Aberrant gene methylation in non-neoplastic mucosa as a predictive marker of ulcerative colitis-associated CRC

Effects of DNA methylation and its application in inflammatory bowel disease (Review)

Inflammatory bowel disease (IBD) is marked by persistent inflammation, and its development and progression are linked to environmental, genetic, immune system and gut microbial factors. DNA methylation (DNAm), as one of the protein modifications, is a crucial epigenetic process used by cells to control gene transcription. DNAm is one of the most common areas that has drawn increasing attention recently, with studies revealing that the interleukin (IL)‑23/IL‑12, wingless‑related integration site, IL‑6‑associated signal transducer and activator of transcription 3, suppressor of cytokine signaling 3 and apoptosis signaling pathways are involved in DNAm and in the pathogenesis of IBD. It has emerged that DNAm‑associated genes are involved in perpetuating the persistent inflammation that characterizes a number of diseases, including IBD, providing a novel therapeutic strategy for exploring their treatment. The present review discusses DNAm‑associated genes in the pathogenesis of IBD and summarizes their application as possible diagnostic, prognostic and therapeutic biomarkers in IBD. This may provide a reference for the particular form of IBD and its related methylation genes, aiding in clinical decision‑making and encouraging therapeutic alternatives.

Molecular Pathogenesis of Colitis-associated Colorectal Cancer: Immunity, Genetics, and Intestinal Microecology

Patients with inflammatory bowel disease (IBD) have a high risk for colorectal cancer (CRC). This cancer type, which is strongly associated with chronic inflammation, is called colitis-associated CRC (CAC). Understanding the molecular pathogenesis of CAC is crucial to identify biomarkers necessary for early diagnosis and more effective treatment directions. The accumulation of immune cells and inflammatory factors, which constitute a complex chronic inflammatory environment in the intestinal mucosa, may cause oxidative stress or DNA damage to the epithelial cells, leading to CAC development and progression. An important feature of CAC is genetic instability, which includes chromosome instability, microsatellite instability, hypermethylation, and changes in noncoding RNAs. Furthermore, the intestinal microbiota and metabolites have a great impact on IBD and CAC. By clarifying immune, genetic, intestinal microecology, and other related pathogenesis, CAC may be more predictable and treatable.

Inflammatory Bowel Disease and Risk of Colorectal Cancer: An Overview From Pathophysiology to Pharmacological Prevention

Increased risk of colorectal cancer (CRC) in inflammatory bowel disease (IBD) patients has been attributed to long-standing chronic inflammation, with the contribution of genetic alterations and environmental factors such as the microbiota. Moreover, accumulating data indicate that IBD-associated CRC (IBD-CRC) may initiate and develop through a pathway of tumorigenesis distinct from that of sporadic CRC. This mini-review summarizes the current knowledge of IBD-CRC, focusing on the main mechanisms underlying its pathogenesis, and on the important role of immunomodulators and biologics used to treat IBD patients in interfering with the inflammatory process involved in carcinogenesis.

Immunoprofiles and DNA Methylation of Inflammatory Marker Genes in Ulcerative Colitis-Associated Colorectal Tumorigenesis

Immunological and epigenetic changes are interconnected and contribute to tumorigenesis. We determined the immunoprofiles and promoter methylation of inflammation-related genes for colitis-associated colorectal carcinomas (CA-CRC). The results were compared with Lynch syndrome (LS)-associated colorectal tumors, which are characterized by an active immune environment through inherited mismatch repair defects. CA-CRCs (n = 31) were immunohistochemically evaluated for immune cell scores (ICSs) and PDCD1 and CD274 expression. Seven inflammation-associated genes (CD274, NTSR1, PPARG, PTGS2, PYCARD, SOCS1, and SOCS2), the repair gene MGMT, and eight standard marker genes for the CpG Island Methylator Phenotype (CIMP) were investigated for promoter methylation in CA-CRCs, LS tumors (n = 29), and paired normal mucosae by multiplex ligation-dependent probe amplification. All but one CA-CRCs were microsatellite-stable and all LS tumors were microsatellite-unstable. Most CA-CRCs had a high ICS (55%) and a positive CD274 expression in immune cells (52%). NTSR1 revealed frequent tumor-specific hypermethylation in CA-CRC and LS. When compared to LS mucosae, normal mucosae from patients with CA-CRC showed significantly higher methylation of NTSR1 and most CIMP markers. In conclusion, CA-CRCs share a frequent ICS^high/CD274^pos expression pattern with LS tumors. Elevated methylation in normal mucosa may indicate field cancerization as a feature of CA-CRC-associated tumorigenesis.

Predicting Colorectal Cancer Occurrence in IBD

Patients with colonic inflammatory bowel disease (IBD) are at an increased risk of developing colorectal cancer (CRC), and are therefore enrolled into a surveillance programme aimed at detecting dysplasia or early cancer. Current surveillance programmes are guided by clinical, endoscopic or histological predictors of colitis-associated CRC (CA-CRC). We have seen great progress in our understanding of these predictors of disease progression, and advances in endoscopic technique and management, along with improved medical care, has been mirrored by the falling incidence of CA-CRC over the last 50 years. However, more could be done to improve our molecular understanding of CA-CRC progression and enable better risk stratification for patients with IBD. This review summarises the known risk factors associated with CA-CRC and explores the molecular landscape that has the potential to complement and optimise the existing IBD surveillance programme.

Role of miR-506 in ulcerative colitis associated with primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is commonly accompanied by ulcerative colitis (UC). MicroRNA-506 modulates expression of genes which are essential for sphingosine-mediated signaling pathway and intestinal mucosa protection. We investigated whether miR-506 and its target genes are involved in phenotypic presentations of colonic inflammation and/or neoplasia. We analyzed serum and colon tissue samples collected from patients with PSC, PSC with concurrent UC (PSC + UC), UC alone, and healthy controls (n = 10 each). MiR-506 was substantially upregulated in ascending colons of PSC and PSC + UC patients, in contrast to sigmoid colons of PSC and UC patients. Upregulation of miR-506 was associated with inhibition of SPHK1, AE2, InsP3R3, and p53. Colonic suppression of miR-506 presented in UC was accompanied by substantially increased DNMT1, SPHK1, and S1P lyase expressions. A functional in vitro analysis in Caco-2 cells showed that the induction of miR-506 activity by miR-506 mimic or GDCDA bile acid suppressed, whereas inhibition of miR-506 by miR-506 inhibitor or lipopolysaccharide (LPS) upregulated the expression of the examined target genes. A different phenotypic presentation of colitis may be related to miR-506 expression. In ascending colons with PSC + UC, upregulation of miR-506 may result in failure of bicarbonate secretion and inhibition of p53, which predisposes to pro-tumorigenic transformation. In contrast, downregulation of miR-506 enhances S1P production, leading to pro-inflammatory signaling.

Somatic mutation profiles as molecular classifiers of ulcerative colitis-associated colorectal cancer

Ulcerative colitis increases colorectal cancer risk by mechanisms that remain incompletely understood. We approached this question by determining the genetic and epigenetic profiles of colitis-associated colorectal carcinomas (CA-CRC). The findings were compared to Lynch syndrome (LS), a different form of cancer predisposition that shares the importance of immunological factors in tumorigenesis. CA-CRCs (n = 27) were investigated for microsatellite instability, CpG island methylator phenotype and somatic mutations of 999 cancer-relevant genes ("Pan-cancer" panel). A subpanel of "Pan-cancer" design (578 genes) was used for LS colorectal tumors (n = 28). Mutational loads and signatures stratified CA-CRCs into three subgroups: hypermutated microsatellite-unstable (Group 1, n = 1), hypermutated microsatellite-stable (Group 2, n = 9) and nonhypermutated microsatellite-stable (Group 3, n = 17). The Group 1 tumor was the only one with MLH1 promoter hypermethylation and exhibited the mismatch repair deficiency-associated Signatures 21 and 15. Signatures 30 and 32 characterized Group 2, whereas no prominent single signature existed in Group 3. TP53, the most common mutational target in CA-CRC (16/27, 59%), was similarly affected in Groups 2 and 3, but DNA repair genes and Wnt signaling genes were mutated significantly more often in Group 2. In LS tumors, the degree of hypermutability exceeded that of the hypermutated CA-CRC Groups 1 and 2, and somatic mutational profiles and signatures were different. In conclusion, Groups 1 (4%) and 3 (63%) comply with published studies, whereas Group 2 (33%) is novel. The existence of molecularly distinct subgroups within CA-CRC may guide clinical management, such as therapy options.

The Synthetic Small Molecule FL3 Combats Intestinal Tumorigenesis via Axin1-Mediated Inhibition of Wnt/β-Catenin Signaling

Colorectal cancer exhibits aberrant activation of Wnt/β-catenin signaling. Many inhibitors of the Wnt/β-catenin pathway have been tested for Wnt-dependent cancers including colorectal cancer, but are unsuccessful due to severe adverse reactions. FL3 is a synthetic derivative of natural products called flavaglines, which exhibit anti-inflammatory and cytoprotective properties in intestinal epithelial cells, but has not been previously tested in cell or preclinical models of intestinal tumorigenesis. In vitro studies suggest that flavaglines target prohibitin 1 (PHB1) as a ligand, but this has not been established in the intestine. PHB1 is a highly conserved protein with diverse functions that depend on its posttranslational modifications and subcellular localization. Here, we demonstrate that FL3 combats intestinal tumorigenesis in the azoxymethane-dextran sodium sulfate and Apc^Min/+ mouse models and in human colorectal cancer tumor organoids (tumoroids) by inhibiting Wnt/β-catenin signaling via induction of Axin1 expression. FL3 exhibited no change in cell viability in normal intestinal epithelial cells or human matched-normal colonoids. FL3 response was diminished in colorectal cancer cell lines and human colorectal cancer tumoroids harboring a mutation at S45 of β-catenin. PHB1 deficiency in mice or in human colorectal cancer tumoroids abolished FL3-induced expression of Axin1 and drove tumoroid death. In colorectal cancer cells, FL3 treatment blocked phosphorylation of PHB1 at Thr258, resulting in its nuclear translocation and binding to the Axin1 promoter. These results suggest that FL3 inhibits Wnt/β-catenin signaling via PHB1-dependent activation of Axin1. FL3, therefore, represents a novel compound that combats Wnt pathway-dependent cancers, such as colorectal cancer. SIGNIFICANCE: Targeting of PHB1 by FL3 provides a novel mechanism to combat Wnt-driven cancers, with limited intestinal toxicity. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/17/3519/F1.large.jpg.

Decitabine attenuates dextran sodium sulfate‑induced ulcerative colitis through regulation of immune regulatory cells and intestinal barrier

To investigate the effect of decitabine on the regulation of intestinal barrier function in mice with inflammatory bowel disease, an experimental model of colitis was established via drinking water with dextran sulfate sodium (DSS). Hematoxylin and eosin staining was used to observe the pathological changes of the colon. Cytokine production was measured by an ELISA assay. Flow cytometry was used to measure the level of regulatory T cells. Immunofluorescence, immunohistochemistry and western blot analyses detected the protein expression and distribution in colon tissue. Following the administration of decitabine, the symptoms of intestinal inflammation in the mice were significantly relieved; the expression of IL-17 was decreased, and the levels of TGF-β and IL-10 were increased. In addition, the induction of forkhead box P3 (Foxp3) in naive T cells increased the proportion of CD4⁺ Foxp3⁺ T cells in CD4⁺ T cells. Furthermore, decitabine increased the levels of zonular occludens-1 and occludin, and inhibited the phosphorylation of ERK1/2, JNK and p38. In conclusion, the present study suggested that decitabine could alleviate DSS-induced impaired colon barrier and the weight loss, mucus and bloody stools in mice by releasing the inhibitory factor IL-10, reducing the pro-inflammatory factor IL-17, activating CD4⁺ Foxp3⁺ T cells and inhibiting the activation of the MAPK pathway.

From Genetics to Epigenetics, Roles of Epigenetics in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a destructive, recurrent, and heterogeneous disease. Its detailed pathogenesis is still unclear, although available evidence supports that IBD is caused by a complex interplay between genetic predispositions, environmental factors, and aberrant immune responses. Recent breakthroughs with regard to its genetics have offered valuable insights into the sophisticated genetic basis, but the identified genetic factors only explain a small part of overall disease variance. It is becoming increasingly apparent that epigenetic factors can mediate the interaction between genetics and environment, and play a fundamental role in the pathogenesis of IBD. This review outlines recent genetic and epigenetic discoveries in IBD, with a focus on the roles of epigenetics in disease susceptibility, activity, behavior and colorectal cancer (CRC), and their potential translational applications.

Weak Cytotoxic T Cells Activation Predicts Low-Grade Dysplasia Persistence in Ulcerative Colitis

In patients with ulcerative colitis (UC), dysplasia develops in 10%–20% of cases. The persistence of low-grade dysplasia (LGD) in UC in 2 consecutive observations is still an indication for restorative proctocolectomy. Our hypothesis is that in the case of weak cytotoxic activation, dysplasia persists. We aimed to identify possible immunological markers of LGD presence and persistence.

The study of methylation and single nucleotide polymorphisms of cancer-related genes in patients with early-stage ulcerative colitis

Aim: To investigate the methylation status and single nucleotide polymorphisms (SNPs) of cancer-associated genes in ulcerative colitis (UC) patients and explore the potential mechanism for high cancer risk of UC. Methods: A total of 103 patients were enrolled in our study, which included 30 healthy subjects, 41 patients with early-stage UC, and 32 patients with colorectal cancer (CRC). Methylation status of cyclooxygenase 2 (COX2) and human RUNT-related transcription factor 3 (RUNX3) genes in colonic mucosa from 3 groups of subjects were detected by methylation-specific polymerase chain reaction (PCR). The SNPs TNF-α rs1800629 and IL-1 rs1143627 were genotyped by PCR and direct sequencing. Results: The methylation rate of RUNX3 gene within CRC group was 35.7%, which was significantly higher than the other two groups (Healthy control 5.9%, UC 15.4%, p = .040). There was no significant difference in the methylation rate of RUNX3 between early-stage UC group and healthy control group (p = .633). The methylation rate of COX2 gene, the genotypes (GG, AG) and alleles (A, G) of rs1800629, and the genotypes (CC,CT,TT) and alleles (C,T) of rs1143627 were not statistically different among three groups. Conclusion: In the early stage of UC, the methylation rate of cancer-related genes RUNX3 and COX2 and SNPs TNF-α rs1800629 and IL-1 rs1143627 were not significantly different compared with healthy subjects. The methylation rate of RUNX3 in CRC increased, while the methylation rate of COX2 and SNPs TNF-α rs1800629 and IL-1 rs1143627 did not change significantly compared with the other two groups.

New Methylation Biomarker Panel for Early Diagnosis of Dysplasia or Cancer in High-Risk Inflammatory Bowel Disease Patients

BACKGROUND

The risk of developing colorectal cancer (CRC) is increased in patients with inflammatory bowel disease (IBD) of the colon. The aim of the study was to evaluate the effectiveness of selected methylation gene panel for the early detection of CRC in high-risk IBD patients.

METHODS

In a discovery phase, 73 biopsies of 48 IBD patients (associated or not to CRC) were analyzed from genome-wide DNA methylation analysis using the Illumina Human Methylation 450K BeadChip. The panel of 5 genes selected (EYA4, SLIT2, FLI1, USP44, and SND1) was validated prospectively using methylation-specific melting curve analysis in biopsies of diseased and adjacent healthy tissue of 203 patients: 38 with IBD and associated neoplasia, 81 patients with IBD (25 of them with high risk), 48 with sporadic CRC, and 36 healthy controls.

RESULTS

The prevalence of methylation was higher in patients with IBD and associated neoplasia (both in diseased and adjacent healthy tissue, 71% and 52%, respectively) than in healthy controls (2/36, 6%; P = 6.72E-05). Methylation in IBD patients at high risk of dysplasia or cancer was more frequently detected than in patients at low risk (92% vs 57%; odds ratio, 8.63; P = 0.001). EYA4 and SLIT2 were the markers most frequently methylated. Differences in methylation levels were more evident in healthy mucosa (82% vs 15% high vs low risk, respectively; P = 1.25E-05).

CONCLUSIONS

Analysis of this panel of methylation markers may help in the early identification of colorectal dysplasia or cancer in high-risk IBD patients.

An Overview of Molecular Profiles in Ulcerative Colitis-Related Cancer

Ulcerative colitis (UC) is an independent risk factor of colorectal cancer (CRC). Both genetic and epigentic events induce a unique molecular profile during the development from UC to UC-related CRC (UCRC). These molecular changes play varied roles in DNA repair, immune response, cell metabolism, and interaction with the microbiota during the carcinogenesis process. This review will systmatically discuss the molecular characteristics of UCRC and point out the future perspectives in this research field.

Increased Genetic Instability and Accelerated Progression of Colitis-Associated Colorectal Cancer through Intestinal Epithelium-specific Deletion of Klf4

Krüppel-like factor 4 (KLF4), a zinc finger transcription factor, regulates homeostasis of the intestinal epithelium. Previously, it was reported that KLF4 functions as a tumor suppressor in colorectal cancer. Here, evidence demonstrates that KLF4 mitigates the development and progression of colitis-associated colorectal cancer (CAC) in a murine model. Mice with intestinal epithelium-specific deletion of Klf4 (Klf4^ΔIS ) and control mice (Klf4^fl/fl ) were used to explore the role of KLF4 in the development of azoxymethane (AOM) and dextran sodium sulfate (DSS)-induced CAC. Upon AOM and DSS treatment, KLF4 expression was progressively lost in colonic tissues of Klf4^fl/fl mice during tumor development. Klf4^ΔIS mice treated with AOM/DSS developed significantly more adenomatous polyps and carcinomas in situ in comparison with treated Klf4^fl/fl mice. Adenomatous polyps, but not normal-appearing mucosa, from colonic tissues of treated Klf4^ΔIS mice contained a significantly increased number of mitotic cells with more than 2 centrosomes relative to treated control mice. KLF4 and p53 colocalize to the centrosomes in mouse embryonic fibroblasts (MEF). Absence of KLF4 in Klf4^-/- MEFs inhibits and its overexpression restores p53 localization to the centrosomes in Klf4^-/- MEFs. IMPLICATIONS: Taken together, these results indicate that KLF4 plays a protective role against progression of CAC by guarding against genetic instability.

Early detection of ulcerative colitis-associated colorectal cancer

Colitis-associated colorectal cancer (CACC) is one of the most serious complications of inflammatory bowel disease (IBD), particularly in ulcerative colitis (UC); it accounts for approximately 15% of all-causes mortality among IBD patients. Because CACC shows a worse prognosis and higher mortality than sporadic colorectal cancer, early detection is critical. Colonoscopy is primarily recommended for surveillance and several advanced endoscopic imaging techniques are emerging. In addition, recent studies have reported on attempts to develop clinically relevant biomarkers for surveillance using various biosamples, which may become high-performance screening tools in the future, so the best approach and technique for cancer surveillance in long-standing UC patients remain under debate. This review gives a comprehensive description and summary about what progress has been made in terms of early CACC detection.

The combination of indirubin and isatin attenuates dextran sodium sulfate induced ulcerative colitis in mice

Indirubin and isatin have been used in the treatment of inflammatory diseases due to their anti-inflammatory properties. This study aimed to evaluate the combined effect of indirubin and isatin on dextran sulfate sodium (DSS)-induced ulcerative colitis (UC). UC was induced by the administration of 3% (w/v) DSS solution, and then the model mice were administered indirubin (10 mg/kg body mass) and (or) isatin (10 mg/kg body mass) by gavage once daily for 7 days. The results showed that indirubin and isatin, individually or combined, significantly inhibited weight loss, lowered disease activity index (DAI), ameliorated pathological changes, decreased the levels of pro-inflammatory mediators and myeloperoxidase (MPO) activity, increased the expression of anti-inflammatory cytokines and Foxp3, suppressed CD4⁺ T cell infiltration, and inhibited oxidative stress and epithelial cell apoptosis. Additionally, indirubin and isatin, both individually and combined, can also inhibit activation of the NF-κB and MAPK pathways induced by DSS. The protective effect of combination therapy against UC was superior to that of single-agent treatment. These results suggest that indirubin combined with isatin attenuates DSS-induced UC, and changes to the NF-κB and MAPK signaling pathways may mediate the protective effects of indirubin and isatin in UC.

Aberrant Methylation of T-cadherin Can Be a Diagnostic Biomarker for Colorectal Cancer

BACKGROUND/AIM

T-cadherin is a tumor suppressor gene, its predictive value in colorectal cancer (CRC) still remains controversial. In this study, we aimed to evaluate the association between T-cadherin promoter methylation and CRC by performing a meta-analysis.

MATERIALS AND METHODS

The relevant literature was searched using the PubMed, Cochrane Library, Web of Science and Google Scholar databases for articles published until December 2016. The effect sizes were estimated by measuring an odds ratio (OR) with a 95% confidence interval (CI). Sensitivity analysis was performed to examine the heterogeneity and funnel plots were constructed to evaluate publication bias.

RESULTS

Nine studies, including 488 samples were included in this meta-analysis. The pooled OR of T-cadherin promoter methylation in cancer tissues was 16.73 (95%CI=6.24-44.87), 19.48 (95%CI=5.64-67.31) and 2.23 (95%CI=1.05-4.75) compared to normal tissues, adjacent tissues and premalignant tissues, respectively. The relationship between T-cadherin promoter methylation and clinicopathological features were also analyzed. However, a significant association was not observed between T-cadherin promoter methylation status and gender, tumor stage, and lymph node status (p>0.05).

CONCLUSION

The methylation status of T-cadherin promoter was strongly associated with CRC risk. However, T-cadherin promoter methylation may have a limited prognostic value for CRC patients.

Epigenetic and epitranscriptomic changes in colorectal cancer: Diagnostic, prognostic, and treatment implications

A cancer cell is the final product of a complex mixture of genetic, epigenetic and epitranscriptomic alterations, whose final interplay contribute to cancer onset and progression. This is specifically true for colorectal cancer, a tumor with a strong epigenetic component, which acts earlier than any other genetic alteration in promoting cancer cell malignant transformation. The pattern of progressive, and usually subtype-specific, DNA and histone modifications that occur in colorectal cancer has been extensively studied in the last decade, providing plenty of data to explore. For this tumor, it became recently evident that also RNA modifications play a relevant role in the activation of oncogenes or repression of tumor suppressor genes. In this review we provide a brief overview of all epigenetic and epitranscriptomic changes that have been found associated to colorectal cancer till now. We explore the impact of these alterations in cancer prognosis and response to treatment and discuss their potential use as cancer biomarkers.

Screening of exon methylation biomarkers for colorectal cancer via LC-MS/MS strategy

The identification of biomarkers would be of benefit for the diagnosis and treatment of colorectal cancer. DNA methylation in specific genomic regions, which had shown strongly association with disease genotypes, was an effective indicator to reveal the occurrence and development of cancers. To screen out methylation biomarkers for colorectal cancer (CRC), genomic DNA was isolated from colorectal cancerous and corresponding cancer-adjacent tissues collected from 30 CRC patients and then bisulfite-converted. The exon regions of 5 targeted genes (CNRIP1, HIC1, RUNX3, p15, and SFRP2) were amplified by using nested polymerase chain reaction with specific primers, and the amplicon was purified and hydrolyzed. The methylation levels of these specific regions were detected by liquid chromatography tandem mass spectrometry (LC-MS/MS). The results showed that 5 targeted exon regions were successfully amplified and confirmed by sequencing. The methodological validations indicated that LC-MS/MS was highly sensitive and accurate. The methylation levels of CNRIP1 and RUNX3 were remarkably high in CRC tissues with statistical difference when compared with corresponding cancer-adjacent individuals, while that of HIC1, p15, and SFRP2 had no difference between 2 subjects. These findings supported CNRIP1 and RUNX3 as potential DNA methylation biomarkers for CRC diagnosis and treatment, and our LC-MS/MS approach exhibited great advantages in the identification of regional DNA methylation biomarkers.

DNA methylation patterns in ulcerative colitis-associated cancer: a systematic review

BACKGROUND

Evidence points to the role of DNA methylation in ulcerative colitis (UC)-associated cancer (UCC), the most serious complication of ulcerative colitis. A better understanding of the etiology of UCC may facilitate the development of new therapeutic targets and help to identify biomarkers of the disease risk.

METHODS

A search was performed in three databases following PRISMA protocol. DNA methylation in UCC was compared with sporadic colorectal cancer (SCRC), and individual genes differently methylated in UCC identified.

RESULTS

While there were some similarities in the methylation patterns of UCC compared with SCRC, generally lower levels of hypermethylation in promoter regions of individual genes was evident in UCC. Certain individual genes are, however, highly methylated in colitis-associated cancer: RUNX3, MINT1, MYOD and p16 exon1 and the promoter regions of EYA4 and ESR.

CONCLUSION

Patterns of DNA methylation differ between UCC and SCRC. Seven genes appear to be promising putative biomarkers.

Adiponectin and Intelectin-1: Important Adipokine Players in Obesity-Related Colorectal Carcinogenesis

Overweight is believed to be associated with colorectal cancer risk. Adipose tissue is loose connective tissue composed of adipocytes. It is now recognized as a major endocrine organ, secreting humoral factors collectively called adipokines. Aberrant hormonal systems consisting of modulated adipokines and their receptors are thought to play a role in colorectal carcinogenesis and cancer progression in obese conditions. However, it is still unclear whether and how each adipokine relates to colorectal carcinogenesis. Notably, a couple of molecules that were initially proposed to be obesity-related adipokines were disqualified by subsequent studies. The adipokines, adiponectin, and intelectin-1 (also known as omentin-1), whose levels are decreased in obesity, act as tumor suppressor factors in various cancers. Numerous studies have demonstrated a link between the insufficient expression and function of adiponectin and its receptor, T-cadherin, in colorectal carcinogenesis. Moreover, our recent study indicated that loss of TMEM207, which is critical for the proper processing of intelectin-1 in the colon mucosa, leads to insufficient intelectin-1 production, thus participating in colorectal carcinogenesis. Here, we discuss the recent understanding of the role of adipokines in colorectal carcinogenesis and subsequently describe the potent tumor suppressor roles of intelectin-1 and TMEM207 in colorectal cancer.

Adiponectin and Intelectin-1: Important Adipokine Players in Obesity-Related Colorectal Carcinogenesis

Overweight is believed to be associated with colorectal cancer risk. Adipose tissue is loose connective tissue composed of adipocytes. It is now recognized as a major endocrine organ, secreting humoral factors collectively called adipokines. Aberrant hormonal systems consisting of modulated adipokines and their receptors are thought to play a role in colorectal carcinogenesis and cancer progression in obese conditions. However, it is still unclear whether and how each adipokine relates to colorectal carcinogenesis. Notably, a couple of molecules that were initially proposed to be obesity-related adipokines were disqualified by subsequent studies. The adipokines, adiponectin, and intelectin-1 (also known as omentin-1), whose levels are decreased in obesity, act as tumor suppressor factors in various cancers. Numerous studies have demonstrated a link between the insufficient expression and function of adiponectin and its receptor, T-cadherin, in colorectal carcinogenesis. Moreover, our recent study indicated that loss of TMEM207, which is critical for the proper processing of intelectin-1 in the colon mucosa, leads to insufficient intelectin-1 production, thus participating in colorectal carcinogenesis. Here, we discuss the recent understanding of the role of adipokines in colorectal carcinogenesis and subsequently describe the potent tumor suppressor roles of intelectin-1 and TMEM207 in colorectal cancer.

Role of CDH13 promoter methylation in the carcinogenesis, progression, and prognosis of colorectal cancer: A systematic meta-analysis under PRISMA guidelines

BACKGROUND

H-cadherin (CDH13) is commonly downregulated through promoter methylation in various cancers. However, the role of CDH13 promoter methylation status in patients with colorectal cancer (CRC) remains to be clarified.

METHODS

Eligible articles were identified from online electronic database based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement criteria. The pooled odds ratio (OR) and the corresponding 95% confidence interval (95% CI) were calculated and analyzed.

RESULTS

Eventually, a total of nine studies were included in this meta-analysis, including 488 CRC, 298 adjacent, 144 normal, 68 premalignant tissues. The results demonstrated that CDH13 promoter methylation was notably higher in CRC than in normal, adjacent, and premalignant tissues (cancer tissues vs normal tissues: OR = 16.94, P < 0.001; cancer tissues vs adjacent tissues: OR = 20.06, P < 0.001; cancer tissues vs premalignant tissues: OR = 2.23, P = 0.038). CDH13 promoter methylation had a significantly increased risk for poorly differentiated CRC (OR = 4.07, P = 0.001). CDH13 promoter methylation was not associated with sex status, tumor stage, and lymph node status (all P > 0.05). One study with 85 CRC patients reported that CDH13 promoter methylation was correlated with poor prognosis in overall survival (OS).

CONCLUSIONS

CDH13 promoter methylation may play an important role in the initiation and progression of CRC, and may be correlated with OS of patients with CRC. Additional studies with large sample sizes are needed to further confirm our findings in the future.

Predictive and prognostic biomarkers in colorectal cancer: A systematic review of recent advances and challenges

BACKGROUND

Colorectal cancer (CRC) is one of the leading cause of cancer deaths worldwide. Since CRC is largely asymptomatic until alarm features develop to advanced stages, the implementation of the screening programme is very much essential to reduce cancer incidence and mortality rates. CRC occurs predominantly from accumulation of genetic and epigenetic changes in colon epithelial cells, which later gets transformed into adenocarcinomas.

SCOPE OF REVIEW

The current challenges of screening paradigm and diagnostic ranges are from semi-invasive methods like colonoscopy to non-invasive stool-based test, have resulted in over-diagnosis and over-treatment of CRC. Hence, new screening initiatives and deep studies are required for early diagnosis of CRC. In this regard, we not only summarise current predictive and prognostic biomarkers with their potential for diagnostic and therapeutic applications, but also describe current limitations, future perspectives and challenges associated with the progression of CRC.

MAJOR CONCLUSIONS

Currently many potential biomarkers have already been successfully translated into clinical practice eg. Fecal haemoglobin, Carcinoembryonic antigen (CEA) and CA19.9, although these are not highly promising diagnostic target for personalized medicine. So there is a critical need for reliable, minimally invasive, highly sensitive and specific genetic markers of an individualised and optimised patient treatment at the earliest disease stage possible.

GENERAL SIGNIFICANCE

Identification of a new biomarker, or a set of biomarkers to the development of a valid, and clinical sensible assay that can be served as an alternative tool for early diagnosis of CRC and open up promising new targets in therapeutic intervention strategies.

Peperomin E reactivates silenced tumor suppressor genes in lung cancer cells by inhibition of DNA methyltransferase

Advanced lung cancer has poor prognosis owing to its low sensitivity to current chemotherapy agents. Therefore, discovery of new therapeutic agents is urgently needed. In this study, we investigated the antitumor effects of peperomin E, a secolignan isolated from Peperomia dindygulensis, a frequently used Chinese folk medicine for lung cancer treatment. The results indicate that peperomin E has antiproliferative effects, promoting apoptosis and cell cycle arrest in non‐small‐cell lung cancer (NSCLC) cell lines in a dose‐dependent manner, while showing lower toxicity against normal human lung epidermal cells. Peperomin E inhibited tumor growth in A549 xenograft BALB/c nude mice without significant secondary adverse effects, indicating that it may be safely used to treat NSCLC. Furthermore, the mechanisms underlying the anticancer effects of peperomin E have been investigated. Using an in silico target fishing method, we observed that peperomin E directly interacts with the active domain of DNA methyltransferase 1 (DNMT1), potentially affecting its genome methylation activity. Subsequent experiments verified that peperomin E decreased DNMT1 activity and expression, thereby decreasing global methylation and reactivating the epigenetically silenced tumor suppressor genes including RASSF1A,APC,RUNX3, and p16INK4, which in turn activates their mediated pro‐apoptotic and cell cycle regulatory signaling pathways in lung cancer cells. The observations herein report for the first time that peperomin E is a potential chemotherapeutic agent for NSCLC. The anticancer effects of peperomin E may be partly attributable to its ability to demethylate and reactivate methylation‐silenced tumor suppressor genes through direct inhibition of the activity and expression of DNMT1.

Epigenetic regulation of active Chinese herbal components for cancer prevention and treatment: A follow-up review

Epigenetic modifications include DNA methylation, histone modification, and other patterns. These processes are associated with carcinogenesis and cancer progression. Thus, epigenetic modification-related enzymes, such as DNA methyltransferases (DNMTs), histone methyltransferases (HMTs), histone demethylases (HDMTs), histone acetyltransferases (HATs), and histone deacetylases (HDACs), as well as some related proteins, including methyl-CpG binding proteins (MBPs) and DNMT1-associated protein (DMAP 1), are considered as potential targets for cancer prevention and therapy. Numerous natural compounds, mainly derived from Chinese herbs and chemically ranging from polyphenols and flavonoids to mineral salts, inhibit the growth and development of various cancers by targeting multiple genetic and epigenetic alterations. This review summarizes the epigenetic mechanisms by which active compounds from Chinese herbs exert their anti-cancer effect. A subset of these compounds, such as curcumin and resveratrol, affect multiple epigenetic processes, including DNMT inhibition, HDAC inactivation, MBP suppression, HAT activation, and microRNA modulation. Other compounds also regulate epigenetic modification processes, but the underlying mechanisms and clear targets remain unknown. Accordingly, further studies are required.