DNA methylation patterns in blood of patients with colorectal cancer and adenomatous colorectal polyps

Pathogenesis and biomarkers of colorectal cancer by epigenetic alteration

Colorectal cancer (CRC) ranks third in cancer incidence and stands as the second leading cause of cancer-related deaths globally. CRC tumorigenesis results from a cumulative set of genetic and epigenetic alterations, disrupting cancer-regulatory processes like cell proliferation, metabolism, angiogenesis, cell death, invasion, and metastasis. Key epigenetic modifications observed in cancers encompass abnormal DNA methylation, atypical histone modifications, and irregularities in noncoding RNAs, such as microRNAs and long noncoding RNAs. The advancement in genomic technologies has positioned these genetic and epigenetic shifts as potential clinical biomarkers for CRC patients. This review concisely covers the fundamental principles of CRC-associated epigenetic changes, and examines in detail their emerging role as biomarkers for early detection, prognosis, and treatment response prediction.

Unlocking the potential of tumor-derived DNA in urine for cancer detection: methodological challenges and opportunities

High cancer mortality rates and the rising cancer burden worldwide drive the development of innovative methods in order to advance cancer diagnostics. Urine contains a viable source of tumor material and allows for self-collection from home. Biomarker testing in this liquid biopsy represents a novel approach that is convenient for patients and can be effective in detecting cancer at a curable stage. Here, we set out to provide a detailed overview of the rationale behind urine-based cancer detection, with a focus on non-urological cancers, and its potential for cancer diagnostics. Moreover, evolving methodological challenges and untapped opportunities for urine biomarker testing are discussed, particularly emphasizing DNA methylation of tumor-derived cell-free DNA. We also provide future recommendations for technical advancements in urine-based cancer detection and elaborate on potential mechanisms involved in the transrenal transport of cell-free DNA.

DNA methylation modulates epigenetic regulation in colorectal cancer diagnosis, prognosis and precision medicine

Colorectal cancer (CRC) is a multifaceted disease influenced by the interplay of genetic and environmental factors. The clinical heterogeneity of CRC cannot be attributed exclusively to genetic diversity and environmental exposures, and epigenetic markers, especially DNA methylation, play a critical role as key molecular markers of cancer. This review compiles a comprehensive body of evidence underscoring the significant involvement of DNA methylation modifications in the pathogenesis of CRC. Moreover, this review explores the potential utility of DNA methylation in cancer diagnosis, prognostics, assessment of disease activity, and prediction of drug responses. Recognizing the impact of DNA methylation will enhance the ability to identify distinct CRC subtypes, paving the way for personalized treatment strategies and advancing precision medicine in the management of CRC.

Pan-precancer and cancer DNA methylation profiles revealed significant tissue specificity of interrupted biological processes in tumorigenesis

DNA methylation (DNAme) alterations are known to initiate from the precancerous stage of tumorigenesis. Herein, we investigated the global and local patterns of DNAme perturbations in tumorigenesis by analysing the genome-wide DNAme profiles of the cervix, colorectum, stomach, prostate, and liver at precancerous and cancer stages. We observed global hypomethylation in tissues of both two stages, except for the cervix, whose global DNAme level in normal tissue was lower than that of the other four tumour types. For alterations shared by both stages, there were common hyper-methylation (sHyperMethyl) and hypo-methylation (sHypoMethyl) changes, of which the latter type was more frequently identified in all tissues. Biological pathways interrupted by sHyperMethyl and sHypoMethyl alterations demonstrated significant tissue specificity. DNAme bidirectional chaos indicated by the enrichment of both sHyperMethyl and sHypoMethyl changes in the same pathway was observed in most tissues and was a common phenomenon, particularly in liver lesions. Moreover, for the same enriched pathways, different tissues may be affected by distinct DNAme types. For the PI3K-Akt signalling pathway, sHyperMethyl enrichment was observed in the prostate dataset, but sHypoMethyl enrichment was observed in the colorectum and liver datasets. Nevertheless, they did not show an increased possibility in survival prediction of patients in comparison with other DNAme types. Additionally, our study demonstrated that gene-body DNAme changes of tumour suppressor genes and oncogenes may persist from precancerous lesions to the tumour. Overall, we demonstrate the tissue specificity and commonality of cross-stage alterations in DNA methylation profiles in multi-tissue tumorigenesis.

Current advances in detecting genetic and epigenetic biomarkers of colorectal cancer

Colorectal carcinoma (CRC) is the third most common cancer in terms of diagnosis and the second in terms of mortality. Recent studies have shown that various proteins, extracellular vesicles (i.e., exosomes), specific genetic variants, gene transcripts, cell-free DNA (cfDNA), circulating tumor DNA (ctDNA), microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and altered epigenetic patterns, can be used to detect, and assess the prognosis of CRC. Over the last decade, a plethora of conventional methodologies (e.g., polymerase chain reaction [PCR], direct sequencing, enzyme-linked immunosorbent assay [ELISA], microarray, in situ hybridization) as well as advanced analytical methodologies (e.g., microfluidics, electrochemical biosensors, surface-enhanced Raman spectroscopy [SERS]) have been developed for analyzing genetic and epigenetic biomarkers using both optical and non-optical tools. Despite these methodologies, no gold standard detection method has yet been implemented that can analyze CRC with high specificity and sensitivity in an inexpensive, simple, and time-efficient manner. Moreover, until now, no study has critically reviewed the advantages and limitations of these methodologies. Here, an overview of the most used genetic and epigenetic biomarkers for CRC and their detection methods are discussed. Furthermore, a summary of the major biological, technical, and clinical challenges and advantages/limitations of existing techniques is also presented.

Colon cancer transcriptome

Over the last four decades, methodological innovations have continuously changed transcriptome profiling. It is now feasible to sequence and quantify the transcriptional outputs of individual cells or thousands of samples using RNA sequencing (RNA-seq). These transcriptomes serve as a connection between cellular behaviors and their underlying molecular mechanisms, such as mutations. This relationship, in the context of cancer, provides a chance to unravel tumor complexity and heterogeneity and uncover novel biomarkers or treatment options. Since colon cancer is one of the most frequent malignancies, its prognosis and diagnosis seem to be critical. The transcriptome technology is developing for an earlier and more accurate diagnosis of cancer which can provide better protectivity and prognostic utility to medical teams and patients. A transcriptome is a whole set of expressed coding and non-coding RNAs in an individual or cell population. The cancer transcriptome includes RNA-based changes. The combined genome and transcriptome of a patient may provide a comprehensive picture of their cancer, and this information is beginning to affect treatment decision-making in real-time. A full assessment of the transcriptome of colon (colorectal) cancer has been assessed in this review paper based on risk factors such as age, obesity, gender, alcohol use, race, and also different stages of cancer, as well as non-coding RNAs like circRNAs, miRNAs, lncRNAs, and siRNAs. Similarly, they have been examined independently in the transcriptome study of colon cancer.

Using Circulating Tumor DNA as a Novel Biomarker to Screen and Diagnose Colorectal Cancer: A Meta-Analysis

(1) Background: Circulating tumor DNA (ctDNA) has emerged as a promising biomarker for many kinds of tumors. However, whether ctDNA could be an accurate diagnostic biomarker in colorectal cancer (CRC) remains to be clarified. The aim of this study was to evaluate the diagnostic accuracy of ctDNA in CRC. (2) Methods: PubMed, Web of Science, and Cochrane databases were searched to identify studies reporting the use of ctDNA to screen and diagnose CRC, and all relevant studies published until October 2022 were enrolled for our analysis. These studies were divided into three primer subgroups: the subgroup of quantitative or qualitative analysis of ctDNA and the subgroup of septin9 (SEPT9) methylation assay. (3) Results: A total of 79 qualified articles with 25,240 subjects were incorporated into our meta-analysis. For quantitative studies, the combined sensitivity (SEN), specificity (SPE), and diagnostic odds ratio (DOR) were 0.723 (95% CI: 0.623-0.803), 0.920 (95% CI: 0.827-0.966), and 23.305 (95% CI: 9.378-57.906), respectively, yielding an AUC of 0.860. The corresponding values for qualitative studies were 0.610 (95% CI: 0.566-0.651), 0.891 (95% CI: 0.878-0.909), 12.569 (95% CI: 9.969-15.848), and 0.823, respectively. Detection of SEPT9 methylation depicted an AUC of 0.879, with an SEN of 0.679 (95% CI: 0.622-0.732), an SPE of 0.903 (95% CI: 0.878-0.923), and a DOR of 20.121 (95% CI:14.404-28.106), respectively. (4) Conclusion: Blood-based ctDNA assay would be a potential novel biomarker for CRC screening and diagnosis. Specifically, quantitative analysis of ctDNA or qualitative analysis of SEPT9 methylation exhibited satisfying diagnostic efficiency. Larger sample studies are needed to further confirm our conclusions and to make the ctDNA approach more sensitive and specific.

Association of colorectal cancer with genetic and epigenetic variation in PEAR1—A population-based cohort study

Platelet Endothelial Aggregation Receptor 1 (PEAR1) modulates angiogenesis and platelet contact-induced activation, which play a role in the pathogenesis of colorectal cancer. We therefore tested the association of incident colorectal cancer and genetic and epigenetic variability in PEAR1 among 2532 randomly recruited participants enrolled in the family-based Flemish Study on Environment, Genes and Health Outcomes (51.2% women; mean age 44.8 years). All underwent genotyping of rs12566888 located in intron 1 of the PEAR1 gene; in 926 participants, methylation at 16 CpG sites in the PEAR1 promoter was also assessed. Over 18.1 years (median), 49 colorectal cancers occurred, all in different pedigrees. While accounting for clustering of risk factors within families and adjusting for sex, age, body mass index, the total-to-HDL cholesterol ratio, serum creatinine, plasma glucose, smoking and drinking, use of antiplatelet and nonsteroidal anti-inflammatory drug, the hazard ratio of colorectal cancer contrasting minor-allele (T) carriers vs. major-allele (GG) homozygotes was 2.17 (95% confidence interval, 1.18–3.99; P = 0.013). Bootstrapped analyses, from which we randomly excluded from two to nine cancer cases, provided confirmatory results. In participants with methylation data, we applied partial least square discriminant analysis (PLS-DA) and identified two methylation sites associated with higher colorectal cancer risk and two with lower risk. In-silico analysis suggested that methylation of the PEAR1 promoter at these four sites might affect binding of transcription factors p53, PAX5, and E2F-1, thereby modulating gene expression. In conclusion, our findings suggest that genetic and epigenetic variation in PEAR1 modulates the risk of colorectal cancer in white Flemish. To what extent, environmental factors as exemplified by our methylation data, interact with genetic predisposition and modulate penetrance of colorectal cancer risk is unknown.

DNA methylation-based diagnostic, prognostic, and predictive biomarkers in colorectal cancer

DNA methylation is an epigenetic mechanism regulating gene expression. Changes in DNA methylation were suggested to be useful biomarkers for diagnosis, and for the determination of prognosis and treatment response. Here, we provide an overview of methylation-based biomarkers in colorectal cancer. First, we start with the two methylation-based diagnostic biomarkers already approved for colorectal cancer, SEPT9 and the combination of NDRG4 and BMP3. Then, we provide a list-based overview of new biomarker candidates depending on the sample source including plasma, stool, urine, and surgically removed tumor tissues. The most often identified markers like SDC2, VIM, APC, MGMT, SFRP1, SFRP2, and NDRG4 have distinct functions previously linked to tumor progression. Although numerous studies have identified tumor-specific methylation changes, most of these alterations were observed in a single study only. The lack of validation in independent samples means low reproducibility and is a major limitation. The genome-wide determination of methylation status (methylome) can provide data to solve these issues. In the third section of the review, methylome studies focusing on different aspects related to CRC, including precancerous lesions, CRC-specific changes, molecular subtypes, aging, and chemotherapy response are summarized. Notably, techniques simultaneously analyzing a large set of regions can also uncover epigenetic regulation of genes which have not yet been associated with tumorigenesis previously. A remaining constraint of studies published to date is the low patient number utilized in these preventing the identification of clinically valuable biomarker candidates. Either future large-scale studies or the integration of already available methylome-level data will be necessary to uncover biomarkers sufficiently robust for clinical application.

Novel Methylation Biomarkers for Colorectal Cancer Prognosis

Colorectal cancer (CRC) comprises the third most common cancer worldwide and the second regarding number of deaths. In order to make a correct and early diagnosis to predict metastasis formation, biomarkers are an important tool. Although there are multiple signaling pathways associated with cancer progression, the most recognized are the MAPK pathway, p53 pathway, and TGF-β pathway. These pathways regulate many important functions in the cell, such as cell cycle regulation, proliferation, differentiation, and metastasis formation, among others. Changes in expression in genes belonging to these pathways are drivers of carcinogenesis. Often these expression changes are caused by mutations; however, epigenetic changes, such as DNA methylation, are increasingly acknowledged to play a role in the deregulation of oncogenic genes. This makes DNA methylation changes an interesting biomarkers in cancer. Among the newly identified biomarkers for CRC metastasis INHBB, SMOC2, BDNF, and TBRG4 are included, all of which are highly deregulated by methylation and closely associated with metastasis. The identification of such biomarkers in metastasis of CRC may allow a better treatment and early identification of cancer formation in order to perform better diagnostics and improve the life expectancy.

Updates on liquid biopsy: current trends and future perspectives for clinical application in solid tumors

Despite advances in screening and therapeutics cancer continues to be one of the major causes of morbidity and mortality worldwide. The molecular profile of tumor is routinely assessed by surgical or bioptic samples, however, genotyping of tissue has inherent limitations: it represents a single snapshot in time and it is subjected to spatial selection bias owing to tumor heterogeneity. Liquid biopsy has emerged as a novel, non-invasive opportunity of detecting and monitoring cancer in several body fluids instead of tumor tissue. Circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), RNA (mRNA and microRNA), microvesicles, including exosomes and tumor "educated platelets" were recently identified as a source of genomic information in cancer patients which could reflect all subclones present in primary and metastatic lesions allowing sequential monitoring of disease evolution. In this review, we summarize the currently available information concerning liquid biopsy in breast cancer, colon cancer, lung cancer and melanoma. These promising issues still need to be standardized and harmonized across laboratories, before fully adopting liquid biopsy approaches into clinical practice.

Cell free DNA as an evolving liquid biopsy biomarker for initial diagnosis and therapeutic nursing in Cancer- An evolving aspect in Medical Biotechnology

Cell-free DNA (cfDNA) is present in numerous body fluids in addition to initiates generally from blood cells. It is undoubtedly the utmost promising tool among all components of liquid biopsy. Liquid biopsy is a specialized method investigating the nonsolid biological tissue by revealing of circulating cells, cell free DNA etc. that enter body fluids. Since, cancer cells disengage from compact tumors circulate in peripheral blood, evaluating blood of cancer patients holds the opportunities for capture and molecular level analysis of various tumor-derived constituents. Cell free DNA samples can deliver a significant perceptions into oncology, for instance tumor heterogeneity, instantaneous tumor development, response to therapy and treatment, comprising immunotherapy and mechanisms of cancer metastasis. Malignant growth at any phase can outhouse tumor cells in addition to fragments of neoplasticity causing DNA into circulatory system giving noble sign of mutation in the tumor at sampling time. Liquid biopsy distinguishes diverse blood based evolving biomarkers comprising circulating tumor cells (CTCs), circulating tumor DNA (ctDNA) or cfDNA, circulating RNA (cfRNA) and exosomes. Cell free DNA are little DNA fragments found circulating in plasma or serum, just as other fluids present in our body. Cell free DNA involves primarily double stranded nuclear DNA and mitochondrial DNA, present both on a surface level and in the lumen of vesicles. The probable origins of the tumor-inferred portion of cfDNA are apoptosis or tumor necrosis, lysis of CTCs or release of DNA from the tumor cells into circulation. The evolution of innovations, refinement and improvement in therapeutics for determination of cfDNA fragment size and its distribution provide significant information related with pathological conditions of the cell, thus emerging as promising indicator for clinical output in medical biotechnology.

Potential of RASSF1A promoter methylation as a biomarker for colorectal cancer: Meta-analysis and TCGA analysis

The RAS association domain family protein 1A (RASSF1A) is a tumor suppressor in colorectal cancer (CRC), and is often inactived by hypermethylation. Therefore, we evaluated the association between RASSF1A hypermethylation and the risk and prognosis in CRC. We identified literature through searching PubMed and China National Knowledge Infrastructure databases, and then validated and supplemented the meta-analysis with TCGA analysis. Twenty-three studies involving 2886 subjects of CRC were examined. The meta-analysis showed that RASSF1A promoter methylation inferred high CRC risk (odds ratio, 6.53, 95% confidence interval 3.88-11.01, P < .001) and poor overall survival (hazard ratio 2.85, 95% CI 1.88-4.31, P < .001). The TCGA analysis suggested that effect of RASSF1A promotor methylation was affected by tumor localization (colon vs. rectum). RASSF1A promoter methylation was a predictor of high risk (OR 2.38, 95%CI 1.02-5.6, P = .046) and poor disease free survival(HR 2.25, 95%CI 1.27-3.99, P = .006)in colon adenocarcinoma, but the association was statistically insignificant in rectum adenocarcinoma(HR 1.58, 95% CI 0.69-3.59, P = .28). These results suggested RASSF1A hypermethylation is a risk and a potential prognostic biomarker in CRC.

Diagnostic performance of various liquid biopsy methods in detecting colorectal cancer: A meta-analysis

Liquid biopsy is a promising method in detecting colorectal cancer (CRC). However, previous meta‐analyses only focused on the diagnostic performance of cell‐free DNA (cfDNA). Therefore, we firstly evaluated the overall performance of all liquid biopsy methods. The pooled sensitivities, specificities, diagnostic odds ratios, and area under curve (AUC) of summary receiver operating characteristic curve for all liquid biopsy methods, exosomes, circulating tumor cells (CTCs), and cfDNA were calculated, respectively. A total of 62 articles involving 18 739 individuals were included. Fifty‐one articles were about cfDNA, five articles were about CTCs, and six articles were about exosomes. The overall performance of all liquid biopsy methods had a pooled sensitivity, specificity, and AUC of 0.77 (95% confidence interval [CI] 0.76‐0.78), 0.89 (95% CI 0.88‐0.90), and 0.9004, respectively. The sensitivities were 0.82 (95% CI 0.79‐0.85), 0.76 (95% CI 0.72‐0.80), and 0.76 (95% CI 0.75‐0.77) for CTCs, exosomes, and cfDNA, respectively. The specificities were 0.97 (95% CI95% CI 0.95‐0.99), 0.92 (95% CI 0.89‐0.94), and 0.88 (95% CI 0.87‐0.89) for CTCs, exosomes, and cfDNA, respectively. The AUC were 0.9772, 0.9037, and 0.8963 for CTCs, exosomes, and cfDNA, respectively. The overall performance of all liquid biopsy methods had great diagnostic value in detecting CRC, regardless of subtypes. Among all liquid biopsy methods, CTCs showed the best diagnostic performance.

Application of Multiplex Bisulfite PCR-Ligase Detection Reaction-Real-Time Quantitative PCR Assay in Interrogating Bioinformatically Identified, Blood-Based Methylation Markers for Colorectal Cancer

The analysis of CpG methylation in circulating tumor DNA fragments has emerged as a promising approach for the noninvasive early detection of solid tumors, including colorectal cancer (CRC). The most commonly employed assay involves bisulfite conversion of circulating tumor DNA, followed by targeted PCR, then real-time quantitative PCR (alias methylation-specific PCR). This report demonstrates the ability of a multiplex bisulfite PCR-ligase detection reaction-real-time quantitative PCR assay to detect seven methylated CpG markers (CRC or colon specific), in both simulated (approximately 30 copies of fragmented CRC cell line DNA mixed with approximately 3000 copies of fragmented peripheral blood DNA) and CRC patient-derived cell-free DNAs. This scalable assay is designed for multiplexing and incorporates steps for improved sensitivity and specificity, including the enrichment of methylated CpG fragments, ligase detection reaction, the incorporation of ribose bases in primers, and use of uracil DNA glycosylase. Six of the seven CpG markers (located in promoter regions of PPP1R16B, KCNA3, CLIP4, GDF6, SEPT9, and GSG1L) were identified through integrated analyses of genome-wide methylation data sets for 31 different types of cancer. These markers were mapped to CpG sites at the promoter region of VIM; VIM and SEPT9 are established epigenetic markers of CRC. Additional bioinformatics analyses show that the methylation at these CpG sites negatively correlates with the transcription of their corresponding genes.

DNA Methylation-Based Testing in Liquid Biopsies as Detection and Prognostic Biomarkers for the Four Major Cancer Types

Lung, breast, colorectal, and prostate cancers are the most incident worldwide. Optimal population-based cancer screening methods remain an unmet need, since cancer detection at early stages increases the prospects of successful and curative treatment, leading to a lower incidence of recurrences. Moreover, the current parameters for cancer patients' stratification have been associated with divergent outcomes. Therefore, new biomarkers that could aid in cancer detection and prognosis, preferably detected by minimally invasive methods are of major importance. Aberrant DNA methylation is an early event in cancer development and may be detected in circulating cell-free DNA (ccfDNA), constituting a valuable cancer biomarker. Furthermore, DNA methylation is a stable alteration that can be easily and rapidly quantified by methylation-specific PCR methods. Thus, the main goal of this review is to provide an overview of the most important studies that report methylation biomarkers for the detection and prognosis of the four major cancers after a critical analysis of the available literature. DNA methylation-based biomarkers show promise for cancer detection and management, with some studies describing a "PanCancer" detection approach for the simultaneous detection of several cancer types. Nonetheless, DNA methylation biomarkers still lack large-scale validation, precluding implementation in clinical practice.

Epigenetics of colorectal cancer: biomarker and therapeutic potential

Colorectal cancer (CRC), a leading cause of cancer-related death worldwide, evolves as a result of the stepwise accumulation of a series of genetic and epigenetic alterations in the normal colonic epithelium, leading to the development of colorectal adenomas and invasive adenocarcinomas. Although genetic alterations have a major role in a subset of CRCs, the pathophysiological contribution of epigenetic aberrations in this malignancy has attracted considerable attention. Data from the past couple of decades has unequivocally illustrated that epigenetic marks are important molecular hallmarks of cancer, as they occur very early in disease pathogenesis, involve virtually all key cancer-associated pathways and, most importantly, can be exploited as clinically relevant disease biomarkers for diagnosis, prognostication and prediction of treatment response. In this Review, we summarize the current knowledge on the best-studied epigenetic modifications in CRC, including DNA methylation and histone modifications, as well as the role of non-coding RNAs as epigenetic regulators. We focus on the emerging potential for the bench-to-bedside translation of some of these epigenetic alterations into clinical practice and discuss the burgeoning evidence supporting the potential of emerging epigenetic therapies in CRC as we usher in the era of precision medicine.

Developing more sensitive genomic approaches to detect radioresponse in precision radiation oncology: From tissue DNA analysis to circulating tumor DNA

Despite the common application and considerable efforts to achieve precision radiotherapy (RT) in several types of cancer, RT has not yet entered the era of precision medicine; the ability to predict radiosensitivity and treatment responses in tumors and normal tissues is lacking. Therefore, development of genome-based methods for individual prognosis in radiation oncology is urgently required. Traditional DNA sequencing requires tissue samples collected during invasive operations; therefore, repeated tests are nearly impossible. Intra- and inter-tumoral heterogeneity may undermine the predictive power of a single assay from tumor samples. In contrast, analysis of circulating tumor DNA (ctDNA) allows for non-invasive and near real-time sampling of tumors. By investigating the genetic composition of tumors and monitoring dynamic changes during treatment, ctDNA analysis may potentially be clinically valuable in prediction of treatment responses prior to RT, surveillance of responses during RT, and evaluation of residual disease following RT. As a biomarker for RT response, ctDNA profiling may guide personalized treatments. In this review, we will discuss approaches of tissue DNA sequencing and ctDNA detection and summarize their clinical applications in both traditional RT and in combination with immunotherapy.

Early detection of the major male cancer types in blood-based liquid biopsies using a DNA methylation panel

BACKGROUND

Lung (LC), prostate (PCa) and colorectal (CRC) cancers are the most incident in males worldwide. Despite recent advances, optimal population-based cancer screening methods remain an unmet need. Due to its early onset, cancer specificity and accessibility in body fluids, aberrant DNA promoter methylation might be a valuable minimally invasive tool for early cancer detection. Herein, we aimed to develop a minimally invasive methylation-based test for simultaneous early detection of LC, PCa and CRC in males, using liquid biopsies.

RESULTS

Circulating cell-free DNA was extracted from 102 LC, 121 PCa and 100 CRC patients and 136 asymptomatic donors' plasma samples. Sodium-bisulfite modification and whole-genome amplification was performed. Promoter methylation levels of APC_me, FOXA1_me, GSTP1_me, HOXD3_me, RARβ2_me, RASSF1A_me, SEPT9_me and SOX17_me were assessed by multiplex quantitative methylation-specific PCR. SEPT9_me and SOX17_me were the only biomarkers shared by all three cancer types, although they detected CRC with limited sensitivity. A "PanCancer" panel (FOXA1_me, RARβ2_me and RASSF1A_me) detected LC and PCa with 64% sensitivity and 70% specificity, complemented with "CancerType" panel (GSTP1_me and SOX17_me) which discriminated between LC and PCa with 93% specificity, but with modest sensitivity. Moreover, a HOXD3_me and RASSF1A_me panel discriminated small cell lung carcinoma from non-small cell lung carcinoma with 75% sensitivity, 88% specificity, 6.5 LR+ and 0.28 LR-. An APC_me and RASSF1A_me panel independently predicted disease-specific mortality in LC patients.

CONCLUSIONS

We concluded that a DNA methylation-based test in liquid biopsies might enable minimally invasive screening of LC and PCa, improving patient compliance and reducing healthcare costs. Moreover, it might assist in LC subtyping and prognostication.

Evolving Clinical Utility of Liquid Biopsy in Gastrointestinal Cancers

Room for improvement exists regarding recommendations for screening, staging, therapy selection, and frequency of surveillance of gastrointestinal cancers. Screening is costly and invasive, improved staging demands increased sensitivity and specificity to better guide therapy selection. Surveillance requires increased sensitivity for earlier detection and precise management of recurrences. Peripherally collected blood-based liquid biopsies enrich and analyze circulating tumor cells and/or somatic genomic material, including circulating tumor DNA along with various subclasses of RNA. Such assays have the potential to impact clinical practice at multiple stages of management in gastrointestinal cancers. This review summarizes current basic and clinical evidence for the utilization of liquid biopsy in cancers of the esophagus, pancreas, stomach, colon, and rectum. Technical aspects of various liquid biopsy methodologies and targets are reviewed and evidence supporting current commercially available assays is examined. Finally, current clinical applicability, potential future uses, and pitfalls of applying liquid biopsy to the screening, staging and therapeutic management of these diseases are discussed.

Potassium bisperoxo (1,10-phenanthroline) oxovanadate suppresses proliferation of hippocampal neuronal cell lines by increasing DNA methyltransferases

Bisperoxo (1,10-phenanthroline) oxovanadate (BpV) can reportedly block the cell cycle. The present study examined whether BpV alters gene expression by affecting DNA methyltransferases (DNMTs), which would impact the cell cycle. Immortalized mouse hippocampal neuronal precursor cells (HT22) were treated with 0.3 or 3 μM BpV. Proliferation, morphology, and viability of HT22 cells were detected with an IncuCyte real-time video imaging system or inverted microscope and 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethonyphenol)-2-(4-sulfophenyl)-2H-tetrazolium, respectively. mRNA and protein expression of DNMTs and p21 in HT22 cells was detected by real-time polymerase chain reaction and immunoblotting, respectively. In addition, DNMT activity was measured with an enzyme-linked immunosorbent assay. Effects of BpV on the cell cycle were analyzed using flow cytometry. Results demonstrated that treatment with 0.3 μM BpV did not affect cell proliferation, morphology, or viability; however, treatment with 3 μM BpV decreased cell viability, increased expression of both DNMT3B mRNA and protein, and inhibited the proliferation of HT22 cells; and 3 μM BpV also blocked the cell cycle and increased expression of the regulatory factor p21 by increasing DNMT expression in mouse hippocampal neurons.

Interrelations of Apoptotic and Cellular Senescence Genes Methylation in Inflammatory Bowel Disease Subtypes and Colorectal Carcinoma in Egyptians Patients

Ras-related domain family member 1 transcript variant A (RASSF1A) controls apoptosis and cell proliferation while p14/ARF gene has a regulatory role in cellular senescence. Failure of apoptosis and cellular senescence occurs during inflammatory bowel disease (IBD) and colorectal cancer (CRC). To reveal the role of peripheral leukocyte promoter methylation of RASSF1A and p14/ARF in the pathogenesis of IBD subtypes and CRC we investigated the methylation state of the two genes by methylation-specific polymerase chain reaction (MSP-PCR) in 60 CRC patients, 60 patients with IBD; 27 with ulcerative colitis and 33 had Crohn's disease and also in 30 healthy subjects. Methylated RASSF1A and p14/ARF genes were detected in 55% and 60% of CRC, while the frequency of the methylated RASSF1A and p14/ARF genes was 23.3% and 43.3% in IBD patients and 3.3% and 13.3% in the control group (P = 0.000 each). Also, the frequency of methylated RASSF1A gene was significantly higher in ulcerative colitis than in Crohn's disease, while a non-significant frequency of methylated p14/ARF was detected between ulcerative colitis and Crohn's disease. Furthermore, methylated RASSF1A and p14/ARF were associated with the grade of CRC but not associated with the age of patients, family history, or tumor location. Results suggest that methylated RASSF1A and p14/ARF are related to CRC and IBD pathogenesis and may be used as molecular biomarkers for early detection of CRC and IBD.

Epigenetic Characterization of Cell-Free DNA

Cell-free DNA can be evaluated for the epigenetic component. Epigenetic alterations consist of changes in gene functions that do not involve changes in DNA sequence. The mainly studied epigenetic alteration is DNA methylation occurring at CpG islands in the promoter regions for which several literature data showed clinical relevance. This chapter is an overview of the epigenetic alterations detected in cell-free DNA.

Towards DNA methylation detection using biosensors

DNA methylation, a stable and heritable covalent modification which mostly occurs in the context of a CpG dinucleotide, has great potential as a biomarker to detect disease, provide prognoses and predict therapeutic responses. It can be detected in a quantitative manner by many different approaches both genome-wide and at specific gene loci, in various biological fluids such as urine, plasma, and serum, which can be obtained without invasive procedures. The current, classical methods are effective in studying DNA methylation patterns, however, for the most part; they have major drawbacks such as expensive instruments, complicated and time consuming protocols as well as relatively low sensitivity, and high false positive rates. To overcome these obstacles, great efforts have been made toward the development of reliable sensor devices to solve these limitations, providing sensitive, fast and cost-effective measurements. The use of biosensors for DNA methylation biomarkers has increased in recent years, because they are portable, simple, rapid, and inexpensive which offers a straightforward way to detect methylated biomarkers. In this review, we give an overview of the conventional techniques for the detection of DNA methylation and then will focus on recent advances in biosensor based methylation detection that eliminate bisulfite conversion and PCR amplification.

The liquid biopsy in the management of colorectal cancer patients: Current applications and future scenarios

The term liquid biopsy refers to the analysis of biomarkers in any body fluid, including blood, urine and cerebrospinal fluid. In cancer, liquid biopsy testing allows the analysis of tumor-derived DNA, RNA, miRNA and proteins that can be either cell-free or contained in circulating tumor cells (CTC), extracellular vesicles (EVs) or platelets. A number of studies suggest that liquid biopsy testing could have a relevant role in the management of colorectal cancer (CRC) patients at different stages of the disease. Analysis of cell-free DNA (cfDNA), CTC and/or miRNA can provide relevant information for the early diagnosis of CRC and the identification of minimal residual disease and, more generally, the evaluation of the risk of recurrence in early CRC patients. In addition, liquid biopsy testing might allow the assessment of prognostic and predictive biomarkers in metastatic CRC patients, and the monitoring of the response to treatment and of the clonal evolution of the disease. While a number of elegant studies have shown the potential of liquid biopsy in CRC, the possibility to use this approach in the daily clinical practice is still limited. The use of non-standardized methods, the small cohorts of patients analyzed, the lack of demonstration of a clear clinical benefit are the main limitations of the studies with liquid biopsy in CRC reported up to now. The potential of this approach and the steps that need still to be taken to translate these preliminary findings in the clinic are discussed in this review.

Blood-based DNA Methylation Biomarkers for Early Detection of Colorectal Cancer

Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide. Early detection of CRC can significantly reduce this mortality rate. Unfortunately, recommended screening modalities, including colonoscopy, are hampered by poor patient acceptance, low sensitivity and high cost. Recent studies have demonstrated that colorectal oncogenesis is a multistep event resulting from the accumulation of a variety of genetic and epigenetic changes in colon epithelial cells, which can be reflected by epigenetic alterations in blood. DNA methylation is the most extensively studied dysregulated epigenetic mechanism in CRC. In this review, we focus on current knowledge on DNA methylation as potential blood-based biomarkers for early detection of CRC.

Deregulation of methylation of transcribed-ultra conserved regions in colorectal cancer and their value for detection of adenomas and adenocarcinomas

Expression of Transcribed Ultraconserved Regions (T-UCRs) is often deregulated in cancer. The present study assesses the expression and methylation of three T-UCRs (Uc160, Uc283 and Uc346) in colorectal cancer (CRC) and explores the potential of T-UCR methylation in circulating DNA for the detection of adenomas and adenocarcinomas.

Expression levels of Uc160, Uc283 and Uc346 were lower in neoplastic tissues from 64 CRC patients (statistically significant for Uc160, p<0.001), compared to non-malignant tissues, while methylation levels displayed the inverse pattern (p<0.001, p=0.001 and p=0.004 respectively). In colon cancer cell lines, overexpression of Uc160 and Uc346 led to increased proliferation and migration rates. Methylation levels of Uc160 in plasma of 50 CRC, 59 adenoma patients, 40 healthy subjects and 12 patients with colon inflammation or diverticulosis predicted the presence of CRC with 35% sensitivity and 89% specificity (p=0.016), while methylation levels of the combination of all three T-UCRs resulted in 45% sensitivity and 74.3% specificity (p=0.013). In conclusion, studied T-UCRs’ expression and methylation status are deregulated in CRC while Uc160 and Uc346 appear to have a complicated role in CRC progression. Moreover their methylation status appears a promising non-invasive screening test for CRC, provided that the sensitivity of the assay is improved.

Epigenomic biomarkers for prognostication and diagnosis of gastrointestinal cancers

Altered epigenetic regulation is central to many human diseases, including cancer. Over the past two decade, major advances have been made in our understanding of the role of epigenetic alterations in carcinogenesis, particularly for DNA methylation, histone modifications and non-coding RNAs. Aberrant hypermethylation of DNA at CpG islands is a well-established phenomenon that mediates transcriptional silencing of tumor suppressor genes, and it is an early event integral to gastrointestinal cancer development. As such, detection of aberrant DNA methylation is being developed as biomarkers for prognostic and diagnostic purposes in gastrointestinal cancers. Diverse tissue types are suitable for the analyses of methylated DNA, such as tumor tissues, blood, plasma, and stool, and some of these markers are already utilized in the clinical setting. Recent advances in the genome-wide epigenomic approaches are enabling the comprehensive mapping of the cancer methylome, thus providing new avenues for mining novel biomarkers for disease prognosis and diagnosis. Here, we review the current knowledge on DNA methylation biomarkers for the prognostication and non-invasive diagnosis of gastrointestinal cancers and highlight their clinical application.

The prognostic efficacy of cell-free DNA hypermethylation in colorectal cancer

Epigenetic alterations in colorectal cancer (CRC) cause important differences in the underlying tumor biology and aggressiveness. DNA hypermethylation is central for the development of CRC but the prognostic impact remains elusive. We aimed to assess the association between cell-free hypermethylated DNA and stage and survival in colorectal cancer (CRC). We analyzed pre-treatment plasma samples from 193 patients with CRC. Thirty gene-promoter regions were analyzed using methylation specific PCR. We compared the median number (range) of hypermethylated promoter regions with CRC stage, and constructed a multivariable Cox-regression model adjusted for stage, to evaluate the added prognostic information. The median number of hypermethylated promoter regions was nine (0-28) in patients with distant metastasis compared to five (0-19) in patients without metastatic disease (p < 0.0001). The majority of the hypermethylated promoter regions inferred a poor prognosis. Cox-regression analysis adjusted for patient age, sex, pre-treatment CEA-levels, and disease stage, showed that RARB (HR = 1.99, 95% CI [1.07, 3.72]) and RASSF1A (HR = 3.35, 95% CI [1.76, 6.38]) hypermethylation inferred a significant effect on survival. The risk of metastasis increase with the number of cell-free hypermethylated promoter regions. The presence of RARB and RASSF1A hypermethylation indicated aggressive disease, regardless of stage at the time of diagnosis.

Hypermethylated in cancer 1(HIC1) suppresses non-small cell lung cancer progression by targeting interleukin-6/Stat3 pathway

Non-small cell lung cancer (NSCLC), which accounts for more than 80% of lung cancers, is a leading cause of cancer mortality worldwide. However, the mechanism underlying its progression remains unclear. Here we found that HIC1 promoter was heavily methylated in NSCLC cell lines and tissues contributing to its low expression compared to normal controls. Restoring HIC1 expression inhibited migration, invasion and promoted inducible apoptosis of NSCLC cells. Notably, HIC1 is a tumor suppressor through inhibiting the transcription of IL-6 by sequence-specific binding on its promoter. Restoring IL-6 expression could partially rescue these phenotypes induced by HIC1 in vitro and in vivo. Mechanistic analyses show that autocrine secretion of IL-6 induced by loss of HIC1 activated STAT3 through IL-6/JAK pathway and was associated with NSCLC progression. The HIC1/IL-6 axis may serve as a prognostic biomarker and provide an attractive therapeutic target for NSCLC.

The evidence base for circulating tumour DNA blood-based biomarkers for the early detection of cancer: a systematic mapping review

BACKGROUND

The presence of circulating cell-free DNA from tumours in blood (ctDNA) is of major importance to those interested in early cancer detection, as well as to those wishing to monitor tumour progression or diagnose the presence of activating mutations to guide treatment. In 2014, the UK Early Cancer Detection Consortium undertook a systematic mapping review of the literature to identify blood-based biomarkers with potential for the development of a non-invasive blood test for cancer screening, and which identified this as a major area of interest. This review builds on the mapping review to expand the ctDNA dataset to examine the best options for the detection of multiple cancer types.

METHODS

The original mapping review was based on comprehensive searches of the electronic databases Medline, Embase, CINAHL, the Cochrane library, and Biosis to obtain relevant literature on blood-based biomarkers for cancer detection in humans (PROSPERO no. CRD42014010827). The abstracts for each paper were reviewed to determine whether validation data were reported, and then examined in full. Publications concentrating on monitoring of disease burden or mutations were excluded.

RESULTS

The search identified 94 ctDNA studies meeting the criteria for review. All but 5 studies examined one cancer type, with breast, colorectal and lung cancers representing 60% of studies. The size and design of the studies varied widely. Controls were included in 77% of publications. The largest study included 640 patients, but the median study size was 65 cases and 35 controls, and the bulk of studies (71%) included less than 100 patients. Studies either estimated cfDNA levels non-specifically or tested for cancer-specific mutations or methylation changes (the majority using PCR-based methods).

CONCLUSION

We have systematically reviewed ctDNA blood biomarkers for the early detection of cancer. Pre-analytical, analytical, and post-analytical considerations were identified which need to be addressed before such biomarkers enter clinical practice. The value of small studies with no comparison between methods, or even the inclusion of controls is highly questionable, and larger validation studies will be required before such methods can be considered for early cancer detection.

Promoter methylation of tumor-related genes as a potential biomarker using blood samples for gastric cancer detection

Gene promoter methylation has been reported in gastric cancer (GC). However, the potential applications of blood-based gene promoter methylation as a noninvasive biomarker for GC detection remain to be evaluated. Hence, we performed this analysis to determine whether promoter methylation of 11 tumor-related genes could become a promising biomarker in blood samples in GC. We found that the cyclin-dependent kinase inhibitor 2A (p16), E-cadherin (CDH1), runt-related transcription factor 3 (RUNX3), human mutL homolog 1 (MLH1), RAS association domain family protein 1A (RASSF1A), cyclin-dependent kinase inhibitor 2B (p15), adenomatous polyposis coli (APC), Glutathione S-transferase P1 (GSTP1), TP53 dependent G2 arrest mediator candidate (Reprimo), and O6-methylguanine-DNAmethyl-transferase (MGMT) promoter methylation was notably higher in blood samples of patients with GC compared with non-tumor controls. While death-associated protein kinase (DAPK) promoter methylation was not correlated with GC. Further analyses demonstrated that RUNX3, RASSF1A and Reprimo promoter methylation had a good diagnostic capacity in blood samples of GC versus non-tumor controls (RUNX3: sensitivity = 63.2% and specificity = 97.5%, RASSF1A: sensitivity = 61.5% and specificity = 96.3%, Reprimo: sensitivity = 82.0% and specificity = 89.0%). Our findings indicate that promoter methylation of the RUNX3, RASSF1A and Reprimo genes could be powerful and potential noninvasive biomarkers for the detection and diagnosis of GC in blood samples in clinical practices, especially Reprimo gene. Further well-designed (multi-center) and prospective clinical studies with large populations are needed to confirm these findings in the future.

Future perspectives of circulating tumor DNA in colorectal cancer

Tumor biopsy is currently the gold standard for diagnosis and in determining cell signaling pathways involved in the development of treatment resistance. However, there are major challenges with this technique, including the need for serial sampling to monitor treatment resistance, which is invasive and also has the potential for selection bias due to intra-tumoral and inter-tumoral heterogeneity. These challenges highlight the need for more effective methods for obtaining Tumor samples. Liquid biopsy analyzes genetic material or tumor cells shed into the blood from the primary tumor and metastatic sites and consequently provides a comprehensive, real-time picture of the tumor burden in an individual patient. Indeed, liquid biopsy has the potential to revolutionize cancer management. Here, we review recent studies on the potential clinical applications of liquid biopsy using circulating tumor DNA in colorectal cancer, including screening, diagnosis, detection of minimal residual disease after surgery, detection of recurrence, prognosis, predicting treatment response, monitoring tumor burden or response during treatment, and tracking resistance. We also discuss recent data demonstrating the utility of detecting KRAS-mutated circulating tumor DNA, both at diagnosis to determine an appropriate treatment strategy and during anti-epidermal growth factor receptor therapy to predict treatment resistance. The future integration of liquid biopsy into clinical practice is discussed, together with alternative approaches and key questions that need to be answered in future clinical studies before this technology can be implemented and used routinely.

Abnormal DNA methylation as a cell-free circulating DNA biomarker for colorectal cancer detection: A review of literature

Colorectal cancer (CRC) is one of the most prevalent malignancies in the world. CRC-associated morbidity and mortality is continuously increasing, in part due to a lack of early detection. The existing screening tools such as colonoscopy, are invasive and yet high cost, affecting the willingness of patients to participate in screening programs. In recent years, evidence is accumulating that the interaction of aberrant genetic and epigenetic modifications is the cornerstone for the CRC development and progression by alternating the function of tumor suppressor genes, DNA repair genes and oncogenes of colonic cells. Apart from the understanding of the underlying mechanism(s) of carcinogenesis, the aforementioned interaction has also allowed identification of clinical biomarkers, especially epigenetic, for the early detection and prognosis of cancer patients. One of the ways to detect these epigenetic biomarkers is the cell-free circulating DNA (circDNA), a blood-based cancer diagnostic test, mainly focusing in the molecular alterations found in tumor cells, such as DNA mutations and DNA methylation. In this brief review, we epitomize the current knowledge on the research in circDNA biomarkers - mainly focusing on DNA methylation - as potential blood-based tests for early detection of colorectal cancer and the challenges for validation and globally implementation of this emergent technology.

MALDI imaging mass spectrometry reveals multiple clinically relevant masses in colorectal cancer using large-scale tissue microarrays

For identification of clinically relevant masses to predict status, grade, relapse and prognosis of colorectal cancer, we applied Matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS) to a tissue micro array containing formalin-fixed and paraffin-embedded tissue samples from 349 patients. Analysis of our MALDI-IMS data revealed 27 different m/z signals associated with epithelial structures. Comparison of these signals showed significant association with status, grade and Ki-67 labeling index. Fifteen out of 27 IMS signals revealed a significant association with survival. For seven signals (m/z 654, 776, 788, 904, 944, 975 and 1013) the absence and for eight signals (m/z 643, 678, 836, 886, 898, 1095, 1459 and 1477) the presence were associated with decreased life expectancy, including five masses (m/z 788, 836, 904, 944 and 1013) that provided prognostic information independently from the established prognosticators pT and pN. Combination of these five masses resulted in a three-step classifier that provided prognostic information superior to univariate analysis. In addition, a total of 19 masses were associated with tumor stage, grade, metastasis and cell proliferation. Our data demonstrate the suitability of combining IMS and large-scale tissue micro arrays to simultaneously identify and validate clinically useful molecular marker. Copyright © 2017 John Wiley & Sons, Ltd.

Case-control study of candidate gene methylation and adenomatous polyp formation

PURPOSE

Colorectal cancer (CRC) is one of the most common and preventable forms of cancer but remains the second leading cause of cancer-related death. Colorectal adenomas are precursor lesions that develop in 70-90 % of CRC cases. Identification of peripheral biomarkers for adenomas would help to enhance screening efforts. This exploratory study examined the methylation status of 20 candidate markers in peripheral blood leukocytes and their association with adenoma formation.

METHODS

Patients recruited from a local endoscopy clinic provided informed consent and completed an interview to ascertain demographic, lifestyle, and adenoma risk factors. Cases were individuals with a histopathologically confirmed adenoma, and controls included patients with a normal colonoscopy or those with histopathological findings not requiring heightened surveillance (normal biopsy, hyperplastic polyp). Methylation-specific polymerase chain reaction was used to characterize candidate gene promoter methylation. Odds ratios (ORs) and 95 % confidence intervals (95% CIs) were calculated using unconditional multivariable logistic regression to test the hypothesis that candidate gene methylation differed between cases and controls, after adjustment for confounders.

RESULTS

Complete data were available for 107 participants; 36 % had adenomas (men 40 %, women 31 %). Hypomethylation of the MINT1 locus (OR 5.3, 95% CI 1.0-28.2) and the PER1 (OR 2.9, 95% CI 1.1-7.7) and PER3 (OR 11.6, 95% CI 1.6-78.5) clock gene promoters was more common among adenoma cases. While specificity was moderate to high for the three markers (71-97 %), sensitivity was relatively low (18-45 %).

CONCLUSION

Follow-up of these epigenetic markers is suggested to further evaluate their utility for adenoma screening or surveillance.

Cell-free DNA as a diagnostic marker for cancer: current insights

The increasing knowledge of the molecular pathogenesis of cancer and the rapid development of new molecular techniques are promoting the study of early molecular alterations involved in cancer development in body fluids. Specific genetic and epigenetic alterations could be found in plasma, serum, and urine cell-free DNA (cfDNA) and could potentially be used as diagnostic biomarkers for several types of cancers. This review focuses on the role of cfDNA in diagnosis: a PubMed search was performed by selecting papers according to journal impact factor and robustness of statistical analysis. A comprehensive evaluation of “liquid biopsy”, including cfDNA analysis, will be one of the critical challenges to better understand the early mechanisms of cancer development.

Role of Urinary Biomarkers in the Diagnosis of Adenoma and Colorectal Cancer: A Systematic Review and Meta-Analysis

The growing interest in enhancing and spreading colorectal cancer (CRC) screening has been stimulating the exploration of novel biomarkers with greater sensitivity and specificity than immunochemical faecal occult blood test (iFOBT). The present study provides i) a systematic review of the urinary biomarkers that have been tested to achieve early CRC diagnosis and assess the risk of colorectal adenoma and adenocarcinoma, and ii) a meta-analysis of the data regarding the urinary prostaglandin (PG) metabolite PGE-M. As regard to gene markers, we found significantly different percent methylation of the vimentin gene in CRC patients and healthy controls (HC) (p<0.0001). Respect to metabolism of nitrogenous bases, cytidine, 1-methyladenosine, and adenosine, have higher concentrations in CRC patients than in HC (respectively, p<0.01, p=0.01, and p<0.01). As regard to spermine we found that N1,N12 diacetyl spermine (DiAcSpm) and N1, N8 diacetylspermidine (DiAcSpd) were significantly higher in CRC than in HC (respectively p=0.01 and p<0.01). Respect to PGE-M, levels were higher in CRC than in those with multiple polyposis (p<0.006) and HC subjects (p<0.0004). PGE-M seems to be the most interesting and promising urinary marker for CRC and adenoma risk assessment and for CRC screening. In conclusion, evidence suggests that urinary biomarker could have a potential role as urinary biomarkers in the diagnosis of colorectal cancer. Particularly, PGE-M seems to be the most promising urinary marker for CRC early detection.

DNA methylation based biomarkers in colorectal cancer: A systematic review

Since genetic and epigenetic alterations influence the development of colorectal cancer (CRC), huge potential lies in the use of DNA methylation as biomarkers to improve the current diagnosis, screening, prognosis and treatment prediction. Here we performed a systematic review on DNA methylation-based biomarkers published in CRC, and discussed the current state of findings and future challenges. Based on the findings, we then provide a perspective on future studies. Genome-wide studies on DNA methylation revealed novel biomarkers as well as distinct subgroups that exist in CRC. For diagnostic purposes, the most independently validated genes to study further are VIM, SEPT9, ITGA4, OSM4, GATA4 and NDRG4. These hypermethylated biomarkers can even be combined with LINE1 hypomethylation and the performance of markers should be examined in comparison to FIT further to find sensitive combinations. In terms of prognostic markers, myopodin, KISS1, TMEFF2, HLTF, hMLH1, APAF1, BCL2 and p53 are independently validated. Most prognostic markers published lack both a multivariate analysis in comparison to clinical risk factors and the appropriate patient group who will benefit by adjuvant chemotherapy. Methylation of IGFBP3, mir148a and PTEN are found to be predictive markers for 5-FU and EGFR therapy respectively. For therapy prediction, more studies should focus on finding markers for chemotherapeutic drugs as majority of the patients would benefit. Translation of these biomarkers into clinical utility would require large-scale prospective cohorts and randomized clinical trials in future. Based on these findings and consideration we propose an avenue to introduce methylation markers into clinical practice in near future. For future studies, multi-omics profiling on matched tissue and non-invasive cohorts along with matched cohorts of adenoma to carcinoma is indispensable to concurrently stratify CRC and find novel, robust biomarkers. Moreover, future studies should examine the timing and heterogeneity of methylation as well as the difference in methylation levels between epithelial and stromal tissues.

Hypermethylated DNA as a biomarker for colorectal cancer: a systematic review

AIM

Improved methods for early detection of colorectal cancer (CRC) are essential for increasing survival. Hypermethylated DNA in blood or stool has been proposed as a biomarker for CRC. Biochemical methods have improved in recent years, and several hypermethylated genes that are sensitive and specific for CRC have been proposed. Articles describing the use of hypermethylated promoter regions in blood or stool as biomarkers for CRC were systematically reviewed.

METHOD

A systematic literature search was performed using the Medline, Web of Science and Embase databases. Studies were included if they analysed hypermethylated genes from stool or blood samples in correlation with CRC. Studies in languages other than English and those based on animal models or cell lines were excluded.

RESULTS

The literature search yielded 74 articles, including 43 addressing blood samples and 31 addressing stool samples. In blood samples, hypermethylated ALX4, FBN2, HLTF, P16, TMEFF1 and VIM were associated with poor prognosis, hypermethylated APC, NEUROG1, RASSF1A, RASSF2A, SDC2, SEPT9, TAC1 and THBD were detected in early stage CRC and hypermethylated P16 and TFPI2 were associated with CRC recurrence. In stool samples, hypermethylated BMP3, PHACTR3, SFRP2, SPG20, TFPI2 and TMEFF2 were associated with early stage CRC.

CONCLUSION

Hypermethylation of the promoters of specific genes measured in blood or stool samples could be used as a CRC biomarker and provide prognostic information. The majority of studies, however, include only a few patients with poorly defined control groups. Further studies are therefore needed before hypermethylated DNA can be widely applied as a clinical biomarker for CRC detection and prognosis.

Diagnostic Performance of DNA Hypermethylation Markers in Peripheral Blood for the Detection of Colorectal Cancer: A Meta-Analysis and Systematic Review

DNA hypermethylation in blood is becoming an attractive candidate marker for colorectal cancer (CRC) detection. To assess the diagnostic accuracy of blood hypermethylation markers for CRC in different clinical settings, we conducted a meta-analysis of published reports. Of 485 publications obtained in the initial literature search, 39 studies were included in the meta-analysis. Hypermethylation markers in peripheral blood showed a high degree of accuracy for the detection of CRC. The summary sensitivity was 0.62 [95% confidence interval (CI), 0.56-0.67] and specificity was 0.91 (95% CI, 0.89-0.93). Subgroup analysis showed significantly greater sensitivity for the methylated Septin 9 gene (SEPT9) subgroup (0.75; 95% CI, 0.67-0.81) than for the non-methylated SEPT9 subgroup (0.58; 95% CI, 0.52-0.64). Sensitivity and specificity were not affected significantly by target gene number, CRC staging, study region, or methylation analysis method. These findings show that hypermethylation markers in blood are highly sensitive and specific for CRC detection, with methylated SEPT9 being particularly robust. The diagnostic performance of hypermethylation markers, which have varied across different studies, can be improved by marker optimization. Future research should examine variation in diagnostic accuracy according to non-neoplastic factors.

DNA Methylation in Whole Blood: Uses and Challenges

Due to its convenience, the blood is commonly used in epigenomic studies, but its heterogeneous nature leads to interpretation difficulties, given the now widely recognized potential for confounding by cell composition effects. Many recent publications have reported significant associations between DNA methylation and a variety of health conditions or exposures. In this review, we summarize many of these recent publications, highlighting the findings in the context of potential cell composition effects, particularly findings that are indicative of immune response or inflammation. While there is substantial evidence for confounding by cell composition, there is nevertheless also evidence for differential DNA methylation suggestive of processes that are not cell mediated. We conclude that important biological insights still may be gained from studying DNA methylation in whole blood, either by investigating the cell composition effects themselves or processes that demonstrate associations even after adjusting for cell composition effects.

Noninvasive DNA methylation biomarkers in colorectal cancer: A systematic review

OBJECTIVE

To summarize the current evidence on the biomarkers associated with DNA methylation in the screening and diagnosis of colorectal cancer (CRC).

METHODS

A literature search was conducted on the databases of PubMed and Web of Science to identify articles published from 1 January 2000 to 6 June 2015 with language striction. Stuides focusing on the association between noninvasive biomarkers indicating DNA methylation and CRC were included.

RESULTS

Altogether 74 studies were finally included in the study. Varied genetic markers in the feces and blood samples were hypermethylated in patients with CRC than in the healthy controls. Some of them could even be detected at the early stage of the tumors. The sensitivity of the genetic markers was superior to that of fecal occult blood test and carcinoembryonic antigen. Multitarget DNA assays using a combination of different methylated genes could improve the diagnostic sensitivity.

CONCLUSIONS

Genetic markers might be minimally invasive, economical and accurate for the screening and surveillance of CRC. Large multicenter studies evaluating these biomarkers systematically and prospectively not only in CRC but also in other types of cancers are needed in the future.

"Liquid biopsy"-ctDNA detection with great potential and challenges

Circulating tumor DNA (ctDNA) is now being extensively studied as it is a noninvasive "real-time" biomarker that can provide diagnostic and prognostic information before, during treatment and at progression. These include DNA mutations, epigenetic alterations and other forms of tumor-specific abnormalities such as microsatellite instability (MSI) and loss of heterozygosity (LOH). ctDNA is of great value in the process of cancer treatment. However, up to date, there is no strict standard considering the exact biomarker because the development and progression of cancer is extremely complicated. Also, results of the studies evaluating ctDNA are not consistent due to the different detection methods and processing. The major challenge is still assay sensitivity and specificity for analysis of ctDNA. This review mainly focuses on the tumor specific DNA mutations, epigenetic alterations as well as detecting methods of ctDNA. The advantages and disadvantages will also be discussed.

Value of DNA methylation markers in colorectal cancer screening

Colorectal cancer (CRC) is one of the most common malignant tumors in the world. Recognizing CRC at an early stage by population-based screening is crucial in the prevention and treatment of CRC. Numerous candidate genes, which play important roles in the development and progression of CRC, have been found to be hyper-methylated in the promoter regions in recent studies. The promoter fragments of those hyper-methylated genes in tumor tissues have also been detected in the blood and fecal specimens, with higher sensitivity and specificity than traditional markers in the screening of CRC, including carcino-embryonic antigen (CEA) and fecal occult blood test. Here, we will discuss what we have already known about the DNA methylation markers for CRC screening and the potential research direction in the future.

Choosing the optimal method in programmatic colorectal cancer screening: current evidence and controversies

Colorectal cancer (CRC) is an important health problem all over the world, being the third most common cancer and the second leading cause of cancer-related death in Western countries. The most important strategy for CRC prevention is screening (i.e. secondary prevention). Since it is widely accepted that adenomas and serrated polyps are the precursors of the vast majority of CRC, early detection and removal of these lesions is associated with a reduction of CRC incidence and, consequently, mortality. Moreover, cancers detected by screening are usually diagnosed at early stages and, therefore, curable by endoscopic or surgical procedures. This review will be address CRC screening strategies in average-risk population, which is defined by those individuals, men and women, 50 years of age or older, without any additional personal or familial predisposing risk factor. In order to maximize the impact of screening and ensure high coverage and equity of access, only organized screening programs (i.e. programmatic screening) should be implemented, as opposed to case-finding or opportunistic screening. For that reason and considering that the optimal approach for colorectal screening may differ depending on the scenario, this review will be focused on the advantages and limitations of each screening strategy in an organized setting.