An EZH2 polymorphism is associated with clinical outcome in metastatic colorectal cancer patients

A genetic variant in the immune-related gene ERAP1 affects colorectal cancer prognosis

BACKGROUND

Findings on the association of genetic factors and colorectal cancer (CRC) survival are limited and inconsistent, and revealing the mechanism underlying their prognostic roles is of great importance. This study aimed to explore the relationship between functional genetic variations and the prognosis of CRC and further reveal the possible mechanism.

METHODS

We first systematically performed expression quantitative trait locus (eQTL) analysis using The Cancer Genome Atlas (TCGA) dataset. Then, the Kaplan-Meier analysis was used to filter out the survival-related eQTL target genes of CRC patients in two public datasets (TCGA and GSE39582 dataset from the Gene Expression Omnibus database). The seven most potentially functional eQTL single nucleotide polymorphisms (SNPs) associated with six survival-related eQTL target genes were genotyped in 907 Chinese CRC patients with clinical prognosis data. The regulatory mechanism of the survival-related SNP was further confirmed by functional experiments.

RESULTS

The rs71630754 regulating the expression of endoplasmic reticulum aminopeptidase 1 ( ERAP1 ) was significantly associated with the prognosis of CRC (additive model, hazard ratio [HR]: 1.43, 95% confidence interval [CI]: 1.08-1.88, P = 0.012). The results of dual-luciferase reporter assay and electrophoretic mobility shift assay showed that the A allele of the rs71630754 could increase the binding of transcription factor 3 (TCF3) and subsequently reduce the expression of ERAP1 . The results of bioinformatic analysis showed that lower expression of ERAP1 could affect the tumor immune microenvironment and was significantly associated with severe survival outcomes.

CONCLUSION

The rs71630754 could influence the prognosis of CRC patients by regulating the expression of the immune-related gene ERAP1 .

TRIAL REGISTRATION

No. NCT00454519 ( https://clinicaltrials.gov/ ).

EZH2 Expression and Survival for ER+/tamoxifen Treated Breast Cancer Patients with rs2302427 C>G: A Novel Prognostic and Risk Predictive Biomarker

BACKGROUND AND OBJECTIVES

Overexpression of the EZH2 gene silences several genes involved in DNA repair, cell-cell adhesion, and tumor suppressor genes, resulting in the development of several types of cancers. In the present study, a genetic polymorphism analysis was performed by selecting three SNPs (rs.2302427C>G, rs.3757441C>T, and rs.6950683T>C) of the EZH2 gene based on our previous in silico studies.

METHODS

A total of 250 breast cancer patients and 250 healthy individuals were recruited for the study. Patients with pre-operative breast cancer with different clinical-pathological variables and age-matched healthy women were recruited for the EZH2 gene expression analysis.

RESULTS

The genetic polymorphism analysis revealed two SNPs (rs.2302427C>G and rs.6950683T>C) of the three studied SNPs of the EZH2 gene have a protective role in all three genetic models. The haplotype analysis predicted that two haplotypes ACGT and ACGC were significantly associated with a lower risk of breast cancer.

INTERPRETATION AND CONCLUSIONS

Three significant findings of the SNP rs.2302427C>G (Asp193His) i.e., protective role against breast cancer, survival advantage in ER+/tamoxifen treated breast cancer patients, and decreased expression due to the presence of mutant GG genotype, suggests considering it as an important prognostic biomarker for a good survival outcome of breast cancer patients treated with ER+/tamoxifen. Compared with other studies, the other SNP rs.3757441T>C was observed to have a protective effect in breast cancer biology but plays an antagonistic role in colorectal cancer (CRC) biology. To our knowledge, this is the first detailed study on computationally validated EZH2 SNPs in breast cancer.

The role of epigenetic modifications in Colorectal Cancer Metastasis

Distant metastasis is the major contributor to the high mortality rate of colorectal cancer (CRC). To overcome the poor prognosis caused by distant metastasis, the mechanisms of CRC metastasis should be further explored. Epigenetic events are the main mediators of gene regulation and further affect tumor progression. Recent studies have found that some epigenetic enzymes are often dysregulated or mutated in multiple tumor types, which prompted us to study the roles of these enzymes in CRC metastasis. In this review, we summarized the alteration of enzymes related to various modifications, including histone modification, nonhistone modification, DNA methylation, and RNA methylation, and their epigenetic mechanisms during the progression of CRC metastasis. Existing data suggest that targeting epigenetic enzymes is a promising strategy for the treatment of CRC metastasis.

Targeting epigenetic regulators for cancer therapy: mechanisms and advances in clinical trials

Epigenetic alternations concern heritable yet reversible changes in histone or DNA modifications that regulate gene activity beyond the underlying sequence. Epigenetic dysregulation is often linked to human disease, notably cancer. With the development of various drugs targeting epigenetic regulators, epigenetic-targeted therapy has been applied in the treatment of hematological malignancies and has exhibited viable therapeutic potential for solid tumors in preclinical and clinical trials. In this review, we summarize the aberrant functions of enzymes in DNA methylation, histone acetylation and histone methylation during tumor progression and highlight the development of inhibitors of or drugs targeted at epigenetic enzymes.

Epigenetic regulation of cancer biology and anti-tumor immunity by EZH2

Polycomb group proteins regulate chromatin structure and have an important regulatory role on gene expression in various cell types. Two polycomb group complexes (Polycomb repressive complex 1 (PRC1) and 2 (PRC2)) have been identified in mammalian cells. Both PRC1 and PRC2 compact chromatin, and also catalyze histone modifications. PRC1 mediates monoubiquitination of histone H2A, whereas PRC2 catalyzes methylation of histone H3 on lysine 27. These alterations of histones can lead to altered gene expression patterns by regulating chromatin structure. Numerous studies have highlighted the role of the PRC2 catalytic component enhancer of zeste homolog 2 (EZH2) in neoplastic development and progression, and EZH2 mutations have been identified in various malignancies. Through modulating the expression of critical genes, EZH2 is actively involved in fundamental cellular processes such as cell cycle progression, cell proliferation, differentiation and apoptosis. In addition to cancer cells, EZH2 also has a decisive role in the differentiation and function of T effector and T regulatory cells. In this review we summarize the recent progress regarding the role of EZH2 in human malignancies, highlight the molecular mechanisms by which EZH2 aberrations promote the pathogenesis of cancer, and discuss the anti-tumor effects of EZH2 targeting via activating direct anti-cancer mechanisms and anti-tumor immunity.

The role of EZH2 in overall survival of colorectal cancer: a meta-analysis

Enhancer of zeste homolog 2 (EZH2) is the catalitic subunit of polycomb repressive complex 2 and mediates gene silencing. EZH2 is overexpressed in many cancers and correlates with poor prognosis. The role of the gene EZH2 in colorectal cancer survival is uncertainly, the aim of this study is clear this relationship. Relevant literaure was searched from electronic databases. A meta-analysis was performed with elegible studies which quantitatively evaluated the relationship between EZH2 overexpression and survival of patients with colorectal cancer. Survival data were aggregated and quantitatively analyzed. We performed a meta-analysis of 8 studies (n = 1059 patients) that evaluated the correlation between EZH2 overexpression and survival in patients with colorectal cancer. Combined hazard ratios suggested that EZH2 overexpression was associated with better prognosis of overall survival (OS) HR(hazard ratio) = 0.61 95% CI (0.38-0.84) We performed bias analysis according Egger and Begg,s test and we did not find publication bias. EZH2 overexpression indicates a better prognosis for colorectal cancer.

Elevated expression of a pharmacologic Polycomb signature predicts poor prognosis in gastric and breast cancer

AIM

Polycomb Group complexes are epigenetic repressors that silence tumor suppressive genes. Studies demonstrated that pharmacologic inhibition of Polycomb Group complexes with 3-deazaneplanocin A (DZNeP) induces cancer cell death by re-expressing silenced genes. Here we evaluate the prognostic significance of DZNeP target genes in gastric and breast cancer. Patients & methods/materials: The prognostic impact of a DZNeP-regulated gene signature was investigated using the KM Plotter and cBio Portal resources containing microarray data from tumor tissue.

RESULTS

We report that elevated expression of DZNeP targets is associated with poor clinical outcome in gastric and breast cancer. In gastric cancer, elevated expression of DZNeP signature is inversely correlated with decreased overall survival. In breast cancer, DZNeP signature predicted poor prognosis in HER2+ tumors but not in HER2^- neoplasms.

CONCLUSION

These findings demonstrate that DZNeP target genes are not predictive of better but rather of poor clinical outcome in gastric and breast cancer.

Histone Chaperone ASF1A Predicts Poor Outcomes for Patients With Gastrointestinal Cancer and Drives Cancer Progression by Stimulating Transcription of β-Catenin Target Genes

Epigenetic mechanisms play a key role in gastrointestinal cancer (GIC) development and progression, and most studies have been focused on aberrant DNA methylation and histone modifying enzymes. However, the histone H3–H4 chaperone ASF1A is an important factor regulating chromatin assembling and gene transcription, while it is currently unclear whether ASF1A is involved in cancer pathogenesis. The present study is thus designed to address this issue. Here we showed that ASF1A expression was widespread in GIC-derived cell lines and up-regulated in primary GIC. Higher levels of ASF1A expression predicted significantly shorter patient overall survival in colorectal cancer (P = 0.0012). The further analyses of the GEO dataset validate higher ASF1A expression as a prognostic factor for CRC patients. Mechanistically, ASF1A interacted with β-catenin and promoted the transcription of β-catenin target genes including c-MYC, cyclin D1, ZEB1 and LGR5, thereby stimulating proliferation, stemness and migration/invasion of GIC cells. β-Catenin inhibition abolished these effects of ASF1A. Moreover, the ASF1A-β-catenin-ZEB1 axis down-regulated E-Cadherin expression, thereby contributing to enhanced migration/invasion of GIC cells. ASF1A over-expression and depletion facilitated and inhibited in vivo tumor growth and/or metastasis in mouse xenograft models, respectively. Taken together, ASF1A is aberrantly over-expressed in GIC tumors and plays key roles in GIC development and progression by stimulating the transcription of β-catenin target genes. ASF1A may thus be a novel target for GIC therapy and a potential prognostic marker.

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ASF1A is over-expressed in GIC and predicts poor patient outcomes.

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ASF1A interacts with β-catenin, facilitates the expression of its targets and promotes stemness and invasion of GIC cells.

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Targeting ASF1A could be a novel epigenetic strategy against GIC.

Gastrointestinal cancer (GIC) is the leading cause of cancer-related death worldwide and invasion or distant metastasis account for the majority of mortalities due to the limited treatment choices. We determined the effect of ASF1A, the histone H3–H4 chaperone, on GIC pathogenesis. We found that ASF1A expression was up-regulated in primary GIC and higher ASF1A levels predicted significantly shorter patient overall survival in colorectal cancer. ASF1A interacted with β-catenin and promoted the transcription of β-catenin target genes, thereby stimulating proliferation, stemness and migration/invasion of GIC cells. ASF1A may thus be a novel target for GIC therapy and a useful prognostic marker.

Dysregulation of histone methyltransferases in breast cancer - Opportunities for new targeted therapies?

Histone methyltransferases (HMTs) catalyze the methylation of lysine and arginine residues on histone tails and non-histone targets. These important post-translational modifications are exquisitely regulated and affect chromatin compaction and transcriptional programs leading to diverse biological outcomes. There is accumulating evidence that genetic alterations of several HMTs impinge on oncogenic or tumor-suppressor functions and influence both cancer initiation and progression. HMTs therefore represent an opportunity for therapeutic targeting in those patients with tumors in which HMTs are dysregulated, to reverse the histone marks and transcriptional programs associated with aggressive tumor behavior. In this review, we describe the known histone methyltransferases and their emerging roles in breast cancer tumorigenesis.

Methyltransferase expression and tumor suppressor gene methylation in sporadic and familial colorectal cancer

Molecular mechanisms underlying coordinated hypermethylation of multiple CpG islands in cancer remain unclear and studies of methyltransferase enzymes have arrived at conflicting results. We focused on DNMT1 and DNMT3B, DNA methyltransferases responsible for (de novo) methylation, and EZH2, histone (H3K27) methyltransferase, and examined their roles in tumor suppressor gene (TSG) methylation patterns we have previously established in sporadic and familial cancers. Our investigation comprised 165 tumors, stratified by tissue of origin (117 colorectal and 48 endometrial carcinomas) and sporadic vs. familial disease (57 sporadic vs. 60 familial, mainly Lynch syndrome, colorectal carcinomas). By immunohistochemical evaluation, EZH2 protein expression was associated with a TSG methylator phenotype. DNMT1, DNMT3B, and EZH2 were expressed at significantly higher levels in tumor vs. normal tissues. DNMT1 and EZH2 expression were positively correlated and higher in microsatellite-unstable vs. microsatellite-stable tumors, whether sporadic or hereditary. Ki-67 expression mirrored the same pattern. Promoter methylation of the methyltransferase genes themselves was addressed as a possible cause behind their altered expression. While DNMT1 or EZH2 did not show differential methylation between normal and tumor tissues, DNMT3B analysis corroborated the regulatory role of a distal promoter region. Our study shows that methyltransferase expression in cancer depends on the tissue of origin, microsatellite-instability status, cellular proliferation, and--in the case of DNMT3B--promoter methylation of the respective gene. Translation of methyltransferase expression into DNA methylation appears complex as suggested by the fact that except for EZH2, no clear association between methyltransferase protein expression and TSG methylation was observed.

Molecular and pathological characterization of the EZH2 rs3757441 single nucleotide polymorphism in colorectal cancer

Background

The enhancer of zeste-homolog 2 (EZH2) is involved in cancer development through gene silencing by trimethylation of lysine 27 of histone 3 (H3K27me3). The C/C genotype for the EZH2 rs3757441 single-nucleotide polymorphism (SNP) is linked with poor prognosis in metastatic colorectal cancer (CRC), but molecular and pathological characterization of this SNP is lacking.

Methods

119 primary CRCs were analyzed. SNP was evaluated by real-time PCR from colonic healthy tissue, while EZH2 and H3K27me3 expression were studied by immunohistochemistry. We primarily looked for correlation between EZH2 rs3757441 genotypes and EZH2/H3K27me3 expression. Potential associations between EZH2/H3K27me3 expression and clinico-pathological features or KRAS exon 2 and BRAF exon 15 mutations were secondary endpoints. Statistical analysis was performed by chi-square test, T-test or ANOVA.

Results

The C/C genotype was significantly associated with higher EZH2 (100 vs. 44 %; P = 0.019) and H3K27me3 (100 vs. 38 %; P = 0.009) staining intensity compared with C/T and T/T. EZH2 3+ staining significantly correlated with stronger H3K27me3 expression (P = 0.039). KRAS and BRAF mutations were not associated with EZH2 or H3K27me3 expression.

Conclusion

EZH2 rs3757441 C/C genotype is associated with stronger EZH2 and H3K27me3 immunoreactivity in primary CRC: this SNP may serve as a promising biomarker for EZH2-targeting agents and may add independent information to KRAS and BRAF testing.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1889-2) contains supplementary material, which is available to authorized users.

Mutation spectra of histone methyltransferases with canonical SET domains and EZH2-targeted therapy

Germline mutations in canonical SET-methyltransferases have been identified in autism and intellectual disability syndromes and gain-of-function somatic alterations in EZH2, MLL3, NSD1, WHSC1 (NSD2) and WHSC1L1 (NSD3) in cancer. EZH2 interacts with AR, ERα, β-catenin, FOXP3, NF-κB, PRC2, REST and SNAI2, resulting in context-dependent transcriptional activation and repression. Pharmacological EZH2 inhibitors are currently in clinical trials for the treatment of B-cell lymphomas and solid tumors. EZH2 inhibitors might also be applicable in the treatment of SWI/SNF-mutant cancers, reflecting the reciprocal expression of and functional overlap between EZH2 and SMARCA4. Because of the risks for autoimmune diseases, cognitive impairment, cardiomyopathy and myelodysplastic syndrome, EZH2 inhibitors should be utilized for cancer treatment in patients receiving long-term surveillance but not for cancer chemoprevention.

The possible role of EZH2 and DNMT1 polymorphisms in sporadic triple-negative breast carcinoma in southern Chinese females

Triple-negative breast cancer (TNBC) has a more invasive and metastatic potential than the other types of breast cancer and hence is associated with poor prognosis. Zeste homolog 2 (EZH2) and DNA methyltransferase 1 (DNMT1) could lead to tumorigenesis by separately methylating histone H3K27 and CpG islands in tumor suppressor genes. In order to investigate the association between oncogenesis and the distribution of single nucleotide polymorphisms (SNPs) of EZH2, DNMT1, a case-control study on SNPs in TNBC cases from south China was conducted. A total of 13 SNPs were genotyped from 234 cases of TNBC tissues, and 300 normal blood samples from age-matched control group were analyzed using Snapshot technology. The expressions of EZH2 and DNMT1 were examined in the 234 cases of TNBC tissues by immunohistochemistry (IHC). The T allele of rs2288349 and the C allele of rs16999593 increase the risk of TNBC, with relative risk coefficients of 1.76 and 1.69, respectively (p < 0.001). The TC genotypes of rs2288349 and rs16999593 were higher in TNBC compared with the control group; the cancer risk increased to 5.27 and 4.13, respectively (p < 0.001). There were no significant differences between the frequencies of the other 10 SNPs and the risk of TNBC (p > 0.05). Five common haplotypes (>8 % frequency) were identified with a cumulative frequency of 96 % in the controls, while the haplotypes of AAGTAG, GGGTGA, and GACCAG were significantly increased in the control group compared to that in patients (p < 0.05). The G allele of rs10274701 significantly increased the EZH2 expression level in TNBC (p = 0.01). This is the first study to demonstrate a significant association between TNBC risk and the polymorphisms of EZH2 and DNMT1, and our researches indicate that the SNPs of EZH2 and DNMT1 are risk predictors for TNBC.

Enhancer of zeste homolog 2 as an independent prognostic marker for cancer: a meta-analysis

Background

Novel biomarkers are of particular interest for predicting cancer prognosis. This study aimed to explore the associations between enhancer of zeste homolog 2 (EZH2) and patient survival in various cancers.

Methods

Relevant literature was retrieved from PubMed and Web of Science databases. Pooled hazard ratios (HRs), odds ratios (ORs), and 95% confidence intervals (CIs) were calculated.

Results

Forty-nine studies (8,050 patients) were included. High EZH2 expression was significantly associated with shorter overall (hazard ratio [HR] 1.74, 95% CI: 1.46–2.07), disease-free (HR 1.59, 95% CI: 1.27–1.99), metastasis-free (HR 2.19, 95% CI: 1.38–3.47), progression-free (HR 2.53, 95% CI: 1.52–4.21), cancer-specific (HR 3.13, 95% CI: 1.70–5.74), and disease-specific (HR 2.29, 95% CI: 1.56–3.35) survival, but not recurrence-free survival (HR 1.38, 95% CI: 0.93–2.06). Moreover, EZH2 expression significantly correlated with distant metastasis (OR 3.25, 95% CI: 1.07–9.87) in esophageal carcinoma; differentiation (OR 3.00, 95% CI: 1.37–6.55) in non-small cell lung cancer; TNM stage (OR 3.18, 95% CI: 2.49–4.08) in renal cell carcinoma; and histological grade (OR 4.50, 95% CI: 3.33–6.09), estrogen receptor status (OR 0.15, 95% CI: 0.11–0.20) and progesterone receptor status (OR 0.30, 95% CI: 0.23–0.39) in breast cancer.

Conclusions

Our results suggested that EZH2 might be an independent prognostic factor for multiple survival measures in different cancers.

Examining the impact of gene variants on histone lysine methylation

In recent years, there has been a boom in the amount of genome-wide sequencing data that has uncovered important and unappreciated links between certain genes, families of genes and enzymatic processes and diseases such as cancer. Such studies have highlighted the impact that chromatin modifying enzymes could have in cancer and other genetic diseases. In this review, we summarize characterized mutations and single nucleotide polymorphisms (SNPs) in histone lysine methyltransferases (KMTs), histone lysine demethylases (KDMs) and histones. We primarily focus on variants with strong disease correlations and discuss how they could impact histone lysine methylation dynamics and gene regulation.

Prognostic value of polycomb proteins EZH2, BMI1 and SUZ12 and histone modification H3K27me3 in colorectal cancer

Numerous changes in epigenetic mechanisms have been described in various types of tumors. In search for new biomarkers, we investigated the expression of Polycomb-group (PcG) proteins EZH2, BMI1 and SUZ12 and associated histone modification H3K27me3 in colorectal cancer. Nuclear expression of PcG proteins and histone modification H3K27me3 were immunohistochemically (IHC) stained on a tissue microarray (TMA), including 247 tumor tissues and 47 normal tissues, and scored using the semi-automated Ariol system. Tumor tissues showed higher expression of EZH2 (p = 0.05) and H3K27me3 (p<0.001) as compared to their normal counterparts. Combined marker trend analyses indicated that an increase in the number of markers showing high expression was associated with better prognosis. High expression of all four markers in the combined marker analyses was correlated with the best patient survival and the longest recurrence-free survival, with overall survival (p = 0.01, HR 0.42(0.21-0.84)), disease-free survival (p = 0.007, HR 0.23(0.08-0.67) and local recurrence-free survival (p = 0.02, HR 0.30(0.11-0.84)). In conclusion, we found that expression of PcG proteins and H3K27me3 showed prognostic value in our study cohort. Better stratification of patients was obtained by combining the expression data of the investigated biomarkers as compared to the individual markers, underlining the importance of investigating multiple markers simultaneously.

Role of EZH2 polymorphisms in esophageal squamous cell carcinoma risk in Han Chinese population

Gene single nucleotide polymorphisms play a critical role in the development of esophageal squamous cell carcinoma (ESCC). The aim of this study is to investigate the associations between EZH2 gene polymorphisms and ESCC risk. We undertook a case-control study to analyze three EZH2 polymorphisms (148505302C>T, 2110+6A>C and 626-394T>C) in an Han Chinese population, by extraction of genomic DNA from the peripheral blood of 476 patients with ESCC and 492 control participants, and performed EZH2 genotyping using DNA sequencing. The obtained results indicated that overall, no statistically significant association was observed in 148505302C>T and 2110+6A>C. However, 626-394T>C genotype was at increased risk of ESCCs (p=0.006; odds ratio (OR)=1.131, CI 95%: 1.034-1.236). Moreover, 626-394C/C genotype ESCCs were more significantly common in patients with tumor size of >5 cm than T allele ESCC and in cases of poor differentiation and lower advanced pathological stage. In conclusion, polymorphism in 626-394T>C was observed to be associated with susceptibility of ESCC. Nevertheless, further investigation with a larger sample size is needed to support our results.

Epigenetic mechanisms of tumorigenicity manifesting in stem cells

One of the biggest roadblocks to using stem cells as the basis for regenerative medicine therapies is the tumorigenicity of stem cells. Unfortunately, the unique abilities of stem cells to self-renew and differentiate into a variety of cell types are also mechanistically linked to their tumorigenic behaviors. Understanding the mechanisms underlying the close relationship between stem cells and cancer cells has therefore become a primary goal in the field. In addition, knowledge gained from investigating the striking parallels between mechanisms orchestrating normal embryogenesis and those that invoke tumorigenesis may well serve as the foundation for developing novel cancer treatments. Emerging discoveries have demonstrated that epigenetic regulatory machinery plays important roles in normal stem cell functions, cancer development, and cancer stem cell identity. These studies provide valuable insights into both the shared and distinct mechanisms by which pluripotency and oncogenicity are established and regulated. In this review, the cancer-related epigenetic mechanisms found in pluripotent stem cells and cancer stem cells will be discussed, focusing on both the similarities and the differences.

Impact of EZH2 polymorphisms on urothelial cell carcinoma susceptibility and clinicopathologic features

Background

The gene EZH2, the polycomb group protein enhancer of zeste 2, encodes a transcriptional repressor that also serves as a histone methyltransferase that is associated with progression to more advanced disease in a variety of malignancies. EZH2 expression level in urothelial cell carcinoma (UCC) is highly correlated with tumor aggressiveness, but it has not been determined if specific EZH2 genetic variants are associated with UCC risk. This study investigated the potential associations of EZH2 single-nucleotide polymorphisms with UCC susceptibility and its clinicopathologic characteristics.

Methodology/Principal Findings

A total of 233 UCC patients and 552 cancer-free controls, all of whom were from Taiwan, were analyzed for four EZH2 single-nucleotide polymorphisms (rs6950683, rs2302427, rs3757441, and rs41277434) using real-time PCR genotyping. After adjusting for other co-variants, we found that individuals carrying at least one C allele at EZH2 rs6950683 had a lower risk of developing UCC than did major allele carriers. The CCCA or TGTA haplotype among the four EZH2 sites was also associated with a reduced risk of UCC. Furthermore, UCC patients who carried at least one G allele at rs2302427 had a lower invasive tumor stage than did patients carrying the major allele.

Conclusions

The rs6950683 SNPs of EZH2 might contribute to the prediction of UCC susceptibility. This is the first study to provide insight into risk factors associated with EZH2 variants in carcinogenesis of UCC in Taiwan.

A polymorphism in the promoter is associated with EZH2 expression but not with outcome in advanced pancreatic cancer patients

Aim: EZH2 expression is a prognostic marker in radically resected pancreatic ductal adenocarcinoma (PDAC) patients. Here we investigated its role in locally advanced/metastatic patients, as well as candidate polymorphisms. Materials & methods: EZH2 expression and polymorphisms were evaluated by quantitative reverse transcription PCR in 32 laser microdissected tumors, while polymorphisms were also studied in blood samples from two additional cohorts treated with gemcitabine monotherapy (n = 93) or polychemotherapeutic regimens (n = 247). Results: EZH2 expression correlated with survival and with the rs6958683 polymorphism in the first cohort of patients, but this polymorphism was not associated with survival in our larger cohorts. Conclusion: EZH2 is a prognostic factor for locally advanced/metastatic PDACs, while candidate polymorphisms cannot predict clinical outcome. Other factors involved in EZH2 regulation, such as miR-101, should be investigated in accessible samples in order to improve the clinical management of advanced PDAC.

Original submitted 31 July 2013; Revision submitted 4 November 2013

Association between EZH2 polymorphisms and colorectal cancer risk in Han Chinese population

The aim of this study is to investigate the associations between EZH2 gene polymorphisms and colorectal cancer (CRC) risk. We undertook a case-control study to analyze three EZH2 polymorphisms (148505302C>T, 2110+6A>C and 626-394T>C) in an Han Chinese population, by extraction of genomic DNA from the peripheral blood of 512 patients with CRC and 546 control participants, and performed EZH2 genotyping using DNA sequencing. The obtained results indicated that overall, no statistically significant association was observed in 2,110+6A>C. Nevertheless, 148505302C>T genotype demonstrated a protective effect in CRCs (P=0.014; odds ratio (OR) 0.777, CI 95%:0.647-0.933). Furthermore, 148505302 T allele CRC was more significantly common in patients with tumor size of <4 cm than C allele CRC and in cases of good differentiation and lower advanced pathological stage. However, 626-394T>C genotype was at increased risk of CRCs (P<0.001; odds ratio (OR) 1.457, CI 95%:1.160-1.829). Moreover, 626-394C/C genotype CRCs were more significantly common in patients with tumor size of >4 cm than T allele CRC and in cases of poor differentiation and lower advanced pathological stage. In conclusion, polymorphism in 626-394T>C was observed to be associated with susceptibility of CRC. However, 148505302C>T polymorphism indicated to play a protective role in susceptibility to CRC. Nevertheless, further investigation with a larger sample size is needed to support our results.

How to select the optimal treatment for first line metastatic colorectal cancer

Choice of first line treatment for patients with metastatic colorectal cancer (mCRC) is based on tumour and patient related factors and molecular information for determination of individual treatment aim and thus treatment intensity. Recent advances (e.g., extended RAS testing) enable tailored patient assignment to the most beneficial treatment approach. Besides fluoropyrimidines, irinotecan and oxaliplatin, a broad variety of molecular targeting agents are currently available, e.g., anti-angiogenic agents (bevacizumab) and epidermal growth factor receptor (EGFR) antibodies (cetuximab, panitumumab) for first line treatment of mCRC. Although some combinations should be avoided (e.g., oral or bolus fluoropyrimidines, oxaliplatin and EGFR antibodies), treatment options range from single agent to highly effective four-drug regimen. Preliminary data comparing EGFR antibodies and bevacizumab, both with chemotherapy, seem to favour EGFR antibodies in RAS wildtype disease. However, choosing the most appropriate treatment approach for mCRC patients remains a complex issue, with numerous open questions.

A genetic variant in microRNA target site of TGF-β signaling pathway increases the risk of colorectal cancer in a Chinese population

Evidence shows that single-nucleotide polymorphisms in microRNA (miRNA) target sites can create, destroy, or modify the miRNA/mRNA binding, therefore modulating gene expression and affecting cancer susceptibility. The transforming growth factor-β (TGF-β) signaling pathway plays a pivotal role in tumor initiation and progression. Intriguingly, recent advances of genome-wide association studies have identified multiple risk loci in this pathway to be associated with risk of colorectal cancer (CRC). To test the hypothesis that genetic variants in miRNA target sites in genes of the TGF-β signaling pathway may also be associated with CRC risk, we first systematically scanned the single-nucleotide polymorphisms (SNPs) in genes of TGF-β signaling pathway which potentially affect the miRNA/mRNA bindings. Through a series of filters, we narrowed down these candidates to four SNPs. Then, we conducted a case-control study with 600 CRC patients and 638 controls in Han Chinese population. We observed that compared with A carriers (AA + AG), the GG genotype of rs12997:ACVR1 is associated with a significantly higher risk of CRC (OR = 1.52, 95% confidence interval (95% CI) = 1.04-2.21, P = 0.031), particularly in nonsmokers with a higher OR of 1.63 (95% CI = 1.04-2.55, P = 0.032). Our study suggested that SNPs in miRNA target sites could contribute to the likelihood of CRC susceptibility and emphasized the important role of polymorphisms at miRNA-regulatory elements in carcinogenesis.

Effects of EZH2 polymorphisms on susceptibility to and pathological development of hepatocellular carcinoma

Background

The enhancer of zeste 2 (EZH2) gene encodes the histone methyltransferase that is the catalytic component of the polycomb repressive complex-2, which initiates epigenetic silencing of genes. The expression level of EZH2 in hepatocellular carcinoma (HCC) is highly correlated with tumor progression; however, it has not been determined if specific EZH2 genetic variants are associated with the risk of HCC. This study investigated the potential associations of EZH2 single-nucleotide polymorphisms with HCC susceptibility and its clinicopathologic characteristics.

Methodology/Principal Findings

A total of 220 HCC patients and 552 cancer-free controls were analyzed for four EZH2 single-nucleotide polymorphisms (rs6950683, rs2302427, rs3757441, and rs41277434) using real-time PCR genotyping. After adjusting for other co-variants, the individuals carrying at least one C allele at EZH2 rs6950683 and rs3757441 had a 0.611-fold and a 0.660-fold lower risk of developing HCC than did wild-type (TT) carriers, respectively. The CCCA or CCTA haplotype among the four EZH2 sites (rs6950683, rs2302427, rs3757441, and rs41277434), respectively, was also associated with a reduced risk of HCC. Furthermore, HCC patients who carried at least one C allele at rs6950683 or rs3757441 had a higher lymph–node-metastasis risk but a lower liver-cirrhosis risk than did patients carrying the wild-type allele.

Conclusions

The rs6950683 and rs3757441 polymorphic genotypes of EZH2 might contribute to the prediction of susceptibility to and pathological development of HCC. This is the first study to provide insight into risk factors associated with EZH2 variants in carcinogenesis of HCC in Taiwan.

Epigenetic biomarkers in colorectal cancer diagnostics

Colorectal cancer (CRC) is a significant health burden worldwide. Despite advancements in treatment options, improvements in CRC patient survival have been limited owing to lack of early detection and limited capacity for optimal therapeutic decision-making. Biomarkers to improve CRC diagnosis, prognosis and prediction of treatment response therefore represent opportunities to improve patient outcome. In addition to genetic alterations and genomic instability, it is now clear that epigenetic alterations play dramatic roles in driving tumor onset and progression in CRC. A recent surge in investigation of epigenetic biomarkers including DNA methylation, miRNA expression and histone modifications has demonstrated that these alterations may be enticing translational biomarker candidates in CRC. In particular, methylation kits have already been incorporated into clinical practice for a handful of cancers, including CRC. This review will aim to summarize the established and emerging roles of epigenetic modifications in CRC detection, prognostication and prediction of treatment response.

Epigenetic mechanisms in commonly occurring cancers

Cancer is a collection of very complex diseases that share many traits while differing in many ways as well. This makes a universal cure difficult to attain, and it highlights the importance of understanding each type of cancer at a molecular level. Although many strides have been made in identifying the genetic causes for some cancers, we now understand that simple changes in the primary DNA sequence cannot explain the many steps that are necessary to turn a normal cell into a rouge cancer cell. In recent years, some research has shifted to focusing on detailing epigenetic contributions to the development and progression of cancer. These changes occur apart from primary genomic sequences and include DNA methylation, histone modifications, and miRNA expression. Since these epigenetic modifications are reversible, drugs targeting epigenetic changes are becoming more common in clinical settings. Daily discoveries elucidating these complex epigenetic processes are leading to advances in the field of cancer research. These advances, however, come at a rapid and often overwhelming pace. This review specifically summarizes the main epigenetic mechanisms currently documented in solid tumors common in the United States and Europe.

MicroRNA-98 and microRNA-214 post-transcriptionally regulate enhancer of zeste homolog 2 and inhibit migration and invasion in human esophageal squamous cell carcinoma

Background

The enhancer of zeste homolog 2 (EZH2) was found to be overexpressed and associated with tumor metastasis in esophageal squamous cell carcinoma (ESCC). On the other hand, it was reported that miR-26a, miR-98, miR-101, miR-124, miR-138 and miR-214 could inhibit the expression of EZH2 in some tumors. However, the role of miRNAs in the regulation of EZH2 expression in human ESCC has not been documented. The aim of this study was to determine the role of these miRNAs in the regulation of tumor metastasis via EZH2 overexpression in human ESCC.

Methods and results

The expression of these miRNAs and EZH2 mRNA were examined by qPCR and the expression of EZH2 protein was detected by western blot. The role of these miRNAs in migration and invasion was studied in ESCC cell line (Eca109) transfected with miRNA mimics or cotransfected with miRNA mimics and pcDNA-EZH2 plasmid (without the 3’-UTR of EZH2). Through clinical investigation, we found that miR-98 and miR-214 expression was significantly lower in ESCC tissues than in matched normal tissues, and the expression level of miR-98 and miR-214 was inversely correlated to EZH2 protein expression and the clinical features such as pathological grade, tumor stage and lymph node metastasis in ESCC. In Eca109 cells, overexpression of miR-98 and miR-214 significantly inhibited the migration and invasion of ESCC cells, which was reversed by transfection of EZH2.

Conclusions

These findings suggest that decreased expression of miR-98 and miR-214 might promote metastasis of human ESCC by inducing accumulation of EZH2 protein.

Overexpression of enhancer of zeste homolog 2 (EZH2) and focal adhesion kinase (FAK) in high grade endometrial carcinoma

OBJECTIVE

The deregulation of E-cadherin is associated with Src/FAK signaling axis and histone deacetylase (HDAC)/EZH2 activity. However, the association between EZH2 and FAK and its clinical significance in endometrial carcinoma has not been reported.

METHODS

202 archived cases of endometrial carcinoma (1996-2000) were reviewed and divided into two subtypes. TMAs were developed as per established procedures. EZH2, FAK, and pFAK immunohistochemical stains were performed and the expression was scored as negative (0), low (1) and high (2). Proper statistical analysis was used to assess the correlation between the expression profiles and the clinicopathological parameters and clinical outcome.

RESULTS

A total of 141 (69.8%) type-1 tumors and 61 (30.2%) type-2 tumors were identified. EZH2 overexpression was identified in 7.6% of type-1 tumors vs. 63% of type-2 tumors (p<0.001). FAK and pFAK overexpression was only seen in 24.8% and 1.7% of Type-1 tumors as compared to 72% and 58.8% of type-2 tumors, respectively (p<0.001). A positive correlation between the expression of EZH2, FAK, pFAK and PTEN (p<0.0001) was found. The overexpression of EZH2, FAK, and pFAK were significantly associated with high histologic grade, angiolymphatic invasion, lymph node metastasis, myometrial invasion and cervical involvement (p<0.01). Kaplan-Meier analysis demonstrates that the overexpression of EZH2 (p=0.0024), FAK and pFAK (p=0.0001) was significantly associated with decreased overall survival.

CONCLUSION

The overexpression of EZH2, FAK and pFAK correlates with well established pathologic risk factors and may predict a more aggressive biologic behavior in endometrial carcinoma, transforming these proteins into potential therapeutic targets for treatment of endometrial cancer.

Suppression of colorectal cancer metastasis by nigericin through inhibition of epithelial-mesenchymal transition

AIM: To evaluate the effect of nigericin on colorectal cancer and to explore its possible mechanism.

METHODS: The human colorectal cancer (CRC) cell lines HT29 and SW480 were treated with nigericin or oxaliplatin under the conditions specified. Cell viability assay and invasion and metastasis assay were performed to evaluate the effect of nigericin on CRC cells. Sphere-forming assay and soft agar colony-forming assay were implemented to assess the action of nigericin on the cancer stem cell properties of CRC cells undergone epithelial-mesenchymal transition (EMT).

RESULTS: Compared with oxaliplatin, nigericin showed more toxicity for the HT29 cell line (IC50, 12.92 ± 0.25 μmol vs 37.68 ± 0.34 μmol). A similar result was also obtained with the SW116 cell line (IC50, 15.86 ± 0.18 μmol vs 41.02 ± 0.23 μmol). A Boyden chamber assay indicated that a significant decrease in the number of HT29 cells migrating through polyvinylidene fluoride membrane was observed in the nigericin-treated group, relative to the vehicle-treated group [11 ± 2 cells per high-power field (HPF) vs 19.33 ± 1.52 cells per HPF, P < 0.05]. Compared to the control group, the numbers of HT29 cells invading through the Matrigel-coated membrane also decreased in the nigericin-treated group (6.66 ± 1.52 cells per HPF vs 14.66 ± 1.52 cells per HPF, P < 0.05). Nigericin also reduced the proportion of CD133⁺ cells from 83.57% to 63.93%, relative to the control group (P < 0.05). Nigericin decreased the number of spheres relative to the control group (0.14 ± 0.01 vs 0.35 ± 0.01, P < 0.05), while oxaliplatin increased the number of spheres relative to the control group (0.75 ± 0.02 vs 0.35 ± 0.01; P < 0.05). Nigericin also showed a decreased ability to form colonies under anchorage-independent conditions in a standard soft agar assay after 14 d in culture, relative to the control group (1.66 ± 0.57 vs 7 ± 1.15, P < 0.05), whereas the colony numbers were higher in the oxaliplatin group relative to the vehicle-treated controls (14.33 ± 0.57 vs 7 ± 1.15, P < 0.05). We further detected the expression of E-cadherin and vimentin in cells treated with nigericin and oxaliplatin. The results showed that HT29 cells treated with nigericin induced an increase in E-cadherin expression and a decrease in the vimentin expression relative to vehicle controls. In contrast, oxaliplatin downregulated the expression of E-cadherin and upregulated the expression of vimentin in HT29 cells relative to vehicle controls.

CONCLUSION: This study demonstrated that nigericin could partly reverse the EMT process during cell invasion and metastasis.

EZH2 genetic variants affect risk of gastric cancer in the Chinese Han population

Enhancer of zeste 2 (EZH2) gene encodes a histone methyltransferase that constitutes the catalytic component of the polycomb repressive complex-2 (PRC2) to initiate epigenetic silencing of genes. It is reported that the expression level of EZH2 in gastric cancer tissue was highly correlated with tumor progression, however, whether EZH2 genetic variants were associated with the risk of gastric cancer remains yet unknown. In this study, we conducted a genotyping analysis for EZH2 in 311 cases of gastric cancer and 425 controls from the Chinese Han population. We found five single nucleotide polymorphisms (SNP; rs12670401, rs6464926, rs2072407, rs734005, and rs734004) of EZH2 gene were significantly associated with the risk of gastric cancer. Of which, the rs12670401 with the minor allele C and rs6464926 with the minor allele T revealed strong associations with increased gastric cancer risk [P = 0.009, adjusted odds ratio (aOR) = 1.327, 95% CI = 1.075-1.683 and P = 0.012, aOR = 1.310, 95% CI = 1.059-1.619]. The other three SNPs, rs2072407, rs734005, and rs734004 contributed to significantly reduced risk of gastric cancer (P = 0.033, aOR = 0.787, 95% CI = 0.633-0.981, P = 0.045, aOR = 0.799, 95% CI = 0.642-0.995 and P = 0.048, aOR = 0.803, 95% CI = 0.645-0.999), respectively. We further found that rs12670401 and rs6464926 were in a strong LD while rs2072407, rs734005, and rs734004 were in another. Haplotype analysis of the five SNPs showed that haplotype CCTCT reduced the risk of gastric cancer (P = 0.031 and aOR = 0.784), while haplotype GTCTC significantly elevated the risk of gastric cancer (P = 0.011 and aOR = 1.310). We concluded that EZH2 variants were significantly associated with gastric cancer risk. Our results for the first time provided new insight into susceptibility factors of EZH2 gene variants in carcinogenesis of gastric cancer of the Chinese Han population.