A simplified, noninvasive stool DNA test for colorectal cancer detection

Current Research on Molecular Biomarkers for Colorectal Cancer in Stool Samples

Colorectal cancer (CRC) is one of the most diagnosed cancers worldwide, with a high incidence and mortality rate when diagnosed late. Currently, the methods used in healthcare to diagnose CRC are the fecal occult blood test, flexible sigmoidoscopy, and colonoscopy. However, the lack of sensitivity and specificity and low population adherence are driving the need to implement other technologies that can identify biomarkers that not only help with early CRC detection but allow for the selection of more personalized treatment options. In this regard, the implementation of omics technologies, which can screen large pools of biological molecules, coupled with molecular validation, stands out as a promising tool for the discovery of new biomarkers from biopsied tissues or body fluids. This review delves into the current state of the art in the identification of novel CRC biomarkers that can distinguish cancerous tissue, specifically from fecal samples, as this could be the least invasive approach.

Colorectal Cancer: Current Updates and Future Perspectives

Colorectal cancer is a frequent neoplasm in western countries, mainly due to dietary and behavioral factors. Its incidence is growing in developing countries for the westernization of foods and lifestyles. An increased incidence rate is observed in patients under 45 years of age. In recent years, the mortality for CRC is decreased, but this trend is slowing. The mortality rate is reducing in those countries where prevention and treatments have been implemented. The survival is increased to over 65%. This trend reflects earlier detection of CRC through routine clinical examinations and screening, more accurate staging through advances in imaging, improvements in surgical techniques, and advances in chemotherapy and radiation. The most important predictor of survival is the stage at diagnosis. The screening programs are able to reduce incidence and mortality rates of CRC. The aim of this paper is to provide a comprehensive overview of incidence, mortality, and survival rate for CRC.

Current Status and Emerging Trends in Colorectal Cancer Screening and Diagnostics

Colorectal cancer (CRC) is a prevalent and potentially fatal disease categorized based on its high incidences and mortality rates, which raised the need for effective diagnostic strategies for the early detection and management of CRC. While there are several conventional cancer diagnostics available, they have certain limitations that hinder their effectiveness. Significant research efforts are currently being dedicated to elucidating novel methodologies that aim at comprehending the intricate molecular mechanism that underlies CRC. Recently, microfluidic diagnostics have emerged as a pivotal solution, offering non-invasive approaches to real-time monitoring of disease progression and treatment response. Microfluidic devices enable the integration of multiple sample preparation steps into a single platform, which speeds up processing and improves sensitivity. Such advancements in diagnostic technologies hold immense promise for revolutionizing the field of CRC diagnosis and enabling efficient detection and monitoring strategies. This article elucidates several of the latest developments in microfluidic technology for CRC diagnostics. In addition to the advancements in microfluidic technology for CRC diagnostics, the integration of artificial intelligence (AI) holds great promise for further enhancing diagnostic capabilities. Advancements in microfluidic systems and AI-driven approaches can revolutionize colorectal cancer diagnostics, offering accurate, efficient, and personalized strategies to improve patient outcomes and transform cancer management.

Recent advancements in biosensor designs toward the detection of intestine cancer miRNA biomarkers

Cancer diagnosis and treatment have been of broad interest among scientists in the last decades due to the high death rate, widespread occurrence, and recurrence after treatment. The survival rate of cancer patients depends greatly on early detection and appropriate treatments. Therefore developing new technologies applicable to sensitive and specific methods of cancer detection is an inevitable task for cancer researchers. Abnormal miRNA expression is contributed to severe diseases such as cancers and since their expression level and type differ strictly during carcinogenesis and later metastasis and treatments, the improved detection accuracy of these miRNAs would undoubtedly lead to early diagnosis, prognosis, and targeted therapy. Biosensors are accurate and straightforward analytical devices that have had practical applications especially in the last decade. Their domain is still growing through a combination of attractive nanomaterials and amplification methods, leading to innovative biosensing platforms for the efficient detection of miRNAs as diagnostic and prognostic biomarkers. In this review, we will provide the recent developments in biosensors to detect intestine cancer miRNA biomarkers and also discuss the challenges and outcomings of this field.

Aberrant circulating tumor DNA methylation and exosomal microRNA biomarkers for early detection of colorectal cancer

INTRODUCTION

Colorectal cancer (CRC) became the third most commonly diagnosed malignancy and the second leading cause of cancer death in 2020. However, the rates of early screening and early diagnosis for CRC remain unsatisfactory. Thus, it is essential to explore the initiating factors of CRC and strategies for its early diagnosis. Research progress in liquid biopsy has led to the finding that circulating tumor-derived DNA (ctDNA) and exosomes play vital roles in early detection of CRC. THE APPLICATIONS OF LIQUID BIOPSY FOR EARLY DETECTION OF COLORECTAL CANCER: Moreover, the increased understanding of epigenetics has highlighted the role of ctDNA methylation in CRC carcinogenesis, and the detection of aberrant ctDNA methylation markers is a feasible strategy for diagnosis of early-stage CRC. Among exosomal markers, microRNAs (miRNAs) are abundant and are the most researched. Upregulated or downregulated expression of exosome-derived miRNAs can indicate the occurrence of early-stage CRC.

FUTURE PERSPECTIVE

The current research progress on aberrant ctDNA methylation and tumor exosomal miRNA biomarkers in early detection of CRC is summarized in this review, and the advantages and shortcomings of the methods are discussed.

Diagnostic and prognostic biomarkers in colorectal cancer and the potential role of exosomes in drug delivery

Colorectal cancer (CRC) is third most common cancer with second most common cause of death worldwide. One fourth to one fifth of the CRC cases are detected at advance stage. Early detection of colorectal cancer might help in decreasing mortality and morbidity worldwide. CRC being a heterogeneous disease, new non-invasive approaches are needed to complement and improve the screening and management of CRC. Reliable and early detectable biomarkers would improve diagnosis, prognosis, therapeutic responses, and will enable the prediction of drug response and recurrence risk. Over the past decades molecular research has demonstrated the potentials of CTCs, ctDNAs, circulating mRNA, ncRNAs, and exosomes as tumor biomarkers. Non-invasive screening approaches using fecal samples for identification of altered gut microbes in CRC is also gaining attention. Exosomes can be potential candidates that can be employed in the drug delivery system. Further, the integration of in vitro, in vivo and in silico models that involve CRC biomarkers will help to understand the interactions occurring at the cellular level. This review summarizes recent update on CRC biomarkers and their application along with the nanoparticles followed by the application of organoid culture in CRC.

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 Diagnostic Biomarkers in Colorectal Cancer

Colorectal cancer (CRC) is still a leading cause of cancer death worldwide. Less than half of cases are diagnosed when the cancer is locally advanced. CRC is a heterogenous disease associated with a number of genetic or somatic mutations. Diagnostic markers are used for risk stratification and early detection, which might prolong overall survival. Nowadays, the widespread use of semi-invasive endoscopic methods and feacal blood tests characterised by suboptimal accuracy of diagnostic results has led to the detection of cases at later stages. New molecular noninvasive tests based on the detection of CRC alterations seem to be more sensitive and specific then the current methods. Therefore, research aiming at identifying molecular markers, such as DNA, RNA and proteins, would improve survival rates and contribute to the development of personalized medicine. The identification of “ideal” diagnostic biomarkers, having high sensitivity and specificity, being safe, cheap and easy to measure, remains a challenge. The purpose of this review is to discuss recent advances in novel diagnostic biomarkers for tumor tissue, blood and stool samples in CRC patients.

Superiority of fecal carcinoembryonic antigen as diagnosis marker for adenomatous polyposis coli and asymptomatic colorectal cancer

BACKGROUND

Non-invasive diagnostic tools of adenomatous polyposis coli (APC) and asymptomatic colorectal cancer (CRC) are urgently needed. Although fecal carcinoembryonic antigen (FCEA) has been documented in some studies, the diagnostic potential for the detection of APC and asymptomatic CRC has not been described yet.

METHODS

This is a retrospective study. The pre-diagnostic serum carcinoembryonic antigen (SCEA) and fecal occult blood test (FOBT) levels were retrospectively analyzed in 212 patients with intestinal diseases group (IDG) and 224 controls. The levels of FCEA across all the studied groups were measured using electronic chemiluminescence immunoassay (ECLIA), and their sensitivity and specificity were used to evaluate their diagnostic potential. The individual diagnostic accuracy of the three indices, as well as their combined diagnostic potential, was compared using the receiver operating characteristic (ROC) curve and chi-square test.

RESULTS

The FCEA had low sensitivity (50%) and high specificity (93.91%) for the diagnosis of IDG, with the area under the curve (AUC) value of 0.781. The AUC of FCEA was higher than that of SCEA for the diagnosis of APC and CRC in the APC, asymptomatic CRC, and APC + CRC-stage I patients. The AUCs of FCEA were 0.708 and 0.691 for the 'double-negative patients' and 'triple-negative patients', respectively. In addition, FCEA could diagnose 45.5% of the 'double-negative' patients, 43.3% of the asymptomatic patients, and 42.9% of the 'triple-negative' patients. The combination of FCEA and FOBT improved the diagnostic value (AUC = 0.916).

CONCLUSION

FCEA has been demonstrated to be a favorable diagnostic marker in intestinal diseases, especially in the APC, asymptomatic CRC, and 'double-negative' or 'triple-negative' CRC patients.

Step-adjusted tree-based reinforcement learning for evaluating nested dynamic treatment regimes using test-and-treat observational data

Dynamic treatment regimes (DTRs) include a sequence of treatment decision rules, in which treatment is adapted over time in response to the changes in an individual's disease progression and health care history. In medical practice, nested test-and-treat strategies are common to improve cost-effectiveness. For example, for patients at risk of prostate cancer, only patients who have high prostate-specific antigen (PSA) need a biopsy, which is costly and invasive, to confirm the diagnosis and help determine the treatment if needed. A decision about treatment happens after the biopsy, and is thus nested within the decision of whether to do the test. However, current existing statistical methods are not able to accommodate such a naturally embedded property of the treatment decision within the test decision. Therefore, we developed a new statistical learning method, step-adjusted tree-based reinforcement learning, to evaluate DTRs within such a nested multistage dynamic decision framework using observational data. At each step within each stage, we combined the robust semiparametric estimation via augmented inverse probability weighting with a tree-based reinforcement learning method to deal with the counterfactual optimization. The simulation studies demonstrated robust performance of the proposed methods under different scenarios. We further applied our method to evaluate the necessity of prostate biopsy and identify the optimal test-and-treat regimes for prostate cancer patients using data from the Johns Hopkins University prostate cancer active surveillance dataset.

A fecal-based test for the detection of advanced adenoma and colorectal cancer: a case-control and screening cohort study

BACKGROUND

Colorectal cancer (CRC) is the leading cause of cancer death worldwide. Screening is a confirmed way to reduce the incidence and mortality rates of CRC. This study aimed to identify a fecal-based, noninvasive, and accurate method for detection of colorectal cancer (CRC) and advanced adenoma (AA).

METHODS

Through detection in tissue (n = 96) and fecal samples (n = 88) and tested in an independent group of fecal samples (n = 294), the methylated DNA marker ITGA4 and bacterial markers Fusobacterium nucleatum (Fn) and Pepetostreptococcusanaerobius (Pa) were identified from the candidate biomarkers for CRC and AA detection. A prediction score (pd-score) was constructed using the selected markers and fecal immunochemical test (FIT) for distinguishing AA and CRC from healthy subjects by logistic regression method. The diagnostic performance of the pd-score was compared with FIT and validated in the external validation cohort (n = 117) and in a large CRC screening cohort.

RESULTS

The pd-score accurately identified AA and CRC from healthy subjects with an area under the curve (AUC) of 0.958, at a specificity of 91.37%; the pd-score showed sensitivities of 95.38% for CRC and 70.83% for AA, respectively. In the external validation cohort, the sensitivities of the pd-score for CRC and AA detection were 94.03% and 80.00%, respectively. When applied in screening, the pd-score identified 100% (11/11) of CRC and 70.83% (17/24) of AA in participants with both colonoscopy results and qualified fecal samples, showing an improvement by 41.19% compared to FIT.

CONCLUSIONS

The current study developed a noninvasive and well-validated approach for AA and CRC detection, which could be applied widely as a diagnostic and screening test.

Multiple Biomarker-Combined Screening for Colorectal Cancer Based on Bisulfate Conversion-Free Detection of Fecal DNA Methylation

To evaluate the applicability of bisulfate conversion-free methylation assay based on enzyme digestion in fecal screening for colorectal cancer (CRC). Stool samples were collected from a total of 1142 participants with intestinal abnormalities, including 180 positive cases, 60 advanced adenomas, and 902 negative cases. DNA from reference cell lines and clinical samples was extracted and digested with an enzyme to detect the methylation of CRC markers SEPT9, SDC2, NDRG4, SFRP2, and BMP3 genes. Statistical analysis was then used to determine the ability of the markers, both individually and in combination, to detect CRC and adenoma. Our results showed that the enzyme digestion method could suitably detect DNA marker methylation in as low as 1% of the cell lines. BMP3 had a considerably low detection rate in all clinical samples, with only 6 positive cases detected out of 180 cancer samples. Our findings showed that the combination of SEPT9, SDC2, and SFRP2 had an area under the receiver operation curve of 0.937, sensitivity of 94.11%, and specificity of 89.21% for detecting CRC. Moreover, the detection sensitivity of adenoma can also reach 38.33%. After innovatively utilizing bisulfate conversion-free methylation assay for CRC screening, this study verified the potential clinical applicability of combining multiple biomarkers for CRC screening in a large number of samples.

Advances in colorectal cancer genomics and transcriptomics drive early detection and prevention

Colorectal carcinoma (CRC) is a high incidence cancer and leading cause of cancer mortality worldwide. The advances in genomics and transcriptomics in the past decades have improved the detection and prevention of CRC in familial CRC syndromes. Nevertheless, the ultimate goal of personalized medicine for sporadic CRC is still not within reach due no less to the difficulty in integrating population disparity and clinical data to combat what essentially is a very heterogenous disease. This minireview highlights the achievement of the past decades and present possible direction in the hope of early detection and metastasis prevention for reducing CRC-associated morbidity and mortality.

Performance evaluation of stool DNA methylation tests in colorectal cancer screening: a systematic review and meta-analysis

AIM

There is not sufficient evidence about whether stool DNA methylation tests allow prioritizing patients to colonoscopy. Due to the COVID-19 pandemic, there will be a wait-list for rescheduling colonoscopies once the mitigation is lifted. The aim of this meta-analysis was to evaluate the accuracy of stool DNA methylation tests in detecting colorectal cancer.

METHODS

The PubMed, Cochrane Library and MEDLINE via Ovid were searched. Studies reporting the accuracy (Sackett phase 2 or 3) of stool DNA methylation tests to detect sporadic colorectal cancer were included. The DerSimonian-Laird method with random-effects model was utilized for meta-analysis.

RESULTS

Forty-six studies totaling 16 149 patients were included in the meta-analysis. The pooled sensitivity and specificity of all single genes and combinations was 62.7% (57.7%, 67.4%) and 91% (89.5%, 92.2%), respectively. Combinations of genes provided higher sensitivity compared to single genes (80.8% [75.1%, 85.4%] vs. 57.8% [52.3%, 63.1%]) with no significant decrease in specificity (87.8% [84.1%, 90.7%] vs. 92.1% [90.4%, 93.5%]). The most accurate single gene was found to be SDC2 with a sensitivity of 83.1% (72.6%, 90.2%) and a specificity of 91.2% (88.6%, 93.2%).

CONCLUSIONS

Stool DNA methylation tests have high specificity (92%) with relatively lower sensitivity (81%). Combining genes increases sensitivity compared to single gene tests. The single most accurate gene is SDC2, which should be considered for further research.

Epigenetic alterations in the gastrointestinal tract: Current and emerging use for biomarkers of cancer

Colorectal cancer is a leading cause of cancer related deaths worldwide. One of the hallmarks of cancer and a fundamental trait of virtually all gastrointestinal cancers is genomic and epigenomic DNA alterations. Cancer cells acquire genetic and epigenetic alterations that drive the initiation and progression of the cancers by altering the molecular and cell biological process of the cells. These alterations, as well as other host and microenvironment factors, ultimately mediate the initiation and progression of cancers, including colorectal cancer. Epigenetic alterations, which include changes affecting DNA methylation, histone modifications, chromatin structure, and noncoding RNA expression, have emerged as a major class of molecular alteration in colon polyps and colorectal cancer. The classes of epigenetic alterations, their status in colorectal polyps and cancer, their effects on neoplasm biology, and their application to clinical care will be discussed.

Epigenetic Alterations in the Gastrointestinal Tract: Current and Emerging Use for Biomarkers of Cancer

Colorectal cancer, liver cancer, stomach cancer, pancreatic cancer, and esophageal cancer are leading causes of cancer-related deaths worldwide. A fundamental trait of virtually all gastrointestinal cancers is genomic and epigenomic DNA alterations. Cancer cells acquire genetic and epigenetic alterations that drive the initiation and progression of the cancers by altering the molecular and cell biological processes of the cells. These alterations, as well as other host and microenvironment factors, ultimately mediate the clinical behavior of the precancers and cancers and can be used as biomarkers for cancer risk determination, early detection of cancer and precancer, determination of the prognosis of cancer and prediction of the response to therapy. Epigenetic alterations have emerged as one of most robust classes of biomarkers and are the basis for a growing number of clinical tests for cancer screening and surveillance.

DNA methylation markers detected in blood, stool, urine, and tissue in colorectal cancer: a systematic review of paired samples

PURPOSE

Methylated cell-free DNA in liquid biopsies are promising non-invasive biomarkers for colorectal cancer (CRC). Optimal markers would have high sensitivity and specificity for early detection of CRC and could be detected in more than one type of material from the patient. We systematically reviewed the literature on DNA methylation markers of colorectal cancer, detected in more than one type of material, regarding their potential as contributors to a panel for screening and follow-up of CRC.

METHODS

The databases MEDLINE, Web of Science, and Embase were systematically searched. Data extraction and review was performed by two authors independently. Agreement between methylation status in tissue and other materials (blood/stool/urine) was analyzed using the McNemar test and Cohen's kappa.

RESULTS

From the 51 included studies, we identified seven single markers with sensitivity ≥ 75% and specificity ≥ 90% for CRC. We also identified one promising plasma panel and two stool panels. The correspondence of methylation status was evaluated as very good for four markers, but only marginal for most of the other markers investigated (12 of 21).

CONCLUSION

The included studies reported only some of the variables and markers of interest and included few patients. Hence, a meta-analysis was not possible at this point. Larger, prospective studies must be designed to study the discordant detection of markers in tissue and liquid biopsies. When reporting their findings, such studies should use a standardized format.

Biomarkers for Early Detection of Colorectal Cancer: The Early Detection Research Network, a Framework for Clinical Translation

Early detection by screening significantly reduces mortality from colorectal cancer, but 40% of guideline-eligible patients are not screened as recommended in the United States. Novel strategies to improve screening uptake overall and efforts to deploy best practices to underserved populations are a high priority for health care. This review focuses on existing biomarkers in practice and those in development with clinical relevance to early detection of colorectal neoplasia, with an emphasis on those developed by investigators of the NCI's Early Detection Research Network. Aberrantly methylated DNA markers (blood and stool), stool-based markers (including fecal immunochemical test-DNA), and a variety of blood-based marker assays in development (protein markers, glycoproteins including mucins, and cell-free DNA tests) are reviewed. Individual markers and biomarker panels, sample resources, and barriers to translating biomarkers to clinical practice are discussed.See all articles in this CEBP Focus section, "NCI Early Detection Research Network: Making Cancer Detection Possible."

Robust performance of a novel stool DNA test of methylated SDC2 for colorectal cancer detection: a multicenter clinical study

BACKGROUND AND AIMS

Stool DNA testing is an emerging and attractive option for colorectal cancer (CRC) screening. We previously evaluated the feasibility of a stool DNA (sDNA) test of methylated SDC2 for CRC detection. The aim of this study was to assess its performance in a multicenter clinical trial setting.

METHODS

Each participant was required to undergo a sDNA test and a reference colonoscopy. The sDNA test consists of quantitative assessment of methylation status of SDC2 promoter. Results of real-time quantitative methylation-specific PCR were dichotomized as positive and negative, and the main evaluation indexes were sensitivity, specificity, and kappa value. All sDNA tests were performed and analyzed independently of colonoscopy.

RESULTS

Among the 1110 participants from three clinical sites analyzed, 359 and 38 were diagnosed, respectively, with CRC and advanced adenomas by colonoscopy. The sensitivity of the sDNA test was 301/359 (83.8%) for CRC, 16/38 (42.1%) for advanced adenomas, and 134/154 (87.0%) for early stage CRC (stage I-II). Detection rate did not vary significantly according to age, tumor location, differentiation, and TNM stage, except for gender. The follow-up testing of 40 postoperative patients with CRC returned negative results as their tumors had been surgically removed. The specificity of the sDNA test was 699/713 (98.0%), and unrelated cancers and diseases did not seem to interfere with the testing. The kappa value was 0.84, implying an excellent diagnostic consistency between the sDNA test and colonoscopy.

CONCLUSION

Noninvasive sDNA test using methylated SDC2 as the exclusive biomarker is a clinically viable and accurate CRC detection method.

CHINESE CLINICAL TRIAL REGISTRY

Chi-CTR-TRC-1900026409, retrospectively registered on October 8, 2019; http://www.chictr.org.cn/edit.aspx?pid=43888&htm=4 .

Fecal DNA methylation markers for detecting stages of colorectal cancer and its precursors: a systematic review

Background

DNA methylation biomarkers in stool may have applications in early colorectal cancer (CRC) detection; however, their association with stages of CRC carcinogenesis or their performance in detecting various stages is unclear. We aimed to systematically review the evidence for DNA methylation markers in stool for risk stratification or detection of specific CRC stages, as well as precursors of CRC.

Methods

We conducted a systematic search in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched PubMed and ISI Web of Knowledge to identify relevant studies published until 14th January 2020. Two reviewers independently extracted data on study population characteristics, candidate genes, methylation measurement methods, odds ratios (ORs), overall and stage-specific sensitivities, specificities, areas under the receiver operating characteristics curve, and p-values for statistical significance for OR and for association of methylation levels with stage.

Results

Twenty-seven studies that reported stage-specific associations or performances of fecal DNA methylation markers for detecting colorectal neoplasms were identified. All studies used methylation-specific polymerase chain reaction for assessing methylation levels in the promoter or exon 1 regions of targeted genes. However, most studies were underpowered and limited by their case-control design. Furthermore, the stage-specific associations or sensitivities were validated for two markers (hypermethylation of GATA4 and VIM) only.

Conclusion

Methylation markers in stool may be useful for detection of CRC precursors or CRC staging, but promising candidate markers need to be validated in longitudinal studies on large screening populations, performing epigenome-wide analyses. Identification of stage-specific DNA methylation biomarkers in stool could boost current strategies towards early detection and enable different approaches to precision medicine for CRC.

Novel biomarkers for the diagnosis and prognosis of colorectal cancer

Colorectal cancer (CRC) is among the most common malignancies and remains a major cause of cancer-related death worldwide. Despite recent advances in surgical and multimodal therapies, the overall survival of advanced CRC patients remains very low. Cancer progression, including invasion and metastasis, is a major cause of death among CRC patients. The underlying mechanisms of action resulting in cancer progression are beginning to unravel. The reported molecular and biochemical mechanisms that might contribute to the phenotypic changes in favor of carcinogenesis include apoptosis inhibition, enhanced tumor cell proliferation, increased invasiveness, cell adhesion perturbations, angiogenesis promotion, and immune surveillance inhibition. These events may contribute to the development and progression of cancer. A biomarker is a molecule that can be detected in tissue, blood, or stool samples to allow the identification of pathological conditions such as cancer. Thus, it would be beneficial to identify reliable and practical molecular biomarkers that aid in the diagnostic and therapeutic processes of CRC. Recent research has targeted the development of biomarkers that aid in the early diagnosis and prognostic stratification of CRC. Despite that, the identification of diagnostic, prognostic, and/or predictive biomarkers remains challenging, and previously identified biomarkers might be insufficient to be clinically applicable or offer high patient acceptability. Here, we discuss recent advances in the development of molecular biomarkers for their potential usefulness in early and less-invasive diagnosis, treatment, and follow-up of CRC.

DNA methylation biomarkers in stool for early screening of colorectal cancer

Objective: Detection of aberrant methylated genes in feces has been developed as an early screening method for colorectal cancer. The aim of this study was to probe the methylation status of SEPT9, BMP3, NDRG4, and SDC2 in stool and study whether methylation of these genes is associated with colorectal cancer. Materials and Methods: DNAs were isolated and purified from cancerous and non-cancerous stool samples and colorectal cancer tissue. Gene methylation levels were quantified by methylation-specific PCR on SEPT9, BMP3, NDRG4, and SDC2 and analyzed by a diagnostic model. Results: DNA methylation of SEPT9, NDRG4 and SDC2, but not BMP3, had diagnostic potential for detecting colorectal cancer. Moreover, integration of SEPT9, NDRG4, and SDC2 methylation demonstrated high feasibility for detecting colorectal cancer and adenoma, with better performance on colorectal cancer than adenoma. Conclusion: The methylation of SEPT9, NDRG4, and SDC2 in stool may be a potential biomarker for early screening of colorectal cancer.

A Simple and Highly Specific MassARRAY-Based Stool DNA Assay to Prioritize Follow-up Decisions in Fecal Immunochemical Test-Positive Individuals

BACKGROUND

Seventy-five percent of fecal immunochemical test (FIT)-positive individuals are false positives and undergo unnecessary colonoscopies. Here, we established a stool DNA (sDNA) test that uses the Single Allele Base Extension Reaction (SABER) MassARRAY platform to improve the accuracy of FIT-based CRC detection.

METHODS

Twenty-one variants in five CRC-associated genes were selected for the sDNA panel. Cell line DNA and matched mutation-confirmed tissue and stool samples from 34 patients were used for accuracy assessment (cohort 1). The clinical performance of the sDNA assay was further evaluated in 101 independent FIT-positive stool samples (cohort 2).

RESULTS

In cohort 1, we obtained a 62% mutation concordance rate in paired tissue and stool samples of the CRC group, regardless of the FIT status. In cohort 2, 100% specificity in normal controls with positive FIT results was observed. By weighting the FIT value and the presence of a given variant type in stool and then summing the two scores, we found that a one-increment increase in the score was associated with a 4.538-fold risk (95% CI = 2.121⁻9.309) for malignancy in the FIT-positive setting.

CONCLUSIONS

Our highly specific sDNA assay can help prioritize the most at-risk FIT-positive persons to receive prompt colonoscopic confirmation of CRC.

Prognostic and Predictive Epigenetic Biomarkers in Oncology

Epigenetic patterns, such as DNA methylation, histone modifications, and non-coding RNAs, can be both driver factors and characteristic features of certain malignancies. Aberrant DNA methylation can lead to silencing of crucial tumor suppressor genes or upregulation of oncogene expression. Histone modifications and chromatin spatial organization, which affect transcription, regulation of gene expression, DNA repair, and replication, have been associated with multiple tumors. Certain microRNAs (miRNAs), mainly those that silence tumor suppressor genes and occur in a greater number of copies, have also been shown to promote oncogenesis. Multiple patterns of these epigenetic factors occur specifically in certain malignancies, which allows their potential use as biomarkers. This review presents examples of tests for each group of epigenetic factors that are currently available or in development for use in early cancer detection, prediction, prognosis, and response to treatment. The availability of blood-based biomarkers is noted, as they allow sampling invasiveness to be reduced and the sampling procedure to be simplified. The article stresses the role of epigenetics as a crucial element of future cancer diagnostics and therapy.

A systematic review and quantitative assessment of methylation biomarkers in fecal DNA and colorectal cancer and its precursor, colorectal adenoma

Colorectal cancer (CRC) arises from accumulated genetic and epigenetic alterations, which provide the possibility to identify tumor-specific biomarkers by analyzing fecal DNA. Methylation status in human genes from tumor tissue is highlighted as promising biomarker in the early detection of CRC. A number of studies have documented altered methylation levels in DNA extracted from stool samples, but generated heterogeneous results. We performed a systematic review and quantitative assessment of existing studies to compare levels of DNA methylation in most frequently studied genes and their diagnostic value in CRC and its precursor, colorectal adenoma, with their counterparts in healthy subjects. Robust searches of the literature were performed in our study with explicit strategies and definite inclusion/exclusion criteria. Pooled data revealed that methylation levels of SFRP2, SFRP1, TFPI2, BMP3, NDRG4, SPG20, and BMP3 plus NDRG4 genes exceeded a sensitivity of 70% and a specificity of 80% for CRC detection. The DOR of the seven candidate biomarkers ranged from 19.80 to 334.33, indicating a good diagnostic power in discriminating cancer from normal tissues. The AUC range was from 0.88 to 0.95, indicating a good or very good discriminatory performance. When test results for BMP3 and NDRG4 were combined, the DOR of CRC detection was 98.36, which was higher than that for BMP3 and NDRG4 separately. As for adenoma detection, the DOR of methylated NDRG4 is higher than that for CRC (CRC vs. adenoma: 54.86 vs. 57.22). Both the sensitivity and specificity of NDRG4 for adenoma detection exceeded 70%. These findings demonstrate the eligibility and feasibility of DNA methylation as a minimally invasive biomarker in feces in the diagnosis of CRC and adenoma. The use of DNA from human stools has the potential to be readily applicable to detect aberrant DNA methylation levels among many subjects for CRC early screening.

Biomarkers in colorectal cancer: Current clinical utility and future perspectives

Colorectal cancer (CRC) is a major cause of cancer death worldwide. CRC has poor prognosis and there is a crucial need for new diagnostic and prognostic biomarkers to avoid CRC-related deaths. CRC can be considered a sporadic disease in most cases (75%-80%), but it has been suggested that crosstalk between gene mutations (i.e., mutations of BRAF, KRAS, and p53 as well as microsatellite instability) and epigenetic alterations (i.e., DNA methylation of CpG island promoter regions) could play a pivotal role in cancer development. A number of studies have focused on molecular testing to guide targeted and conventional treatments for patients with CRC, sometimes with contrasting results. Some of the most useful innovations in the management of CRC include the possibility to detect the absence of KRAS, BRAF, NRAS and PIK3CA gene mutations with the subsequent choice to administer targeted adjuvant therapy with anti-epidermal growth factor receptor antibodies. Moreover, CRC patients can benefit from tests for microsatellite instability and for the detection of loss of heterozygosity of chromosome 18q that can be helpful in guiding therapeutic decisions as regards the administration of 5-FU. The aim of this review was to summarize the most recent evidence on the possible use of genetic or epigenetic biomarkers for diagnosis, prognosis and response to therapy in CRC patients.

The importance of stool DNA methylation in colorectal cancer diagnosis: A meta-analysis

A large number of tumor-related methylated genes have been suggested to be of diagnostic and prognostic values for CRC when analyzed in patients' stool samples; however, reported sensitivities and specificities have been inconsistent and widely varied. This meta-analysis was conducted to assess the detection accuracy of stool DNA methylation assay in CRC, early stages of CRC (advanced adenoma, non-advanced adenomas) and hyperplastic polyps, separately. We searched MEDLINE, Web of Science, Scopus and Google Scholar databases until May 1, 2016. From 469 publications obtained in the initial literature search, 38 studies were included in the final analysis involving 4867 individuals. The true positive, false positive, true negative and false negative of a stool-based DNA methylation biomarker using all single-gene tests considering a certain gene; regardless of a specific gene were pooled and studied in different categories. The sensitivity of different genes in detecting different stages of CRC ranged from 0% to 100% and the specificities ranged from 73% to 100%. Our results elucidated that SFRP1 and SFRP2 methylation possessed promising accuracy for detection of not only CRC (DOR: 31.67; 95%CI, 12.31-81.49 and DOR: 35.36; 95%CI, 18.71-66.84, respectively) but also the early stages of cancer, adenoma (DOR: 19.72; 95%CI, 6.68-58.25 and DOR: 13.20; 95%CI, 6.01-28.00, respectively). Besides, NDRG4 could be also considered as a significant diagnostic marker gene in CRC (DOR: 24.37; 95%CI, 10.11-58.73) and VIM in adenoma (DOR: 15.21; 95%CI, 2.72-85.10). In conclusion, stool DNA hypermethylation assay based on the candidate genes SFRP1, SFRP2, NDRG4 and VIM could offer potential diagnostic value for CRC based on the findings of this meta-analysis.

Improving diagnosis, prognosis and prediction by using biomarkers in CRC patients (Review)

Colorectal cancer (CRC) is among the most common cancers. In fact, it is placed in the third place among the most diagnosed cancer in men, after lung and prostate cancer, and in the second one for the most diagnosed cancer in women, following breast cancer. Moreover, its high mortality rates classifies it among the leading causes of cancer‑related death worldwide. Thus, in order to help clinicians to optimize their practice, it is crucial to introduce more effective tools that will improve not only early diagnosis, but also prediction of the most likely progression of the disease and response to chemotherapy. In that way, they will be able to decrease both morbidity and mortality of their patients. In accordance with that, colon cancer research has described numerous biomarkers for diagnostic, prognostic and predictive purposes that either alone or as part of a panel would help improve patient's clinical management. This review aims to describe the most accepted biomarkers among those proposed for use in CRC divided based on the clinical specimen that is examined (tissue, faeces or blood) along with their restrictions. Lastly, new insight in CRC monitoring will be discussed presenting promising emerging biomarkers (telomerase activity, telomere length and micronuclei frequency).

Is methylation analysis of SFRP2, TFPI2, NDRG4, and BMP3 promoters suitable for colorectal cancer screening in the Korean population?

Background/Aims

Colorectal cancer (CRC) screening using stool DNA was recently found to yield good detection rates. A multi-target stool DNA test (Cologuard®, Exact Sciences), including methylated genes has been recently approved by the U.S. Food and Drug Administration. The aim of this study was to validate these aberrantly methylated genes as stool-based DNA markers for detecting CRC and colorectal advanced adenoma (AA) in the Korean population.

Methods

A single-center study was conducted in 36 patients with AA; 35 patients with CRC; and 40 endoscopically diagnosed healthy controls using CRC screening colonoscopy. The methylation status of the SFRP2, TFPI2, NDRG4, and BMP3 promoters was investigated blindly using bisulfate-modified stool DNA obtained from 111 participants. Methylation status was investigated by methylation-specific polymerase chain reaction.

Results

Methylated SFRP2, TFPI2, NDRG4, and BMP3 promoters were detected in 60.0%, 31.4%, 68.8%, and 40.0% of CRC samples and in 27.8%, 27.8%, 27.8%, and 33.3% of AA samples, respectively. The sensitivities obtained using 4 markers to detect CRC and AA were 94.3% and 72.2%, respectively. The specificity was 55.0%.

Conclusions

Our results demonstrate that the SFRP2, TFPI2, NDRG4, and BMP3 promoter methylation analysis of stool sample DNA showed high sensitivity but low specificity for detecting CRC and AA. Because of the low specificity, 4 methylated markers might not be sufficient for CRC screening in the Korean population. Further large-scale studies are required to validate the methylation of these markers in the Asian population and to find new markers for the Asian population.

Non-coding RNAs as Biomarkers for Colorectal Cancer Screening and Early Detection

Early detection of colorectal cancer (CRC) is the key for prevention and the ability to impact long-term survival of CRC patients. Current CRC screening modalities are inadequate for global application because of low sensitivity and specificity in case of conventional stool-based screening tests, and high costs and a low participation compliance in colonoscopy. An accurate stool- or blood-based screening test with use of innovative biomarkers is an appealing alternative as it is non-invasive and poses minimal risk to patients. It is easy to perform, can be repeated at shorter intervals, and therefore would likely lead to a much higher compliance rates. Non-coding RNAs (ncRNAs) have recently gained attention because of their involvement in different biological processes, such as proliferation, differentiation, migration, angiogenesis and apoptosis. An increasing number of studies have demonstrated that mutations or abnormal expression of ncRNAs are closely associated with various cancers, including CRC. The discovery that ncRNAs (mainly microRNAs) are stable in stool and in blood plasma and serum presents the opportunity to develop novel strategies taking advantage of circulating ncRNAs as early diagnostic biomarkers of CRC. This chapter is a comprehensive examination of aberrant ncRNAs expression levels in tumor tissue, stool and blood of CRC patients and a summary of the current findings on ncRNAs, including microRNAs, small nucleolar RNAs, small nuclear RNAs, Piwi-interacting RNAs, circular RNAs and long ncRNAs in regards to their potential usage for screening or early detection of CRC.

The role of Nrf2-Keap1 axis in colorectal cancer, progression, and chemoresistance

Colorectal cancer is the third common cancer after lung and genital cancers worldwide with more than 1.2 million new cases diagnosed annually. Although extensive progress has been made in the treatment of colorectal cancer, finding novel targets for early diagnosis and effective treatment of these patients is an urgent need. Nuclear factor-erythroid 2-kelch-like ECH-associated protein 1 signaling pathway plays a key role in protecting cells from the damage of intracellular oxidative stress and extracellular oxidizing agents. Nuclear factor-erythroid 2 is a transcription factor that creates intracellular redox homeostasis via transcriptional activity and interaction with kelch-like ECH-associated protein 1. Furthermore, it contributes to survival and chemoresistance of colorectal cancer cells which is mediated by overexpression of cytoprotective and multidrug resistance genes. In this review, the dual role of nuclear factor-erythroid 2 signaling in induction of colorectal cancer cell survival and death as well as the possibility of targeting nuclear factor-erythroid 2-kelch-like ECH-associated protein 1 axis as an advanced strategy in prevention and effective treatment of colorectal cancer patients have been discussed.

Colorectal Cancer Screening: Stool DNA and Other Noninvasive Modalities

Colorectal cancer screening dates to the discovery of pre-cancerous adenomatous tissue. Screening modalities and guidelines directed at prevention and early detection have evolved and resulted in a significant decrease in the prevalence and mortality of colorectal cancer via direct visualization or using specific markers. Despite continued efforts and an overall reduction in deaths attributed to colorectal cancer over the last 25 years, colorectal cancer remains one of the most common causes of malignancy-associated deaths. In attempt to further reduce the prevalence of colorectal cancer and associated deaths, continued improvement in screening quality and adherence remains key. Noninvasive screening modalities are actively being explored. Identification of specific genetic alterations in the adenoma-cancer sequence allow for the study and development of noninvasive screening modalities beyond guaiac-based fecal occult blood testing which target specific alterations or a panel of alterations. The stool DNA test is the first noninvasive screening tool that targets both human hemoglobin and specific genetic alterations. In this review we discuss stool DNA and other commercially available noninvasive colorectal cancer screening modalities in addition to other targets which previously have been or are currently under study.

Molecular Biomarkers of Colorectal Cancer and Cancer Disparities: Current Status and Perspective

This review provides updates on the efforts for the development of prognostic and predictive markers in colorectal cancer based on the race/ethnicity of patients. Since the clinical consequences of genetic and molecular alterations differ with patient race and ethnicity, the usefulness of these molecular alterations as biomarkers needs to be evaluated in different racial/ethnic groups. To accomplish personalized patient care, a combined analysis of multiple molecular alterations in DNA, RNA, microRNAs (miRNAs), metabolites, and proteins in a single test is required to assess disease status in a precise way. Therefore, a special emphasis is placed on issues related to utility of recently identified genetic and molecular alterations in genes, miRNAs, and various "-omes" (e.g., proteomes, kinomes, metabolomes, exomes, methylomes) as candidate molecular markers to determine cancer progression (disease recurrence/relapse and metastasis) and to assess the efficacy of therapy in colorectal cancer in relation to patient race and ethnicity. This review will be useful for oncologists, pathologists, and basic and translational researchers.

Establishing the clinical utility of epigenetic markers in cancer: many challenges ahead

The use of epigenetic biomarkers in cancer management relies on the availability of robust assays and evidence that these markers are able to segregate clinically significant groups of patients. While many cancers are characterized by genetic and epigenetic modifications, it is far simpler to develop molecular tests that detect genetic rather than epigenetic changes. In this special report, we will describe the challenges associated with developing epigenetic assays and the practical issues that must be overcome before they can be used in the clinic.

The Diagnostic Performance of Stool DNA Testing for Colorectal Cancer: A Systematic Review and Meta-Analysis

This meta-analysis was designed to evaluate the diagnostic performance of stool DNA testing for colorectal cancer (CRC) and compare the performance between single-gene and multiple-gene tests.MEDLINE, Cochrane, EMBASE databases were searched using keywords colorectal cancers, stool/fecal, sensitivity, specificity, DNA, and screening. Sensitivity analysis, quality assessments, and performance bias were performed for the included studies.Fifty-three studies were included in the analysis with a total sample size of 7524 patients. The studies were heterogeneous with regard to the genes being analyzed for fecal genetic biomarkers of CRC, as well as the laboratory methods being used for each assay. The sensitivity of the different assays ranged from 2% to 100% and the specificity ranged from 81% to 100%. The meta-analysis found that the pooled sensitivities for single- and multigene assays were 48.0% and 77.8%, respectively, while the pooled specificities were 97.0% and 92.7%. Receiver operator curves and diagnostic odds ratios showed no significant difference between both tests with regard to sensitivity or specificity.This meta-analysis revealed that using assays that evaluated multiple genes compared with single-gene assays did not increase the sensitivity or specificity of stool DNA testing in detecting CRC.

Serum Unsaturated Free Fatty Acids: A Potential Biomarker Panel for Early-Stage Detection of Colorectal Cancer

Background: To screen biomarkers to differentiate early-stage colorectal cancer (CRC) from benign colorectal disease (BCD) and healthy controls.

Materials & Methods: Quantitative and qualitative analysis of C_16:1, C_18:3, C_18:2, C_18:1, C_20:4, and C_22:6 in 185 healthy controls, 55 patients with BCD, and 139 patients with CRC was performed. Comparisons of their levels in between CRC patients, BCD patients, and healthy controls were performed using Mann-Whitney U test.

Results: Serum levels of C_16:1, C_18:3, C_18:2, C_18:1, C_20:4, and C_22:6 in CRC patients were significantly decreased compared with healthy controls and BCD patients. A combination of C_16:1, C_18:2, C_20:4, and C_22:6 has excellent diagnostic performance to differentiate early-stage CRC patients from healthy controls plus BCD patients, with an AUC of 0.926, a sensitivity of 84.6%, and a specificity of 89.8%.

Conclusions: Serum levels of C_16:1, C_18:2, C_20:4, and C_22:6 could be diagnostic indicators of early-stage CRC patients.

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.

Characterization of DNA Methylation in Circulating Tumor Cells

Epigenetics contributes to molecular mechanisms leading to tumor cell transformation and systemic progression of cancer. However, the dynamics of epigenetic remodeling during metastasis remains unexplored. In this context, circulating tumor cells (CTCs) might enable a direct insight into epigenetic mechanisms relevant for metastasis by providing direct access to systemic cancer. CTCs can be used as prognostic markers in cancer patients and are regarded as potential metastatic precursor cells. However, despite substantial technical progress, the detection and molecular characterization of CTCs remain challenging, in particular the analysis of DNA methylation. As recent studies have started to address the epigenetic state of CTCs, we discuss here the potential of such investigations to elucidate mechanisms of metastasis and to develop tumor biomarkers.

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.

Epigenetic Alterations in Colorectal Cancer: Emerging Biomarkers

Colorectal cancer (CRC) is a leading cause of cancer deaths worldwide. One of the fundamental processes driving the initiation and progression of CRC is the accumulation of a variety of genetic and epigenetic changes in colonic epithelial cells. Over the past decade, major advances have been made in our understanding of cancer epigenetics, particularly regarding aberrant DNA methylation, microRNA (miRNA) and noncoding RNA deregulation, and alterations in histone modification states. Assessment of the colon cancer "epigenome" has revealed that virtually all CRCs have aberrantly methylated genes and altered miRNA expression. The average CRC methylome has hundreds to thousands of abnormally methylated genes and dozens of altered miRNAs. As with gene mutations in the cancer genome, a subset of these epigenetic alterations, called driver events, are presumed to have a functional role in CRC. In addition, the advances in our understanding of epigenetic alterations in CRC have led to these alterations being developed as clinical biomarkers for diagnostic, prognostic, and therapeutic applications. Progress in this field suggests that these epigenetic alterations will be commonly used in the near future to direct the prevention and treatment of CRC.

Strategies for validation and testing of DNA methylation biomarkers

DNA methylation is a stable covalent epigenetic modification of primarily CpG dinucleotides that has recently gained considerable attention for its use as a biomarker in different clinical settings, including disease diagnosis, prognosis and therapeutic response prediction. Although the advent of genome-wide DNA methylation profiling in primary disease tissue has provided a manifold resource for biomarker development, only a tiny fraction of DNA methylation-based assays have reached clinical testing. Here, we provide a critical overview of different analytical methods that are suitable for biomarker validation, including general study design considerations, which might help to streamline epigenetic marker development. Furthermore, we highlight some of the recent marker validation studies and established markers that are currently commercially available for assisting in clinical management of different cancers.

The molecular pathogenesis of colorectal cancer and its potential application to colorectal cancer screening

INTRODUCTION

Advances in our understanding of the molecular genetics and epigenetics of colorectal cancer have led to novel insights into the pathogenesis of this common cancer. These advances have revealed that there are molecular subtypes of colon polyps and colon cancer and that these molecular subclasses have unique and discrete clinical and pathological features. Although the molecular characterization of these subgroups of colorectal polyps and cancer is only partially understood at this time, it does appear likely that classifying colon polyps and cancers based on their genomic instability and/or epigenomic instability status will eventually be useful for informing approaches for the prevention and early detection of colon polyps and colorectal cancer.

CONCLUSIONS

In this review, we will discuss our current understanding of the molecular pathogenesis of the polyp to cancer sequence and the potential to use this information to direct screening and prevention programs.

Early detection of colorectal cancer: from conventional methods to novel biomarkers

PURPOSE

Colorectal cancer (CRC) is one of the major health problems worldwide and is often diagnosed at late stage. There is growing body of evidence in early detection of this disease with novel screening modalities to reduce compliance and increase specificity of available methods. The aim of current review is to give an overview on currently available screening methods (e.g., fecal occult blood testing (FOBT), flexible sigmoidoscopy, and colonoscopy), with their own merits and disadvantages, and new genetic/epigenetic/protein markers, as novel screening modalities.

RESULT

There are several serum and fecal biomarkers that can predict CRC and polyps. Overall sensitivities for detection by fecal DNA markers ranged from 53 to 87%, while a panel of serum protein markers provides a sensitivity/specificity up to 85% for CRC. In particular, DNA methylation markers (e.g., SEPT9, SFRP2, and ALX4), circulating microRNAs (e.g., microRNA21), SNPs in microRNAs binding site (e.g., rs4596 located within a target region of the predicted miR-518a-5p and miR-527), protein markers (e.g., carcinoembryonic antigen, N-methyltransferase), or microsatellites instability in tumors with deficient mismatch repair of some genes are among the most interesting and promising biomarkers.

CONCLUSION

Increasing evidence supports the use of combined fecal and serum biomarkers with sigmoidoscopy and colonoscopy screening in order to maximize the benefits and reduce the number of false-positive tests and patients undergoing invasive methods, which in turn could overcome the limitations of the current screening methods for early detection of CRC and adenomas.

Promoter hypermethylation of tumour suppressor genes as potential biomarkers in colorectal cancer

Colorectal cancer (CRC) is a common malignancy and the fourth leading cause of cancer deaths worldwide. It results from the accumulation of multiple genetic and epigenetic changes leading to the transformation of colon epithelial cells into invasive adenocarcinomas. In CRC, epigenetic changes, in particular promoter CpG island methylation, occur more frequently than genetic mutations. Hypermethylation contributes to carcinogenesis by inducing transcriptional silencing or downregulation of tumour suppressor genes and currently, over 600 candidate hypermethylated genes have been identified. Over the past decade, a deeper understanding of epigenetics coupled with technological advances have hinted at the potential of translating benchtop research into biomarkers for clinical use. DNA methylation represents one of the largest bodies of literature in epigenetics, and hence has the highest potential for minimally invasive biomarker development. Most progress has been made in the development of diagnostic markers and there are currently two, one stool-based and one blood-based, biomarkers that are commercially available for diagnostics. Prognostic and predictive methylation markers are still at their infantile stages.

The role of epigenetics in colorectal cancer

Colorectal cancer (CRC) results from a stepwise accumulation of genetic and epigenetic alterations that transform the normal colonic epithelium into cancer. DNA methylation represents one of the most studied epigenetic marks in CRC, and three common epigenotypes have been identified characterized by high, intermediate and low methylation profiles, respectively. Combining DNA methylation data with gene mutations and cytogenetic alterations occurring in CRC is nowadays allowing the characterization of different CRC subtypes, but the crosstalk between DNA methylation and other epigenetic mechanisms, such as histone tail modifications and the deregulated expression of non-coding RNAs is not yet clearly defined. Epigenetic biomarkers are increasingly recognized as promising diagnostic and prognostic tools in CRC, and the potential of therapeutic applications aimed at targeting the epigenome is under investigation.

Accuracy of early detection of colorectal tumours by stool methylation markers: A meta-analysis

AIM: To evaluate the accuracy of methylation of genes in stool samples for diagnosing colorectal tumours.

METHODS: Electronic databases including PubMed, Web of Science, Chinese Journals Full-Text Database and Wanfang Journals Full-Text Database were searched to find relevant original articles about methylated genes to be used in diagnosing colorectal tumours. A quality assessment of diagnostic accuracy studies tool (QADAS) was used to evaluate the quality of the included articles, and the Meta-disc 1.4 and SPSS 13.0 software programs were used for data analysis.

RESULTS: Thirty-seven articles met the inclusion criteria, and 4484 patients were included. The sensitivity and specificity for the detection of colorectal cancer (CRC) were 73% (95%CI: 71%-75%) and 92% (95%CI: 90%-93%), respectively. For adenoma, the sensitivity and specificity were 51% (95%CI: 47%-54%) and 92% (95%CI: 90%-93%), respectively. Pooled diagnostic performance of SFRP2 methylation for CRC provided the following results: the sensitivity was 79% (95%CI: 75%-82%), the specificity was 93% (95%CI: 90%-96%), the diagnostic OR was 47.57 (95%CI: 20.08-112.72), the area under the curve was 0.9565. Additionally, the results of accuracy of SFRP2 methylation for detecting colorectal adenomas were as follows: sensitivity was 43% (95%CI: 38%-49%), specificity was 94% (95%CI: 91%-97%), the diagnostic OR was 11.06 (95%CI: 5.77-21.18), and the area under the curve was 0.9563.

CONCLUSION: Stool-based DNA testing may be useful for noninvasively diagnosing colorectal tumours and SFRP2 methylation is a promising marker that has great potential in early CRC diagnosis.

DNA methylation and microRNA biomarkers for noninvasive detection of gastric and colorectal cancer

Cancer initiation and progression is controlled by both genetic and epigenetic events. Epigenetics refers to the study of mechanisms that alter gene expression without permanently altering the DNA sequence. Epigenetic alterations are reversible and heritable, and include changes in histone modifications, DNA methylation, and non-coding RNA-mediated gene silencing. Disruption of epigenetic processes can lead to altered gene function and malignant cellular transformation. Aberrant epigenetic modifications occur at the earliest stages of neoplastic transformation and are now believed to be essential players in cancer initiation and progression. Recent advances in epigenetics have not only offered a deeper understanding of the underlying mechanism(s) of carcinogenesis, but have also allowed identification of clinically relevant putative biomarkers for the early detection, disease monitoring, prognosis and risk assessment of cancer patients. At this moment, DNA methylation and non-coding RNA including with microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) represent the largest body of available literature on epigenetic biomarkers with the highest potential for cancer diagnosis. Following identification of cell-free nucleic acids in systematic circulation, increasing evidence has demonstrated the potential of cell-free epigenetic biomarkers in the blood or other body fluids for cancer detection. In this article, we summarize the current state of knowledge on epigenetic biomarkers - primarily DNA methylation and non-coding RNAs - as potential substrates for cancer detection in gastric and colorectal cancer, the two most frequent cancers within the gastrointestinal tract. We also discuss the obstacles that have limited the routine use of epigenetic biomarkers in the clinical settings and provide our perspective on approaches that might help overcome these hurdles, so that these biomarkers can be readily developed for clinical management of cancer patients.

Colorectal cancer: from prevention to personalized medicine

Colorectal cancer (CRC) is a very heterogeneous disease that is caused by the interaction of genetic and environmental factors. CRC develops through a gradual accumulation of genetic and epigenetic changes, leading to the transformation of normal colonic mucosa into invasive cancer. CRC is one of the most prevalent and incident cancers worldwide, as well as one of the most deadly. Approximately 1235108 people are diagnosed annually with CRC, and 609051 die from CRC annually. The World Health Organization estimates an increase of 77% in the number of newly diagnosed cases of CRC and an increase of 80% in deaths from CRC by 2030. The incidence of CRC can benefit from different strategies depending on its stage: health promotion through health education campaigns (when the disease is not yet present), the implementation of screening programs (for detection of the disease in its early stages), and the development of nearly personalized treatments according to both patient characteristics (age, sex) and the cancer itself (gene expression). Although there are different strategies for screening and although the number of such strategies is increasing due to the potential of emerging technologies in molecular marker application, not all strategies meet the criteria required for screening tests in population programs; the three most accepted tests are the fecal occult blood test (FOBT), colonoscopy and sigmoidoscopy. FOBT is the most used method for CRC screening worldwide and is also the primary choice in most population-based screening programs in Europe. Due to its non-invasive nature and low cost, it is one of the most accepted techniques by population. CRC is a very heterogeneous disease, and with a few exceptions (APC, p53, KRAS), most of the genes involved in CRC are observed in a small percentage of cases. The design of genetic and epigenetic marker panels that are able to provide maximum coverage in the diagnosis of colorectal neoplasia seems a reasonable strategy. In recent years, the use of DNA, RNA and protein markers in different biological samples has been explored as strategies for CRC diagnosis. Although there is not yet sufficient evidence to recommend the analysis of biomarkers such as DNA, RNA or proteins in the blood or stool, it is likely that given the quick progression of technology tools in molecular biology, increasingly sensitive and less expensive, these tools will gradually be employed in clinical practice and will likely be developed in mass.