch repair protein abnormalities/MSI, BRAF V600E mutation, and KRAS mutations in an attempt to determine the prognostic significance of these abnormalities and to correlate histopathologic features with molecular alterations. Of the 259 proximal colon adenocarcinomas analyzed for mismatch repair protein abnormalities and/or MSI, 181 proximal colonic adenocarcinomas demonstrated proficient DNA mismatch repair using either MSI PCR (n=78), mismatch repair protein immunohistochemistry (n=91), or both MSI PCR and mismatch repair immunohistochemistry (n=12); these were tested for the BRAF V600E mutation and KRAS mutations. Compared with BRAF wild-type adenocarcinomas, BRAF-mutated adenocarcinomas more frequently demonstrated adverse histologic features such as lymphatic invasion (16/20, 80% vs. 75/161, 47%; P=0.008), mean number of lymph node metastases (4.5 vs. 2.2; P=0.01), perineural invasion (8/20, 40% vs. 13/161, 8%; P=0.0004), and high tumor budding (16/20, 80% vs. 83/161, 52%; P=0.02). BRAF-mutated adenocarcinomas frequently contained areas with mucinous histology (P=0.0002) and signet ring histology (P=0.03), compared with KRAS-mutated and KRAS/BRAF wild-type adenocarcinomas. Clinical follow-up data were available for 173 proximal colonic adenocarcinomas with proficient DNA mismatch repair. Patients with BRAF-mutated adenocarcinomas had a median survival of 12.3 months with a 1-year probability of survival of 54% and a 1-year disease-free survival of 56%. Patients with KRAS-mutated and KRAS/BRAF wild-type adenocarcinomas had significantly improved overall survival (unadjusted log-rank P=0.03 and unadjusted log-rank P=0.0002, respectively) and disease-free survival (unadjusted log-rank P=0.02 and unadjusted log-rank P=0.02, respectively) compared with patients with BRAF-mutated adenocarcinomas. When adjusting for tumor stage, survival analysis demonstrated that patients with BRAF-mutated adenocarcinoma had a significantly poor overall survival and disease-free survival (hazard ratios 6.63, 95% CI, 2.60-16.94; and 6.08, 95% CI, 2.11-17.56, respectively) compared with patients with KRAS/BRAF wild-type adenocarcinomas. No significant difference in overall or disease-free survival was identified between patients with KRAS-mutated and KRAS/BRAF wild-type adenocarcinomas. Our results demonstrate that BRAF-mutated proximal colon adenocarcinomas with proficient DNA mismatch repair have a dismal prognosis with an aggressive clinical course and often display mucinous differentiation, focal signet ring histology, and other adverse histologic features such as lymphatic and perineural invasion and high tumor budding.

Colorectal-cancer incidence and mortality with screening flexible sigmoidoscopy

BACKGROUND

The benefits of endoscopic testing for colorectal-cancer screening are uncertain. We evaluated the effect of screening with flexible sigmoidoscopy on colorectal-cancer incidence and mortality.

METHODS

From 1993 through 2001, we randomly assigned 154,900 men and women 55 to 74 years of age either to screening with flexible sigmoidoscopy, with a repeat screening at 3 or 5 years, or to usual care. Cases of colorectal cancer and deaths from the disease were ascertained.

RESULTS

Of the 77,445 participants randomly assigned to screening (intervention group), 83.5% underwent baseline flexible sigmoidoscopy and 54.0% were screened at 3 or 5 years. The incidence of colorectal cancer after a median follow-up of 11.9 years was 11.9 cases per 10,000 person-years in the intervention group (1012 cases), as compared with 15.2 cases per 10,000 person-years in the usual-care group (1287 cases), which represents a 21% reduction (relative risk, 0.79; 95% confidence interval [CI], 0.72 to 0.85; P<0.001). Significant reductions were observed in the incidence of both distal colorectal cancer (479 cases in the intervention group vs. 669 cases in the usual-care group; relative risk, 0.71; 95% CI, 0.64 to 0.80; P<0.001) and proximal colorectal cancer (512 cases vs. 595 cases; relative risk, 0.86; 95% CI, 0.76 to 0.97; P=0.01). There were 2.9 deaths from colorectal cancer per 10,000 person-years in the intervention group (252 deaths), as compared with 3.9 per 10,000 person-years in the usual-care group (341 deaths), which represents a 26% reduction (relative risk, 0.74; 95% CI, 0.63 to 0.87; P<0.001). Mortality from distal colorectal cancer was reduced by 50% (87 deaths in the intervention group vs. 175 in the usual-care group; relative risk, 0.50; 95% CI, 0.38 to 0.64; P<0.001); mortality from proximal colorectal cancer was unaffected (143 and 147 deaths, respectively; relative risk, 0.97; 95% CI, 0.77 to 1.22; P=0.81).

CONCLUSIONS

Screening with flexible sigmoidoscopy was associated with a significant decrease in colorectal-cancer incidence (in both the distal and proximal colon) and mortality (distal colon only). (Funded by the National Cancer Institute; PLCO ClinicalTrials.gov number, NCT00002540.).

Association of dietary quercetin with reduced risk of proximal colon cancer

Quercetin is a flavonol that appears to be protective against several cancers, but its possible role in prevention of colorectal cancer is not yet well studied. We evaluated dietary intakes of quercetin and risk of colorectal cancer in a large case-control study conducted in metropolitan Detroit, Michigan (N = 2664). The protective effects of quercetin intake, as assessed by a food frequency questionnaire, were confined to risk of proximal colon cancer. Stratified analyses showed that the protective effects of quercetin on risk of proximal colon cancer were significant only when fruit intake or the Healthy Eating Index score was high, or when tea intake was low, with odds ratios (OR) for the highest vs. the lowest quartile of 0.49, 0.44, and 0.51, respectively. Increased quercetin intake had no protective effects when tea intake was high. Interestingly, increased intake of quercetin was associated with increased risk of distal colon cancer when total fruit intake was low (OR for the highest vs. the lowest quartile = 1.99). These results suggest that quercetin can have disparate effects on colon cancer risk depending on whether dietary intakes of fruit or tea are high, and that quercetin had protective effects only on proximal, not distal, colon cancer.

BRAF mutation is a prognostic biomarker for colorectal liver metastasectomy

BACKGROUND AND OBJECTIVES

In metastatic colorectal cancer, v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) is a predictive biomarker for anti-epidermal growth factor receptor (EGFR) treatment and V-raf murine sarcoma viral oncogene homolog B1 (BRAF) is a prognostic biomarker. We aimed to determine the impact of KRAS and BRAF mutation as determined from liver metastases specimens on overall survival (OS) in patients following colorectal liver metastasectomy.

METHODS

Liver metastases specimens (n = 292) obtained from patients after liver metastasectomy were used to determine the KRAS/BRAF genotype. Associations between clinicopathological parameters and KRAS/BRAF genotype were identified by univariate and multivariate analyses using the Cox proportional hazards model. The impact of KRAS/BRAF genotype on survival was analyzed using the Kaplan-Meier method.

RESULTS

The 5-year survival rate of the cohort was 55.8%. The KRAS and BRAF mutation rates were 38.0 and 2.1%, respectively. BRAF genotype, but not KRAS, was found to be an independent prognostic biomarker (HR = 5.181, P = 0.002) after adjustment for other significant confounding clinicopathological variates: Number of liver metastases (HR = 1.983, P = 0.009), concomitant extrahepatic disease (HR = 1.858, P = 0.014), and surgical margin (HR = 3.241, P < 0.001). BRAF genotype was an independent prognostic biomarker in patients with liver metastases only after metastasectomy (HR = 6.245, P < 0.003).

CONCLUSIONS

BRAF mutation is an independent prognostic biomarker for colorectal liver metastasectomy.

Are KRAS/BRAF mutations potent prognostic and/or predictive biomarkers in colorectal cancers?

KRAS and BRAF mutations lead to the constitutive activation of EGFR signaling through the oncogenic Ras/Raf/Mek/Erk pathway. Currently, KRAS is the only potential biomarker for predicting the efficacy of anti-EGFR monoclonal antibodies (mAb) in colorectal cancer (CRC). However, a recent report suggested that the use of cetuximab was associated with survival benefit among patients with p.G13D-mutated tumors. Furthermore, although the presence of mutated BRAF is one of the most powerful prognostic factors for advanced and recurrent CRC, it remains unknown whether patients with BRAF-mutated tumors experience a survival benefit from treatment with anti-EGFR mAb. Thus, the prognostic or predictive relevance of the KRAS and BRAF genotype in CRC remains controversial despite several investigations. Routine KRAS/BRAF screening of pathological specimens is required to promote the appropriate clinical use of anti-EGFR mAb and to determine malignant phenotypes in CRC. The significance of KRAS/BRAF mutations as predictive or prognostic biomarkers should be taken into consideration when selecting a KRAS/BRAF screening assay. This article will review the spectrum of KRAS/BRAF genotype and the impact of KRAS/BRAF mutations on the clinicopathological features and prognosis of patients with CRC, particularly when differentiating between the mutations at KRAS codons 12 and 13. Furthermore, the predictive role of KRAS/BRAF mutations in treatments with anti-EGFR mAb will be verified, focusing on KRAS p.G13D and BRAF mutations.

Socioeconomic status and the risk of colorectal cancer: an analysis of more than a half million adults in the National Institutes of Health-AARP Diet and Health Study

BACKGROUND

No previous prospective US study has examined whether the incidence of colorectal cancer (CRC) is disproportionately high in low socioeconomic status (SES) populations of both men and women. This study examined the relationship between both individual and area-level SES and CRC incidence, overall and by tumor location.

METHODS

Data were obtained from the ongoing prospective National Institutes of Health-AARP Diet and Health Study of persons (50-71 years old) who resided in 6 US states and 2 metropolitan areas at baseline in 1995-1996. Incident CRCs were ascertained from tumor registries through December 2006. SES was measured by self-reported education and census-tract socioeconomic deprivation. Baseline and follow-up questionnaires collected detailed information on individual-level CRC risk factors including family history and health behaviors.

RESULTS

Among 506,488 participants analyzed, 7676 were diagnosed with primary invasive colorectal adenocarcinomas: 44.6% [corrected] in the right colon, 26.7% in the left colon, and 25.9% in the rectum. The overall incidence of CRC was significantly higher among people who had low educational level or lived in low-SES neighborhoods, relative to respective highest-SES groups, even after accounting for other risk factors. These associations were stronger in the rectum than in left or right colon. In the right colon, there were no significant SES differences by either SES measure after accounting for covariates.

CONCLUSIONS

SES, assessed by either individual-level education or neighborhood measures, was associated with risk of CRC even after accounting for other risk factors. The relationship between SES and CRC was strongest in the rectum and weakest in the right colon.

The CpG island methylator phenotype in colorectal cancer: progress and problems

In recent years, attention has focused on the biology and potential clinical importance of the CpG island methylator phenotype (CIMP) in colorectal cancer (CRC). While it is generally well accepted that etiologically and clinically distinct subgroups exist in this disease, a precise definition of CIMP remains to be established. Here, we summarize existing literature that documents the prevalence of CIMP in CRC, with particular attention to the various methods and definitions used to classify a tumor as CIMP positive. Through a systematic review on both case-series and population based studies, we examined only original research articles reporting on sporadic CRC and/or adenomas in unselected cases. Forty-eight papers published between January 1999 and August 2011 met the inclusion criteria. We describe the use of multiple gene panels, marker threshold values, and laboratory techniques which results in a wide range in the prevalence of CIMP. Because there is no universal standard or consensus on quantifying the phenotype, establishing its true prevalence is a challenge. This bottleneck is becoming increasingly evident as molecular pathological epidemiology continues to offer possibilities for clear answers regarding environmental risk factors and disease trends. For the first time, large, unselected series of cases are available for analysis, but comparing populations and pooling data will remain a challenge unless a universal definition of CIMP and a consensus on analysis can be reached, and the primary cause of CIMP identified.

SLC5A8 gene, a transporter of butyrate: a gut flora metabolite, is frequently methylated in African American colon adenomas

Background

Colon cancer is one of the leading causes of cancer related deaths. Its impact on African Americans (AAs) is higher than in the general population both in the incidence and mortality from the disease. Colon cancer aggressiveness in AAs as well as non-frequent check-ups and follow up in this population have been proposed as ways to explain the observed discrepancies. These facts made the detection of early carcinogenesis markers in this population a priority.

Materials and Methods

Here, we analyzed 50 colon adenomas from AA patients for both microsatellite instability (MSI) and the methylation status of SLC5A8 gene. This gene's product is involved in the transport of butyrate that has anti-proliferative properties through its effects on histone acetylation and gene expression. A proteomic analysis to check the expressed histones in adenoma and normal tissues was also performed.

Results

The analyzed samples displayed 82% (n = 41) methylation level of SLC5A8 gene in adenomas. The MSI-H (high) adenoma were about 18% (n = 9) while the rest were mostly MSS (microsatellite stable) with few MSI-L (Low). No association was found between SLC5A8 methylation and the MSI status. Also, there was no association between SLC5A8 methylation and the sex and age of the patients. However, there were more right sided adenomas with SLC5A8 methylation than the left sided ones. The proteomic analysis revealed distinct histone expression profiles between normal and adenoma tissues.

Conclusion

SLC5A8 is highly methylated in AA colon adenomas which points to its potential use as a marker for early detection. The MSI rate is similar to that found in colon cancer tumors in AAs. These findings suggest that both processes stem from the same epigenetic and genetic events occurring at an early stage in colon carcinogenesis in AAs.

IBD-related carcinoma and lymphoma

Patients with inflammatory bowel disease (IBD) have an increased risk of developing colorectal cancer (CRC). Risk factors are extent and severity of colonic inflammation, concurrent primary sclerosing cholangitis, and a positive family history of sporadic CRC. The chromosomal instability, microsatellite instability and hypermethylation pathways form the molecular background of IBD-related carcinogenesis, which is not different from sporadic CRC. The dysplasia-carcinoma sequence of IBD-related colorectal carcinogenesis makes patients suitable for endoscopic surveillance. In the future, new molecular biomarkers and endoscopic techniques may improve early detection of precursor lesions of IBD-related CRC. The potential of aminosalicylates and ursodeoxycholic acid as chemopreventive agents needs to be studied in randomized clinical trials. Patients with IBD who are being treated with thiopurines have a slightly increased risk of developing lymphoproliferative disorders, whereas patients with small bowel Crohn's disease have a high relative risk and a small absolute risk of developing small bowel adenocarcinoma.

Histologic characteristics of non-microsatellite-instable colon adenomas correlate with distinct molecular patterns

Colon carcinogenesis encompasses the stepwise accumulation of genomic aberrations correlated with the transition of aberrant crypt-adenoma-carcinoma. Recent data have revealed that, in addition to the microsatellite-instable phenotype, the chromosome instability pathway, representing four fifth of the colon carcinoma, could be involved in heterogeneous molecular alterations. Our project was aimed at determining the existence of distinct molecular subtypes in 159 non-microsatellite-instable colon polyps and their correlation with histology and dysplasia, using allelotyping, MGMT promoter gene methylation status, and K-RAS mutation analyses. Allelic imbalance, MGMT methylation, and K-RAS mutations arise in 62%, 39%, and 32% of polyps, respectively. Only 14% of polyps had no alterations. A 2-way hierarchical clustering analysis of the allelic imbalances identified subgroups of polyps according to their allelic imbalance frequency and distribution. Not only tubulovillous adenoma but also high-grade adenomas were correlated with high global allelic imbalance frequency (P = .005 and P = .003), with allelic imbalance at microsatellites targeting chromosomes 1, 6, and 9. In conclusion, the data presented in this study show that a large heterogeneity exists in the molecular patterns of alterations in precancerous colon lesions, favoring different modes of tumor initiation. Therefore, molecular alterations correlated with tubulovillous-type and high-grade dysplasia could represent targets identifying predictive factors of progression.

BRAF mutation is a powerful prognostic factor in advanced and recurrent colorectal cancer

Background:

Activating mutation of KRAS and BRAF are focused on as potential prognostic and predictive biomarkers in patients with colorectal cancer (CRC) treated with anti-EGFR therapies. This study investigated the clinicopathological features and prognostic impact of KRAS/BRAF mutation in advanced and recurrent CRC patients.

Method:

Patients with advanced and recurrent CRC treated with systemic chemotherapy (n=229) were analysed for KRAS/BRAF genotypes by cycleave PCR. Prognostic factors associated with survival were identified by univariate and multivariate analyses using the Cox proportional hazards model.

Results:

KRAS and BRAF mutations were present in 34.5% and 6.5% of patients, respectively. BRAF mutated tumours were more likely to develop on the right of the colon, and to be of the poorly differentiated adenocarcinoma or mucinous carcinoma, and peritoneal metastasis. The median overall survival (OS) for BRAF mutation-positive and KRAS 13 mutation-positive patients was 11.0 and 27.7 months, respectively, which was significantly worse than that for patients with wild-type (wt) KRAS and BRAF (40.6 months) (BRAF; HR=4.25, P<0.001, KRAS13; HR=2.03, P=0.024). After adjustment for significant features by multivariate Cox regression analysis, BRAF mutation was associated with poor OS (HR=4.23, P=0.019).

Conclusion:

Presence of mutated BRAF is one of the most powerful prognostic factors for advanced and recurrent CRC. The KRAS13 mutation showed a trend towards poor OS in patients with advanced and recurrent CRC.

Detection of up to 65% of Precancerous Lesions of the Human Colon and Rectum by Mutation Analysis of APC, K-Ras, B-Raf and CTNNB1

In the present study a recently conceived 4-gene marker panel covering the Wnt and Ras-Raf-MEK-MAPK signaling pathways was used to analyze 20 colorectal serrated lesions and 41 colorectal adenoma samples and to determine the percentage of each of the above-mentioned potentially precancerous lesions carrying at least one of the four above-mentioned genes in a mutated form. CTNNB1 and B-Raf were screened by PCR-single-strand conformation polymorphism analysis, K-Ras by restriction fragment length polymorphism analysis and the APC gene mutation cluster region (codons 1243-1567) by direct DNA sequencing. APC mutations were only detected in 10% of the serrated lesions but in 34% of the adenomas. Twenty percent of the serrated lesions and 14% of the adenomas carried a mutated K-Ras. B-Raf was found to be mutated in 50% of the serrated lesions and in 22% of the adenomas. CTNNB1 was altered in 12% of the adenomas, but not in serrated lesions. By using the above gene marker panel it could be shown that 65% of the serrated lesions and 61% of the adenomas carried at least one of the four genes in a mutated form. Based on its excellent performance in detecting mutations in sporadic preneoplastic (in this study) and neoplastic lesions (in a previous study) of the human colon and rectum, this primer combination might also be suited to efficiently and non-invasively detect genetic alterations in stool DNA of patients with early colorectal cancer.

Location in the large bowel influences the APC mutations observed in FAP adenomas

The right colon differs from the left, in embryological origin, luminal environment, and function. In both sporadic colorectal cancer and Familial Adenomatous Polyposis (FAP), polyp density and cancer susceptibility vary markedly by colonic site. Adenomas in FAP have a different mutational spectrum in small intestine versus colon. This study aimed to investigate whether colonic location also influences the APC mutation spectrum in FAP. 127 1-2 mm mildly dysplastic adenomas from 5 patients with a codon 1309 germline mutation, and 41 from 3 patients with mutations proximal to codon 1265, were analysed to assess the frequency of loss of heterozygosity (LOH). We chose polyps from different locations in the colon. Immunohistochemistry for beta-catenin, caspase-3 and Ki-67 was performed to assess Wnt pathway activation, apoptosis and proliferation. In polyps from patients with a 1309 mutation, the frequency of LOH showed a gradient from rectum (highest) to caecum/ascending colon (lowest), but this was not present in patients with proximal germline APC mutations. Crypt-by-crypt analysis confirmed the LOH findings from whole polyps. Beta-catenin and caspase-3 expression showed no significant variation by colonic region, but Ki-67 expression decreased from ascending colon to rectum in tumours and normal tissue. Colonic site alters the mutational spectrum of APC, and crypt cell proliferation. The higher frequency of LOH in rectal polyps from patients with codon 1309 mutations may help to explain their increased polyp burden at this site compared with patients who have other germline APC mutations.

MicroRNA-124a and microRNA-34b/c are frequently methylated in all histological types of colorectal cancer and polyps, and in the adjacent normal mucosa

MicroRNAs (miRs) are a class of small RNAs that regulate gene expression at the post-transcriptional and/or translational level by interacting with their target mRNAs. miRs are down-regulated or up-regulated in various cancer types, triggering abnormal cell differentiation, proliferation and apoptosis. miR-124a and miR-34b/c have been reported to be expressed at lower levels in colorectal cancer (CRC) due to methylation of these genes. The present study aimed to determine the methylation status of miR-124a and miR-34b/c in CRCs and polyps of various histological types, adjacent normal mucosa and ulcerative colitis. The colon cancer cell line study showed an association of the lower expression of miR-124a and miR-34b/c with the methylation of these genes and induction of the expression of these genes with the treatment by 5-aza-2'-deoxycytidine. Among nine different cancer types examined, CRC showed the highest frequency of methylation of miR-124a (cell lines 88% and tissues 99%) and miR-34b/c (cell lines 89% and tissues 93%). Mucinous and non-mucinous CRCs and all the histological types of colorectal polyps showed a high frequency of methylation of miR-124a and miR-34b/c. Notably, methylation of miR-124a (59%) and miR-34b/c (26%) was observed in the adjacent normal mucosa of CRC patients, but not in colonic mucosa from patients without cancer or with ulcerative colitis. The methylation of miR-124a in the adjacent normal mucosa was associated with the microsatellite instability of CRC, while the methylation of miR-34b/c was associated with an older age at diagnosis of CRC. The results showed that the methylation of miR-124a and miR-34b/c occured early in colorectal carcinogenesis and certain CRCs may arise from a field defect defined by the epigenetic inactivation of miRs.

Characteristic methylation profile in CpG island methylator phenotype-negative distal colorectal cancers

Aberrant DNA methylation is involved in colon carcinogenesis. Although the CpG island methylator phenotype (CIMP) is defined as a subset of colorectal cancers (CRCs) with remarkably high levels of DNA methylation, it is not known whether epigenetic processes are also involved in CIMP-negative tumors. We analyzed the DNA methylation profiles of 94 CRCs and their corresponding normal-appearing colonic mucosa with 11 different markers, including the five classical CIMP markers. The CIMP markers were frequently methylated in proximal CRCs (p < 0.01); however, RASSF1A methylation levels were significantly higher in distal CRCs, the majority of which are CIMP-negative (p < 0.05). Similarly, methylation levels of RASSF1A and SFRP1 in the normal-appearing mucosae of distal CRC cases were significantly higher than those in the proximal CRC cases (p < 0.05). They were also positively correlated with age (RASSF1A, p < 0.01; SFRP1, p < 0.01). Microarray-based genome-wide DNA methylation analysis of 18 CRCs revealed that 168 genes and 720 genes were preferentially methylated in CIMP-negative distal CRCs and CIMP-positive CRCs, respectively. Interestingly, more than half of the hypermethylated genes in CIMP-negative distal CRCs were also methylated in the normal-appearing mucosae, indicating that hypermethylation in CIMP-negative distal CRCs is more closely associated with age-related methylation. By contrast, more than 60% of the hypermethylated genes in CIMP-positive proximal CRCs were cancer specific (p < 0.01). These data altogether suggest that CpG island promoters appear to be methylated in different ways depending on location, a finding which may imply the presence of different mechanisms for the acquisition of epigenetic changes during colon tumorigenesis.

Clinicopathological and protein characterization of BRAF- and K-RAS-mutated colorectal cancer and implications for prognosis

Recent evidence highlights the potential prognostic and predictive value of BRAF and K-RAS gene alterations in patients with colorectal cancer. However, a comprehensive evaluation of BRAF and K-RAS mutations and their specific clinicopathological features, histomorphological presentation and effect on protein expression have not been systematically analyzed. The aim of this study was to characterize the clinicopathological, histomorphological and protein expression profiles of BRAF- and K-RAS-mutated colorectal cancers and determine their impact on patient survival. Molecular analysis for microsatellite instability (MSI), K-RAS and BRAF was carried out on paraffin-embedded samples from 404 patients with primary colorectal cancer. Using tissue microarrays, 36 tumor-associated and 14 lymphocyte/inflammatory-associated markers were evaluated by immunohistochemistry. BRAF mutation was associated with right-sided tumor location (p < 0.001), higher tumor grade (p = 0.029), absence of peritumoral lymphocytic inflammation (p = 0.026) and MSI-H (p < 0.001). In right-sided tumors, loss of CDX2 expression was observed in 23 of 24 cases (95.8%). BRAF mutation was a poor prognostic indicator in patients with right-sided disease (p = 0.01). This result was maintained in multivariable analysis (p < 0.001; HR = 2.82; 95% CI: 1.5-5.5) with pT, pN and vascular invasion and independent of CDX2 expression. K-RAS mutation, in contrast, was not associated with any of the features analyzed. BRAF gene mutation is an adverse prognostic factor in right-sided colon cancer patients independent of MSI status and, moreover, in patients with lymph node-negative disease. These results indicate that molecular analysis for BRAF may be a useful biomarker for identifying patients with right-sided colon cancer with poor outcome who may benefit from a more individualized course of therapy.

Dietary, lifestyle and clinicopathological factors associated with BRAF and K-ras mutations arising in distinct subsets of colorectal cancers in the EPIC Norfolk study

BACKGROUND

BRAF and K-ras proto-oncogenes encode components of the ERK signalling pathway and are frequently mutated in colorectal cancer. This study investigates the associations between BRAF and K-ras mutations and clinicopathological, lifestyle and dietary factors in colorectal cancers.

METHODS

186 adenocarcinomas and 16 adenomas from the EPIC Norfolk study were tested for BRAF and K-ras mutations. Diet and lifestyle data were collected prospectively using seven day food diaries.

RESULTS

BRAF V600E mutation was found in 15.6% of colorectal cancers but at higher frequencies in cancers with proximal location, poor differentiation and microsatellite instability (MSI) (all p < 0.001). K-ras mutation (mostly in codons 12 and 13) was found in 22.0% of colorectal cancers but at higher frequencies in cancers of more advanced Dukes' stage (p = 0.001), microsatellite stable (MSS) status (p = 0.002) and in individuals with lower blood high-density lipoprotein concentrations (p = 0.04). Analysis of dietary factors demonstrated no link between BRAF mutation and any specific dietary constituent, however, K-ras mutation was found at higher frequencies in individuals with higher white meat consumption (p < 0.001). Further analysis of specific mutation type demonstrated that G to A transitions in K-ras were observed at higher frequencies in individuals consuming lower amounts of fruit (p = 0.02).

CONCLUSION

These data support the model of BRAF and K-ras mutations arising in distinct colorectal cancer subsets associated with different clinicopathological and dietary factors, acting as mutually exclusive mechanisms of activation of the same signalling pathway.

The role of the CpG island methylator phenotype in colorectal cancer prognosis depends on microsatellite instability screening status

PURPOSE

The aim of this study was to relate the CpG island methylator phenotype (CIMP; characterized by extensive promoter hypermethylation) to cancer-specific survival in colorectal cancer, taking into consideration relevant clinicopathologic factors, such as microsatellite instability (MSI) screening status and the BRAF V600E mutation.

EXPERIMENTAL DESIGN

Archival tumor samples from 190 patients from the Northern Sweden Health and Disease Study (NSHDS) and 414 patients from the Colorectal Cancer in Umeå Study (CRUMS), including 574 with cancer-specific survival data, were analyzed for an eight-gene CIMP panel using quantitative real-time PCR (MethyLight). MSI screening status was assessed by immunohistochemistry.

RESULTS

CIMP-low patients had a shorter cancer-specific survival compared with CIMP-negative patients (multivariate hazard ratio in NSHDS, 2.01; 95% confidence interval, 1.20-3.37; multivariate hazard ratio in CRUMS, 1.48; 95% confidence interval, 1.00-2.22). This result was similar in subgroups based on MSI screening status and was statistically significant in microsatellite stable (MSS) tumors in NSHDS. For CIMP-high patients, a shorter cancer-specific survival compared with CIMP-negative patients was observed in the MSS subgroup. Statistical significance was lost after adjusting for the BRAF mutation, but the main findings were generally unaffected.

CONCLUSIONS

In this study, we found a poor prognosis in CIMP-low patients regardless of MSI screening status, and in CIMP-high patients with MSS. Although not consistently statistically significant, these results were consistent in two separate patient groups and emphasize the potential importance of CIMP and MSI status in colorectal cancer research.