Isocitrate dehydrogenase 1 R132C mutation occurs exclusively in microsatellite stable colorectal cancers with the CpG island methylator phenotype

The CpG Island Methylator Phenotype (CIMP) is fundamental to an important subset of colorectal cancer; however, its cause is unknown. CIMP is associated with microsatellite instability but is also found in BRAF mutant microsatellite stable cancers that are associated with poor prognosis. The isocitrate dehydrogenase 1 (IDH1) gene causes CIMP in glioma due to an activating mutation that produces the 2-hydroxyglutarate oncometabolite. We therefore examined IDH1 alteration as a potential cause of CIMP in colorectal cancer. The IDH1 mutational hotspot was screened in 86 CIMP-positive and 80 CIMP-negative cancers. The entire coding sequence was examined in 81 CIMP-positive colorectal cancers. Forty-seven cancers varying by CIMP-status and IDH1 mutation status were examined using Illumina 450K DNA methylation microarrays. The R132C IDH1 mutation was detected in 4/166 cancers. All IDH1 mutations were in CIMP cancers that were BRAF mutant and microsatellite stable (4/45, 8.9%). Unsupervised hierarchical cluster analysis identified an IDH1 mutation-like methylation signature in approximately half of the CIMP-positive cancers. IDH1 mutation appears to cause CIMP in a small proportion of BRAF mutant, microsatellite stable colorectal cancers. This study provides a precedent that a single gene mutation may cause CIMP in colorectal cancer, and that this will be associated with a specific epigenetic signature and clinicopathological features.     

Analysis of the Association between CIMP and BRAFV600E in Colorectal Cancer by DNA Methylation Profiling

A CpG island methylator phenotype (CIMP) is displayed by a distinct subset of colorectal cancers with a high frequency of DNA hypermethylation in a specific group of CpG islands. Recent studies have shown that an activating mutation of BRAF (BRAF^V600E) is tightly associated with CIMP, raising the question of whether BRAF^V600E plays a causal role in the development of CIMP or whether CIMP provides a favorable environment for the acquisition of BRAF^V600E. We employed Illumina GoldenGate DNA methylation technology, which interrogates 1,505 CpG sites in 807 different genes, to further study this association. We first examined whether expression of BRAF^V600E causes DNA hypermethylation by stably expressing BRAF^V600E in the CIMP-negative, BRAF wild-type COLO 320DM colorectal cancer cell line. We determined 100 CIMP-associated CpG sites and examined changes in DNA methylation in eight stably transfected clones over multiple passages. We found that BRAF^V600E is not sufficient to induce CIMP in our system. Secondly, considering the alternative possibility, we identified genes whose DNA hypermethylation was closely linked to BRAF^V600E and CIMP in 235 primary colorectal tumors. Interestingly, genes that showed the most significant link include those that mediate various signaling pathways implicated in colorectal tumorigenesis, such as BMP3 and BMP6 (BMP signaling), EPHA3, KIT, and FLT1 (receptor tyrosine kinases) and SMO (Hedgehog signaling). Furthermore, we identified CIMP-dependent DNA hypermethylation of IGFBP7, which has been shown to mediate BRAF^V600E-induced cellular senescence and apoptosis. Promoter DNA hypermethylation of IGFBP7 was associated with silencing of the gene. CIMP-specific inactivation of BRAF^V600E-induced senescence and apoptosis pathways by IGFBP7 DNA hypermethylation might create a favorable context for the acquisition of BRAF^V600E in CIMP+ colorectal cancer. Our data will be useful for future investigations toward understanding CIMP in colorectal cancer and gaining insights into the role of aberrant DNA hypermethylation in colorectal tumorigenesis.     

CpG island methylator phenotype and its association with malignancy in sporadic duodenal adenomas

CpG island methylator phenotype (CIMP) has been found in multiple precancerous and cancerous lesions, including colorectal adenomas, colorectal cancers, and duodenal adenocarcinomas. There are no reports in the literature of a relationship between CIMP status and clinicopathologic features of sporadic duodenal adenomas. This study sought to elucidate the role of methylation in duodenal adenomas and correlate it with KRAS and BRAF mutations. CIMP+ (with more than 2 markers methylated) was seen in 33.3% of duodenal adenomas; 61% of these CIMP+ adenomas were CIMP-high (with more than 3 markers methylated). Furthermore, CIMP+ status significantly correlated with older age of patients, larger size and villous type of tumor, coexistent dysplasia and periampullary location. MLH1 methylation was seen in 11.1% of duodenal adenomas and was significantly associated with CIMP+ tumors, while p16 methylation was an infrequent event. KRAS mutations were frequent and seen in 26.3% of adenomas; however, no BRAF mutations were detected. Furthermore, CIMP-high status was associated with larger size and villous type of tumor and race (non-white). These results suggest that CIMP+ duodenal adenomas may have a higher risk for developing malignancy and may require more aggressive management and surveillance.     

Chromosomal Instability in BRAF Mutant,Microsatellite Stable Colorectal Cancers

The BRAF oncogene is mutated in 15% of sporadic colorectal cancers. Approximately half of these BRAF mutant cancers demonstrate frequent frameshift mutations termed microsatellite instability (MSI), but are diploid and chromosomally stable. BRAF wild type cancers are typically microsatellite stable (MSS) and instead acquire chromosomal instability (CIN). In these cancers, CIN is associated with a poor outcome. BRAF mutant cancers that are MSS, typically present at an advanced stage and have a particularly poor prognosis. We have previously demonstrated clinical and molecular similarities between MSS cancers with or without a BRAF mutation, and therefore hypothesised that CIN may also be frequent in BRAF mutant/MSS cancers. BRAF mutant/MSS (n = 60), and BRAF wild type/MSS CRCs (n = 90) were investigated for CIN using loss of heterozygosity analysis over twelve loci encompassing chromosomal regions 5q, 8p, 17p and 18q. CIN was frequent in BRAF mutant/MSS cancers (41/57, 72%), which was comparable to the rate found in BRAF wild type/MSS cancers (74/90, 82%). The greatest loss in BRAF mutant/MSS cancers occurred at 8p (26/44, 59%), and the least at 5q (19/49, 39%). CIN in BRAF mutant/MSS cancers correlated with advanced stage (AJCC III/IV: 15/17, 88%; p = 0.02); showed high rates of co-occurrence with the CpG Island Methylator Phenotype (17/23, 74%); and CIN at 18q and 8p associated with worse survival (p = 0.02, p<0.05). This study demonstrates that CIN commonly occurs in advanced BRAF mutant/MSS colorectal cancers where it may contribute to poorer survival, and further highlights molecular similarities occurring between these and BRAF wild type cancers.     

Comprehensive Biostatistical Analysis of CpG Island Methylator Phenotype in Colorectal Cancer Using a Large Population-Based Sample

Background

The CpG island methylator phenotype (CIMP) is a distinct phenotype associated with microsatellite instability (MSI) and BRAF mutation in colon cancer. Recent investigations have selected 5 promoters (CACNA1G, IGF2, NEUROG1, RUNX3 and SOCS1) as surrogate markers for CIMP-high. However, no study has comprehensively evaluated an expanded set of methylation markers (including these 5 markers) using a large number of tumors, or deciphered the complex clinical and molecular associations with CIMP-high determined by the validated marker panel.

Metholodology/Principal Findings

DNA methylation at 16 CpG islands [the above 5 plus CDKN2A (p16), CHFR, CRABP1, HIC1, IGFBP3, MGMT, MINT1, MINT31, MLH1, p14 (CDKN2A/ARF) and WRN] was quantified in 904 colorectal cancers by real-time PCR (MethyLight). In unsupervised hierarchical clustering analysis, the 5 markers (CACNA1G, IGF2, NEUROG1, RUNX3 and SOCS1), CDKN2A, CRABP1, MINT31, MLH1, p14 and WRN were generally clustered with each other and with MSI and BRAF mutation. KRAS mutation was not clustered with any methylation marker, suggesting its association with a random methylation pattern in CIMP-low tumors. Utilizing the validated CIMP marker panel (including the 5 markers), multivariate logistic regression demonstrated that CIMP-high was independently associated with older age, proximal location, poor differentiation, MSI-high, BRAF mutation, and inversely with LINE-1 hypomethylation and β-catenin (CTNNB1) activation. Mucinous feature, signet ring cells, and p53-negativity were associated with CIMP-high in only univariate analysis. In stratified analyses, the relations of CIMP-high with poor differentiation, KRAS mutation and LINE-1 hypomethylation significantly differed according to MSI status.

Conclusions

Our study provides valuable data for standardization of the use of CIMP-high-specific methylation markers. CIMP-high is independently associated with clinical and key molecular features in colorectal cancer. Our data also suggest that KRAS mutation is related with a random CpG island methylation pattern which may lead to CIMP-low tumors.     

CpG island methylator phenotype and its association with malignancy in sporadic duodenal adenomas

CpG island methylator phenotype (CIMP) has been found in multiple precancerous and cancerous lesions, including colorectal adenomas, colorectal cancers, and duodenal adenocarcinomas. There are no reports in the literature of a relationship between CIMP status and clinicopathologic features of sporadic duodenal adenomas. This study sought to elucidate the role of methylation in duodenal adenomas and correlate it with KRAS and BRAF mutations. CIMP+ (with more than 2 markers methylated) was seen in 33.3% of duodenal adenomas; 61% of these CIMP+ adenomas were CIMP-high (with more than 3 markers methylated). Furthermore, CIMP+ status significantly correlated with older age of patients, larger size and villous type of tumor, coexistent dysplasia and periampullary location. MLH1 methylation was seen in 11.1% of duodenal adenomas and was significantly associated with CIMP+ tumors, while p16 methylation was an infrequent event. KRAS mutations were frequent and seen in 26.3% of adenomas; however, no BRAF mutations were detected. Furthermore, CIMP-high status was associated with larger size and villous type of tumor and race (non-white). These results suggest that CIMP+ duodenal adenomas may have a higher risk for developing malignancy and may require more aggressive management and surveillance.     

TGFBR2 and BAX mononucleotide tract mutations, microsatellite instability, and prognosis in 1072 colorectal cancers

Background

Mononucleotide tracts in the coding regions of the TGFBR2 and BAX genes are commonly mutated in microsatellite instability-high (MSI-high) colon cancers. The receptor TGFBR2 plays an important role in the TGFB1 (transforming growth factor-β, TGF-β) signaling pathway, and BAX plays a key role in apoptosis. However, a role of TGFBR2 or BAX mononucleotide mutation in colorectal cancer as a prognostic biomarker remains uncertain.

Methodology/Principal Findings

We utilized a database of 1072 rectal and colon cancers in two prospective cohort studies (the Nurses'' Health Study and the Health Professionals Follow-up Study). Cox proportional hazards model was used to compute mortality hazard ratio (HR), adjusted for clinical, pathological and molecular features including the CpG island methylator phenotype (CIMP), LINE-1 methylation, and KRAS, BRAF and PIK3CA mutations. MSI-high was observed in 15% (162/1072) of all colorectal cancers. TGFBR2 and BAX mononucleotide mutations were detected in 74% (117/159) and 30% (48/158) of MSI-high tumors, respectively. In Kaplan-Meier analysis as well as univariate and multivariate Cox regression analyses, compared to microsatellite stable (MSS)/MSI-low cases, MSI-high cases were associated with superior colorectal cancer-specific survival [adjusted HR, 0.34; 95% confidence interval (CI), 0.20–0.57] regardless of TGFBR2 or BAX mutation status. Among MSI-high tumors, TGFBR2 mononucleotide mutation was associated with CIMP-high independent of other variables [multivariate odds ratio, 3.57; 95% CI, 1.66–7.66; p = 0.0011].

Conclusions

TGFBR2 or BAX mononucleotide mutations are not associated with the patient survival outcome in MSI-high colorectal cancer. Our data do not support those mutations as prognostic biomarkers (beyond MSI) in colorectal carcinoma.     

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.     

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, ΔDNMT3B ?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 ΔDNMT3B ?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.     

B vitamins, methionine and alcohol intake and risk of colon cancer in relation to BRAF mutation and CpG island methylator phenotype (CIMP)

Background

One-carbon metabolism appears to play an important role in DNA methylation reaction. Evidence suggests that a low intake of B vitamins or high alcohol consumption increases colorectal cancer risk. How one-carbon nutrients affect the CpG island methylator phenotype (CIMP) or BRAF mutation status in colon cancer remains uncertain.

Methods

Utilizing incident colon cancers in a large prospective cohort of women (the Nurses'' Health Study), we determined BRAF status (N = 386) and CIMP status (N = 375) by 8 CIMP-specific markers [CACNA1G, CDKN2A (p16), CRABP1, IGF2, MLH1, NEUROG1, RUNX3, and SOCS1], and 8 other CpG islands (CHFR, HIC1, IGFBP3, MGMT, MINT-1, MINT-31, p14, and WRN). We examined the relationship between intake of one-carbon nutrients and alcohol and colon cancer risk, by BRAF mutation or CIMP status.

Results

Higher folate intake was associated with a trend towards low risk of CIMP-low/0 tumors [total folate intake ≥400 µg/day vs. <200 µg/day; the multivariate relative risk = 0.73; 95% CI = 0.53–1.02], whereas total folate intake had no influence on CIMP-high tumor risks (P_{heterogeneity} = 0.73). Neither vitamin B₆, methionine or alcohol intake appeared to differentially influence risks for CIMP-high and CIMP-low/0 tumors. Using the 16-marker CIMP panel did not substantially alter our results. B vitamins, methionine or alcohol intake did not affect colon cancer risk differentially by BRAF status.

Conclusions

This molecular pathological epidemiology study suggests that low level intake of folate may be associated with an increased risk of CIMP-low/0 colon tumors, but not that of CIMP-high tumors. However, the difference between CIMP-high and CIMP-low/0 cancer risks was not statistically significant, and additional studies are necessary to confirm these observations.     

The CpG island methylator phenotype correlates with long-range epigenetic silencing in colorectal cancer

The CpG island methylator phenotype (CIMP), characterized by an exceptionally high frequency of methylation of discrete CpG islands, is observed in 18% to 25% of sporadic colorectal cancers. Another hypermethylation pattern found in colorectal cancers, termed long-range epigenetic silencing, is associated with DNA/histone methylation in three distinct gene clusters at chromosome 2q14.2, showing that DNA hypermethylation can span larger chromosomal domains and lead to the silencing of flanking, unmethylated genes. We investigated whether these two phenotypes are interrelated in colorectal cancers. The CIMP status of 148 sporadic colorectal cancers was determined by methylation-specific PCR. We determined the BRAF V600E mutation by mutant allele-specific PCR amplification. The methylation status of the MLH1 gene and of three CpG islands (EN1, SCTR, and INHBB), corresponding to three distinct clusters along 2q14.2, was determined by methylation-specific PCR. The average number of sites showing methylation in CIMP+ tumors was 2.21, compared with 1.22 for CIMP- individuals, and this difference was highly significant (P = 3.6 x 10(-8), Mann-Whitney test). Moreover, all CIMP+ tumors showed hypermethylation of at least one of these loci, in contrast to CIMP- tumors, where 18 (16%) samples remained unmethylated. The mean number of simultaneously hypermethylated CpG islands at 2q14.2 differs significantly between CIMP- and CIMP+ tumors, suggesting varying effects of domain silencing in this region. Given that the number of hypermethylated loci at 2q14.2 likely affects the range of silenced flanking genes, high frequency of simultaneous hypermethylation of three CpG islands (EN1, SCTR, and INHBB) may have potential influence on specific characteristics of CIMP+ colorectal cancers.     

Oncogenic BRAF mutation induces DNA methylation changes in a murine model for human serrated colorectal neoplasia

Colorectal cancer is a major cause of cancer death and approximately 20% arises within serrated polyps, which are under-recognized and poorly understood. Human serrated colorectal polyps frequently exhibit both oncogenic BRAF mutation and widespread DNA methylation changes, which are important in silencing genes restraining neoplastic progression. Here, we investigated whether in vivo induction of mutant Braf is sufficient to result in coordinated promoter methylation changes for multiple cancer-related genes. The Braf^V637E mutation was induced in murine intestine on an FVB;C57BL/6J background and assessed for morphological and DNA methylation changes at multiple time points from 10 days to 14 months. Extensive intestinal hyperplasia developed by 10 days post-induction of the mutation. By 8 months, most mice had murine serrated adenomas with dysplasia and invasive cancer developed in 40% of mice by 14 months. From 5 months onwards, Braf mutant mice showed extensive, gene-specific increases in DNA methylation even in hyperplastic mucosa without lesions. This demonstrates that persistent oncogenic Braf signaling is sufficient to induce widespread DNA methylation changes. This occurs over an extended period of time, mimicking the long latency followed by rapid progression of human serrated neoplasia. This study establishes for the first time that DNA methylation arises slowly in direct response to prolonged oncogenic Braf signaling in serrated polyps; this finding has implications both for chemoprevention and for understanding the origin of DNA hypermethylation in cancer generally.     

Correlation between BRAF mutation and promoter methylation of TIMP3, RARβ2 and RASSF1A in thyroid cancer

Our aim was to comprehensively analyze promoter hypermethylation of a panel of novel and known methylation markers for thyroid neoplasms and to establish their relationship with BRAF mutation and clinicopathologic parameters of thyroid cancer. A cohort of thyroid tumors, consisting of 44 cancers and 44 benign thyroid lesions, as well as 15 samples of adjacent normal thyroid tissue, was evaluated for BRAF mutation and promoter hypermethylation. Genes for quantitative methylation specific PCR (QMSP) were selected by a candidate gene approach. Twenty-two genes were tested: TSHR, RASSF1A, RARβ2, DAPK, hMLH1, ATM, S100, p16, CTNNB1, GSTP1, CALCA, TIMP3, TGFßR2, THBS1, MINT1, CTNNB1, MT1G, PAK3, NISCH, DCC, AIM1 and KIF1A. The PCR-based “mutector assay” was used to detect BRAF mutation. All p values reported are two sided. Considerable overlap was seen in the methylation markers among the different tissue groups. Significantly higher methylation frequency and level were observed for KIF1A and RARß2 in cancer samples compared with benign tumors. A negative correlation between BRAF mutation and RASSF1A methylation, and a positive correlation with RARß2 methylation were observed in accordance with previous results. In addition, positive correlation with TIMP3 and a marginal correlation with DCC methylation were observed. The present study constitutes a comprehensive promoter methylation profile of thyroid neoplasia and shows that results must be analyzed in a tissue-specific manner to identify clinically useful methylation markers. Integration of genetic and epigenetic changes in thyroid cancer will help identify relevant biologic pathways that drive its development.     

Clinical Significance of MLH1 Methylation and CpG Island Methylator Phenotype as Prognostic Markers in Patients with Gastric Cancer

Background

To improve the outcome of patients suffering from gastric cancer, a better understanding of underlying genetic and epigenetic events in this malignancy is required. Although CpG island methylator phenotype (CIMP) and microsatellite instability (MSI) have been shown to play pivotal roles in gastric cancer pathogenesis, the clinical significance of these events on survival outcomes in patients with gastric cancer remains unknown.

Methods

This study included a patient cohort with pathologically confirmed gastric cancer who had surgical resections. A cohort of 68 gastric cancers was analyzed. CIMP and MSI statuses were determined by analyzing promoter CpG island methylation status of 28 genes/loci, and genomic instability at 10 microsatellite markers, respectively. A Cox’s proportional hazards model was performed for multivariate analysis including age, stage, tumor differentiation, KRAS mutation status, and combined CIMP/MLH1 methylation status in relation to overall survival (OS).

Results

By multivariate analysis, longer OS was significantly correlated with lower pathologic stage (P = 0.0088), better tumor differentiation (P = 0.0267) and CIMP-high and MLH1 3'' methylated status (P = 0.0312). Stratification of CIMP status with regards to MLH1 methylation status further enabled prediction of gastric cancer prognosis.

Conclusions

CIMP and/or MLH1 methylation status may have a potential to be prognostic biomarkers for patients with gastric cancer.     

<Emphasis Type="Italic">PIK3CA</Emphasis> mutations in <Emphasis Type="Italic">KRAS</Emphasis> and <Emphasis Type="Italic">BRAF</Emphasis> wild type colorectal cancer patients. A study of Spanish population

The objective of the work was to study PIK3CA mutations in wild type KRAS and BRAF colorectal cancer. Clinicopathological data and paraffin-embedded specimens were collected on 73 patients who underwent colorectal resections at General Yagüe Hospital in Burgos. KRAS, BRAF and PIK3CA status were analyzed by real-time PCR in all patients. PIK3CA mutations were present in 8.22% of wild type KRAS and BRAF colorectal cancers. The most frequent mutation is E545K/D in exon 9 which represents 83.3% of all mutations. By contrast, we did not found any tumour harbouring H1047R mutation in exon 20. Among the patients who undergo a curative resection of colorectal cancer, PIK3CA mutation is present in an important percentage of KRAS and BRAF wild type tumours. PIK3CA mutation may be considered as it could be a hypothetic reason to be not responder to anti-EGFR antibodies.     

Toward a comprehensive and systematic methylome signature in colorectal cancers

CpG Island Methylator Phenotype (CIMP) is one of the underlying mechanisms in colorectal cancer (CRC). This study aimed to define a methylome signature in CRC through a methylation microarray analysis and a compilation of promising CIMP markers from the literature. Illumina HumanMethylation27 (IHM27) array data was generated and analyzed based on statistical differences in methylation data (1st approach) or based on overall differences in methylation percentages using lower 95% CI (2nd approach). Pyrosequencing was performed for the validation of nine genes. A meta-analysis was used to identify CIMP and non-CIMP markers that were hypermethylated in CRC but did not yet make it to the CIMP genes’ list. Our 1st approach for array data analysis demonstrated the limitations in selecting genes for further validation, highlighting the need for the 2nd bioinformatics approach to adequately select genes with differential aberrant methylation. A more comprehensive list, which included non-CIMP genes, such as APC, EVL, CD109, PTEN, TWIST1, DCC, PTPRD, SFRP1, ICAM5, RASSF1A, EYA4, 30ST2, LAMA1, KCNQ5, ADHEF1, and TFPI2, was established. Array data are useful to categorize and cluster colonic lesions based on their global methylation profiles; however, its usefulness in identifying robust methylation markers is limited and rely on the data analysis method. We have identified 16 non-CIMP-panel genes for which we provide rationale for inclusion in a more comprehensive characterization of CIMP+ CRCs. The identification of a definitive list for methylome specific genes in CRC will contribute to better clinical management of CRC patients.     

The Prognostic Value of BRAF Mutation in Colorectal Cancer and Melanoma: A Systematic Review and Meta-Analysis

Background

Mutation of BRAF is a predominant event in cancers with poor prognosis such as melanoma and colorectal cancer. BRAF mutation leads to a constitutive activation of mitogen activated protein kinase pathway which is essential for cell proliferation and tumor progression. Despite tremendous efforts made to target BRAF for cancer treatment, the correlation between BRAF mutation and patient survival is still a matter of controversy.

Methods/Principal Findings

Clinical studies on the correlation between BRAF mutation and patient survival were retrieved from MEDLINE and EMBASE databases between June 2002 and December 2011. One hundred twenty relevant full text studies were categorized based on study design and cancer type. Publication bias was evaluated for each category and pooled hazard ratio (HR) with 95% confidence interval (CI) was calculated using random or fixed effect meta-analysis based on the percentage of heterogeneity. Twenty six studies on colorectal cancer (11,773 patients) and four studies on melanoma (674 patients) were included in our final meta-analysis. The average prevalence of BRAF mutation was 9.6% in colorectal cancer, and 47.8% in melanoma reports. We found that BRAF mutation increases the risk of mortality in colorectal cancer patients for more than two times; HR = 2.25 (95% CI, 1.82–2.83). In addition, we revealed that BRAF mutation also increases the risk of mortality in melanoma patients by 1.7 times (95% CI, 1.37–2.12).

Conclusions

We revealed that BRAF mutation is an absolute risk factor for patient survival in colorectal cancer and melanoma.     

<Emphasis Type="Italic">BRAF</Emphasis> V600E mutation and resistance to anti-EGFR monoclonal antibodies in patients with metastatic colorectal cancer: a meta-analysis

Epidemiologic studies have evaluated the association between BRAF mutations and resistance to the treatment of anti-EGFR monoclonal antibodies (MoAb) in patients with metastatic colorectal cancer (mCRC). However, the results are still inconclusive. To derive a more precise estimation of the relationship, we performed this meta-analysis. A total of 11 studies were included in the final meta-analysis. There were seven studies for unselected mCRC patients and four studies for patients with wild type KRAS mCRC. Among unselected mCRC patients, BRAF V600E mutation was detected in 48 of 546 primary tumors (8.8%). The objective response rate (ORR) of patients with mutant BRAF was 29.2% (14/48), whereas the ORR of patients with wild-type BRAF was 33.5% (158/472).The overall RR for ORR of mutant BRAF patients over wild-type BRAF patients was 0.86 (95% CI = 0.57–1.30; P = 0.48). For patients with KRAS wild-type mCRC, BRAF V600E mutation was detected in 40 of 376 primary tumors (10.6%). The ORR of patients with mutant BRAF was 0.0% (0/40), whereas the ORR of patients with wild-type BRAF was 36.3% (122/336). The pooled RR of mutant BRAF patients over wild-type BRAF patients was 0.14 (95% CI = 0.04–0.53; P = 0.004). In conclusion, this meta-analysis provides evidence that BRAF V600E mutation is associated with lack of response in wild-type KRAS mCRC treated with anti-EGFR MoAbs. BRAF mutation may be used as an additional biomarker for the selection of mCRC patients who might benefit from anti-EGFR MoAbs therapy.     

A modified screening strategy for Lynch syndrome among MLH1-deficient CRCs: Analysis from consecutive Chinese patients in a single center

BackgroundThe low prevalence of the BRAF V600E mutation in colorectal cancers (CRCs) in Chinese populations has stimulated concern about the efficacy of BRAF mutation analysis for Lynch syndrome (LS) screening.MethodsIn total, 169 of 4104 consecutive CRC patients with absent MLH1 staining were analyzed to compare the utility of the BRAF V600E mutation testing with MLH1 promoter methylation analysis in the Chinese population. Germline genetic testing was performed in patients with wild-type BRAF/methylated MLH1.ResultsCompared with BRAF genotyping, the use of MLH1 methylation testing alone to evaluate patients with MLH1 deficiency reduced referral rates for germline testing by 1.8-fold (82.8% vs. 47.1%). However, 6 patients harboring MLH1 promoter methylation were verified to have LS through germline genetic testing. It is notable that all 6 patients had a family history of CRC in at least 1 first-degree relative (FDR) or second-degree relative (SDR). The combination of MLH1 promoter methylation analysis and a family history of CRC could preclude significantly more patients from germline genetic testing than from BRAF mutation testing alone (45.5% vs. 17.2%, p<0.001) and decrease the number of misdiagnosed LS patients with MLH1 promoter methylation.ConclusionThe combination of a family history of CRC with MLH1 promoter methylation analysis showed better performance than BRAF mutation testing in the selection of patients in the Chinese population for germline genetic testing.