A new method for isolating colonocytes from naturally evacuated feces and its clinical application to colorectal cancer diagnosis

A simple and effective method to enrich endogenous DNA from mammalian faeces

Utilization of faeces has long been a popular approach for genetic and ecological studies of wildlife. However, the success of molecular marker genotyping and genome resequencing is often unpredictable due to insufficient enrichment of endogenous DNA in the total faecal DNA that is dominated by bacterial DNA. Here, we report a simple and cheap method named PEERS to predominantly lyse animal cells over bacteria by using sodium dodecyl sulphate so as to discharge endogenous DNA into liquid phase before bacterial DNA. By brief centrifugation, total DNA with enriched endogenous fraction can be extracted from the supernatant using routine methods. Our assessments showed that the endogenous DNA extracted by PEERS was significantly enriched for various types of faeces from different species, preservation time and conditions. It significantly improves the genotyping correctness and efficiency of genome resequencing with the total additional cost of $ 0.1 and a short incubation step to treat a faecal sample. We also provide methods to assess the enrichment efficiency of mitochondrial and nuclear DNA and models to predict the usability of faecal DNA for genotyping of short tandem repeat, single-nucleotide polymorphism and whole-genome resequencing.

A new DNA extraction method (HV-CTAB-PCI) for amplification of nuclear markers from open ocean-retrieved faeces of an herbivorous marine mammal, the dugong

Non-invasively collected faecal samples are an alternative source of DNA to tissue samples, that may be used in genetic studies of wildlife when direct sampling of animals is difficult. Although several faecal DNA extraction methods exist, their efficacy varies between species. Previous attempts to amplify mitochondrial DNA (mtDNA) markers from faeces of wild dugongs (Dugong dugon) have met with limited success and nuclear markers (microsatellites) have been unsuccessful. This study aimed to establish a tool for sampling both mtDNA and nuclear DNA (nDNA) from dugong faeces by modifying approaches used in studies of other large herbivores. First, a streamlined, cost-effective DNA extraction method that enabled the amplification of both mitochondrial and nuclear markers from large quantities of dugong faeces was developed. Faecal DNA extracted using a new 'High Volume- Cetyltrimethyl Ammonium Bromide- Phenol-Chloroform-Isoamyl Alcohol' (HV-CTAB-PCI) method was found to achieve comparable amplification results to extraction of DNA from dugong skin. As most prevailing practices advocate sampling from the outer surface of a stool to maximise capture of sloughed intestinal cells, this study compared amplification success of mtDNA between the outer and inner layers of faeces, but no difference in amplification was found. Assessment of the impacts of faecal age or degradation on extraction, however, demonstrated that fresher faeces with shorter duration of environmental (seawater) exposure amplified both markers better than eroded scats. Using the HV-CTAB-PCI method, nuclear markers were successfully amplified for the first time from dugong faeces. The successful amplification of single nucleotide polymorphism (SNP) markers represents a proof-of-concept showing that DNA from dugong faeces can potentially be utilised in population genetic studies. This novel DNA extraction protocol offers a new tool that will facilitate genetic studies of dugongs and other large and cryptic marine herbivores in remote locations.

Colon mucus in colorectal neoplasia and beyond

Little was known about mammalian colon mucus (CM) until the beginning of the 21st century. Since that time considerable progress has been made in basic research addressing CM structure and functions. Human CM is formed by two distinct layers composed of gel-forming glycosylated mucins that are permanently secreted by goblet cells of the colonic epithelium. The inner layer is dense and impenetrable for bacteria, whereas the loose outer layer provides a habitat for abundant commensal microbiota. Mucus barrier integrity is essential for preventing bacterial contact with the mucosal epithelium and maintaining homeostasis in the gut, but it can be impaired by a variety of factors, including CM-damaging switch of commensal bacteria to mucin glycan consumption due to dietary fiber deficiency. It is proven that impairments in CM structure and function can lead to colonic barrier deterioration that opens direct bacterial access to the epithelium. Bacteria-induced damage dysregulates epithelial proliferation and causes mucosal inflammatory responses that may expand to the loosened CM and eventually result in severe disorders, including colitis and neoplastic growth. Recently described formation of bacterial biofilms within the inner CM layer was shown to be associated with both inflammation and cancer. Although obvious gaps in our knowledge of human CM remain, its importance for the pathogenesis of major colorectal diseases, comprising inflammatory bowel disease and colorectal cancer, is already recognized. Continuing progress in CM exploration is likely to result in the development of a range of new useful clinical applications addressing colorectal disease diagnosis, prevention and therapy.

Relation between expression of hMLH1 and p53 mRNA genes, in the feces of patients with colorectal carcinoma. Cross-sectional study

Colorectal carcinoma (CRC) is one of the main public health problems. The mortality of CRC is about 8%. Early detection of CRC is very important to prevent death because this cancer could be cured through surgery if the diagnosis can be made as early as possible. Therefore screening strategy for early detection of CRC is critical in reducing mortality. Many investigations supporting the detection of CRC have been developed, including the fecal DNA mutation test using advanced cytological techniques. It is capable of assessing colonocytes for the presence of DNA, RNA, and protein as molecular biomarkers of neoplasia in CRC, including p53 and hMLH1. This study implemented observational approach with a cross-sectional study of the feces of patients with CRC regardless of the stage and grade. The purpose of this study was to determine the expression of the hMLH1 and p53 mRNA genes in the feces of 48 patients with CRC from two hospitals in Indonesia, Siloam Hospitals in Cikarang and Dr. Wahidin Sudirohusodo Hospital in Makassar. The results showed that all adenocarcinoma feces samples with various tumor stages and grades had excess mRNA expression (more than twice the normal amount in Fold Change units) for both the hMLH1 and p53 genes. The average expression of the hMLH1 mRNA gene was the highest at stage two and grade one, while the lowest was at stage four and grade three. In contrast, the average p53 mRNA gene expression was the highest at stage four and grade three, while the lowest was at stage two and grade one. The study suggested that there was a relation between and the expression of hMLH1 and p53 mRNA gene. We concluded that while both hMLH1 and p53 genes in patients' feces with CRC were overexpressed, they did not significantly affect the grade of CRC.

Coprocytobiology: A Technical Review of Cytological Colorectal Cancer Screening in Fecal Samples

GRAPHICAL ABSTRACT

Identifying Novel Biomarkers Ready for Evaluation in Low-Prevalence Populations for the Early Detection of Lower Gastrointestinal Cancers: A Systematic Review and Meta-Analysis

INTRODUCTION

Lower gastrointestinal (GI) cancers are a major cause of cancer deaths worldwide. Prognosis improves with earlier diagnosis, and non-invasive biomarkers have the potential to aid with early detection. Substantial investment has been made into the development of biomarkers; however, studies are often carried out in specialist settings and few have been evaluated for low-prevalence populations.

METHODS

We aimed to identify novel biomarkers for the detection of lower GI cancers that have the potential to be evaluated for use in primary care. MEDLINE, Embase, Emcare and Web of Science were systematically searched for studies published in English from January 2000 to October 2019. Reference lists of included studies were also assessed. Studies had to report on measures of diagnostic performance for biomarkers (single or in panels) used to detect colorectal or anal cancers. We included all designs and excluded studies with fewer than 50 cases/controls. Data were extracted from published studies on types of biomarkers, populations and outcomes. Narrative synthesis was used, and measures of specificity and sensitivity were meta-analysed where possible.

RESULTS

We identified 142 studies reporting on biomarkers for lower GI cancers, for 24,844 cases and 45,374 controls. A total of 378 unique biomarkers were identified. Heterogeneity of study design, population type and sample source precluded meta-analysis for all markers except methylated septin 9 (mSEPT9) and pyruvate kinase type tumour M2 (TuM2-PK). The estimated sensitivity and specificity of mSEPT9 was 80.6% (95% CI 76.6-84.0%) and 88.0% (95% CI 79.1-93.4%) respectively; TuM2-PK had an estimated sensitivity of 81.6% (95% CI 75.2-86.6%) and specificity of 80.1% (95% CI 76.7-83.0%).

CONCLUSION

Two novel biomarkers (mSEPT9 and TuM2-PK) were identified from the literature with potential for use in lower-prevalence populations. Further research is needed to validate these biomarkers in primary care for screening and assessment of symptomatic patients.

Upregulation of Fecal Epithelial Heparanase mRNA Is Associated with Increased Ulcerative Colitis Activity and Cancerization Risk

BACKGROUND

Heparanase (HPSE) is considered to play an important role in the occurrence, development and carcinogenesis of ulcerative colitis (UC). There are no reports about the detection of HPSE mRNA in feces to predict UC activity and cancerization risk.

AIMS

To explore the feasibility and effectiveness of fecal epithelial HPSE mRNA in monitoring patients' UC activity and predicting cancer risk.

METHODS

The clinical part of the study enrolled 20 patients with UC and 20 controls. Meanwhile, a UC-induced carcinogenesis mouse model was established using a combination treatment of dimethylhydrazine and dextran sulfate sodium. Tissue expression of HPSE protein was detected by immunohistochemistry. RT-qPCR was used to detect the expression of HPSE mRNA in colonic mucosa and feces.

RESULTS

In the human study, the relative expressions of HPSE mRNA in colonic mucosa and feces were positively correlated with the Mayo score (P < 0.05), and with a significant correlation between feces and colonic mucosa (P < 0.05). In the mouse model, the relative expressions of HPSE mRNA in colonic mucosa and feces in the ulcerative colitis-associated colorectal cancer group was significantly higher than that of the UC group and the normal control group (P < 0.05), and with a significant correlation between feces and colonic mucosa (P < 0.05).

CONCLUSIONS

The relative level of HPSE mRNA was positively correlated with UC activity and cancerization. The relative level of HPSE mRNA in feces was correlated with that in colonic mucosa. The detection of HPSE mRNA in feces can be used as a new marker for disease monitoring and cancer risk prediction of UC.

Endoplasmic reticulum stress occurs in association with the extrusion of toxic extracellular vesicles from human placentae treated with antiphospholipid antibodies

Antiphospholipid autoantibodies (aPLs), a major maternal risk factor for preeclampsia, are taken into the syncytiotrophoblast where they bind intracellular vesicles and mitochondria. Subsequently, large quantities of extracellular vesicles (EVs) extruded from syncytiotrophoblast into the maternal circulation are altered such that they cause maternal endothelial cell activation. However, the mechanism driving this change is unknown. First trimester placental explants were treated with aPL for 18 h. The EVs were then collected by different centrifugation. The levels of HSP 70, misfolded proteins, caspase 8 activity, and Mixed Lineage Kinase domain-Like (MLKL) were measured in placental explants and EVs. In addition, the levels of TNF-α and CD95 in conditioned medium were also measured. Treating placental explants with aPL caused an increase in levels of HSP 70, misfolded proteins and MLKL in placental explants and EVs. Increased activity of caspase 8 was also seen in placental explants. Higher levels of TNF-α were seen conditioned medium from aPL-treated placental explant cultures. aPLs appear to induce endoplasmic reticulum stress in the syncytiotrophoblast in a manner that involved caspase 8 and TNF-α. To avoid accumulation of the associated misfolded proteins and MLKL, the syncytiotrophoblast exports these potentially dangerous proteins in EVs. It is likely that the dangerous proteins that are loaded into placental EVs in preeclampsia contribute to dysfunction of the maternal cells.

Identification and Validation of MicroRNA Profiles in Fecal Samples for Detection of Colorectal Cancer

BACKGROUND & AIMS

Screening for colorectal cancer (CRC) is effective in the population at average risk. The most extended strategy in organized programs involves the fecal immunochemical test, which is limited by low sensitivity for the detection of advanced adenomas (AAs). We aimed to identify microRNA (miRNA) signatures in fecal samples that identify patients with AAs or CRC and might be used in noninvasive screening.

METHODS

Our study comprised 4 stages. In the discovery phase, we performed genome-wide miRNA expression profiling of 124 fresh, paired colorectal tumor and nontumor samples (30 CRC; 32 AAs) from patients in Spain. In the technical validation stage, miRNAs with altered expression levels in tumor vs nontumor tissues were quantified by reverse-transcription polymerase chain reaction in fecal samples from a subset of patients included in the discovery phase (n = 39) and individuals without colorectal neoplasms (controls, n = 39). In the clinical validation stage, the miRNAs found to be most significantly up-regulated by quantitative reverse transcription polymerase chain reaction analysis were measured in an independent set of fecal samples (n = 767) from patients with positive results from fecal immunochemical tests in a CRC screening program. Finally, we developed a model to identify patients with advanced neoplasms (CRCs or AAs) based on their miRNA profiles, using findings from colonoscopy as the reference standard.

RESULTS

Among 200 and 324 miRNAs significantly deregulated in CRC and AA tissues, respectively, 7 and 5 of these miRNAs were also found to be deregulated in feces (technical validation). Of them, MIR421, MIR130b-3p, and MIR27a-3p were confirmed to be upregulated in fecal samples from patients with advanced neoplasms. In our model, the combination of fecal level of MIR421, MIR27a-3p, and hemoglobin identified patients with CRC with an area under the curve (AUC) of 0.93, compared with an AUC of 0.67 for fecal hemoglobin concentration alone.

CONCLUSIONS

We found that increased levels of 2 miRNAs and hemoglobin in feces can identify patients with AAs or CRC more accurately than fecal hemoglobin concentration alone. Assays for these miRNAs might be added to fecal tests for the detection of CRC or AAs.

Circulating biomarkers for early detection and clinical management of colorectal cancer

New non-invasive approaches that can complement and improve on current strategies for colorectal cancer (CRC) screening and management are urgently needed. A growing number of publications have documented that components of tumors, which are shed into the circulation, can be detected in the form of liquid biopsies and can be used to detect CRC at early stages, to predict response to certain therapies and to detect CRC recurrence in a minimally invasive way. The analysis of circulating tumor DNA (ctDNA), tumor-derived cells (CTC, circulating tumor cells) or circulating microRNA (miRNA) in blood and other body fluids, have a great potential to improve different aspects of CRC management. The challenge now is to find which types of components, biofluids and detection methods would be the most suitable to be applied in the different steps of CRC detection and treatment. This chapter will provide an up to date review on ctDNA, CTCs and circulating miRNAs as new biomarkers for CRC, either for clinical management or early detection, highlighting their advantages and limitations.

RT-qPCR for Fecal Mature MicroRNA Quantification and Validation

By routinely and systematically being able to perform quantitative stem-loop reverse transcriptase (RT) followed by TaqMan® minor-groove binding (MGB) probe, real-time quantitative PCR analysis on exfoliated enriched colonocytes in stool, using human (Homo sapiens, hsa) micro(mi)RNAs to monitor changes of their expression at various stages of colorectal (CRC) progression, this method allows for the reliable and quantitative diagnostic screening of colon cancer (CC). Although the expression of some miRNA genes tested in tissue shows less variability in normal or cancerous patients than in stool, the noninvasive stool by itself is well suited for CC screening. An miRNA approach using stool promises to offer more sensitivity and specificity than currently used genomic, methylomic, or proteomic methods for CC screening.To present an application of employing miRNAs as diagnostic markers for CC screening, we carried out global microarray expression studies on stool colonocytes isolated by paramagnetic beads, using Affymetrix GeneChip miRNA 3.0 Array, to select a panel of miRNAs for subsequent focused semiquantitative PCR analysis studies. We then conducted a stem-loop RT-TaqMan® MGB probes, followed by a modified real-time qPCR expression study on 20 selected miRNAs for subsequent validation of the extracted immunocaptured total small RNA isolated from stool colonocytes. Results showed 12 miRNAs (miR-7, miR-17, miR-20a, miR-21, miR-92a, miR-96, miR-106a, miR-134, miR-183, miR-196a, miR-199a-3p, and miR214) to have an increased expression in stool of CC patients, and that later TNM stages exhibited more increased expressions than adenomas, while 8 miRNAs (miR-9, miR-29b, miR-127-5p, miR-138, miR-143, miR-146a, miR-222, and miR-938) showed decreased expressions in stool of CC patients, which becomes more pronounced as the cancer progresses from early to late TNM stages (0-IV).

Molecular biomarkers for an early diagnosis, effective treatment and prognosis of colorectal cancer: Current updates

Colorectal cancer (CRC) is the third most prevalent cancer in the world. Globally, it has been estimated that about 1.4 million new cases of colorectal cancer are diagnosed every year. CRC is a multifactorial disease that arises due to genetics as well as epigenetic alterations in a number of oncogenes, tumor suppressor genes, mismatch repair genes, as well as cell cycle regulating genes in colon mucosal cells. These molecular alterations have been considered as potential CRC biomarkers because they can provide the physicians with diagnostic, prognostic and treatment response information. The goal is to identify relevant, cheap and applicable biomarkers that contribute to patient management decisions, resulting in direct benefits to patients. In this review, we will outline the most currently available and developing tumor tools, and blood molecular biomarkers. Also, we will illustrate their diagnostic, therapeutic and prognostic applications.

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.

Assessment of cytology and mucin 2 in colorectal mucus collected from patients with inflammatory bowel disease: Results of a pilot trial

BACKGROUND AND AIM

Non-invasive diagnosis of colorectal disease remains problematic, fecal biomarkers presenting the only current option. Colorectal mucus is the diagnostically informative element of stool samples, but its separation from stool is difficult. We aimed to: (i) test a novel method of non-invasive colorectal mucus sampling in a pilot clinical trial; (ii) evaluate sampling method acceptance by study participants; (iii) characterize the collected material cytologically; and (iv) assess feasibility of quantitative protein analysis in the samples.

METHODS

A total of 141 patients with IBD (58), IBS (50), and healthy controls (33) participated in the study. Samples rich in colorectal mucus were self-collected by swabbing the anal area immediately following defecation. Collected samples were examined cytologically and subjected to quantitative analysis for total protein and mucin 2 (MUC2).

RESULTS

The novel sampling technique was assessed as "good" or "adequate" by 96% of study participants. A total of 55% of the collected samples were free of fecal contamination. Cytology showed large numbers of well preserved inflammatory cells in IBD cases. Total protein values varied in all groups, being affected by fecal contamination. MUC2 levels were similar among all IBD-free individuals (control and IBS groups) and elevated in IBD patients (p < 0.001). MUC2 measurement applied as a test for IBD detection provided sensitivity = 72.4% and specificity = 86.7%.

CONCLUSIONS

A novel non-invasive method for collecting human colorectal mucus has been successfully tested. The method was very well accepted by trial participants. The results have proven high quality of collected samples for both cytological investigation and diagnostic biomarker analysis.

Colorectal mucus non-invasively collected from patients with inflammatory bowel disease and its suitability for diagnostic cytology

Colorectal mucus is a key component of the protective gut barrier which is altered in inflammatory bowel disease (IBD). We aimed to cytologically characterize colorectal mucus non-invasively collected from IBD patients using our new sampling technique. Colorectal mucus was self-collected by 58 IBD patients comprising 31 ulcerative colitis (UC) and 27 Crohn's disease (CD) cases. The samples were examined cytologically, and immunocytochemically. Large numbers of well-preserved granulocytes were typically detected (neutrophils undergoing degradation were observed as well). Plasma cells and erythrophagocytosis were present in 18.2% and 29.1% of cases, respectively, predominantly in patients with UC and distal CD. Immunocytochemical visualization of calprotectin in neutrophils, eosinophil-derived neurotoxin in eosinophils and tumour necrosis factor-α in macrophages was also achieved. Correct cytological diagnosis was made in 61.8% of analysed IBD cases. Our new method of colorectal mucus sampling provides highly informative material for cytology. Findings of the presence of plasmocytes and erythrophagocytosis in colorectal mucus are unique and may reflect previously unknown mechanisms of IBD pathogenesis. Immunocytochemical detection of inflammation biomarkers demonstrates the suitability of this material for biomarker quantification. These promising results suggest a potential role for colorectal mucus cytology in the non-invasive diagnosis of IBD.

miRNA as markers for the diagnostic screening of colon cancer

Early screening for colon cancer (CC) allows for early stage diagnosis of the malignancy and potentially reduces disease mortality as the cancer is most likely curable at its earliest stages. Early detection would be desirable if accurate, practical and cost-effective diagnostic measures for this cancer were available. Mortality and morbidity from CC represent a major health problem involving a malignant disease that is theoretically preventable through screening. Current screening methods (e.g., the convenient and inexpensive immunological fecal occult blood test, FOBTi, obtained from patients' medical records) either lack sensitivity and require dietary restriction, which impedes compliance and use; are costly (e.g., colonoscopy), which decreases compliance; or could result in mortality. In comparison with the FOBT test, a non-invasive sensitive screen for which there is no requirement for dietary restriction would be a more convenient test. Colorectal cancer is the only cancer for which colonoscopy is recommended as a screening method. Although colonoscopy is a reliable screening tool, the invasive nature, abdominal pain, potential complications and high cost have hampered the application of this procedure worldwide. A screening approach using the stable miRNA molecules, which are relatively non-degradable when extracted from non-invasive stool and semi-invasive blood samples by commercially available kits and manipulated thereafter, would be preferable to a transcriptomic mRNA-, a mutation DNA-, an epigenetic- or a proteomic-based test. The approach uses reverse transcriptase, modified real-time quantitative PCR. Although exosomal RNA would be missed, using a restricted extraction of total RNA from stool or blood, a parallel test could also be carried out on RNA obtained from stool or plasma samples, and appropriate corrections for exsosomal loss can be made for accurate and quantitative test result. Eventually, a chip can be developed to facilitate diagnosis, as has been done for the quantification of genetically modified organisms in foods. The gold standard to which the molecular miRNA test is compared is colonoscopy, which can be obtained from patients' medical records. If performance criteria are met, as detailed herein, a miRNA test in human stool or blood samples based on high-throughput automated technologies and quantitative expression measurements commonly used in the diagnostic clinical laboratory should be advanced to the clinical setting, which will make a significant impact on CC prevention.

Probiotics and prebiotics in neonatal necrotizing enterocolitis: New opportunities for translational research

Neonatal necrotizing enterocolitis (NEC) in premature infants has been recognized as a defined disease entity for at least four decades. Although survival has increased due to the advent of more sophisticated intensive care, incidence and long term health impacts due to NEC remain unchanged and no preventive therapy is currently available. Different probiotic strains of bacteria have been examined in their ability to prevent NEC with varied but encouraging results. Undigestable prebiotic sugars known to promote the growth of probiotic bacteria in the colon have been used in neonates with no clear benefit. The literature on NEC and probiotics is now cluttered with more reviews and meta-analyses than number of clinical trials. On the other hand, significant new information is available on microbiota and their impact on gut immunity. This review attempts to reiterate the risk factors of NEC and the pathogenesis of NEC with special reference to gut permeability. The reader is then introduced to gut microbiota, uniqueness and differences among probiotic strains, and how multiple resident flora talk to each other in the community setting in the human gut. After presenting a concise review of available clinical research results, the reader is challenged to question as to why no precise answer is available at present. Some modalities to examine the complex microflora and changes in the neonatal gut are then proposed including non-invasive methods and mathematical modeling. The review concludes by attracting the reader's attention to known immunomodulators of inflammation and injury. Justice to this review will be done only if the readers, clinical, and basic science investigators from multiple fields gather courage for a paradigm shift and embark on understanding the pathophysiology of the disease and attempt to discern the difference from equally preterm, equally vulnerable neonates that do not develop NEC. Learning about the developing microbiota in neonatal gut and its immunological impacts on the host in the face of many variables will provide a leap in our pursuit to select better, if not the best candidate probiotics, and put them to work against this stubborn disease that continues to take a toll on our precious neonates and the society.

New molecular diagnosis and screening methods for colorectal cancer using fecal protein, DNA and RNA

Several screening methods for reducing the mortality rate of colorectal cancer (CRC) have been reported in recent decades. Fecal occult blood tests (FOBTs) are widely used for CRC screening and immunochemical FOBTs perform better than guaiac FOBTs; however, the sensitivity and specificity of immunochemical FOBTs remain unsatisfactory. To resolve this problem, novel fecal molecular methods based on fecal protein, DNA and RNA analyses have been developed. Regarding fecal proteins, several marker proteins indicating intestinal bleeding and cancer cell-specific proteins have been investigated. Regarding fecal DNA, numerous gene mutation and gene methylation analyses have been reported. Consequently, fecal DNA analysis was recommended as a CRC screening method in 2008. In addition, gene expression analyses of CRC-specific genes and miRNAs in fecal RNA have been investigated over the last decade. This review article summarizes molecular methods using fecal samples for CRC screening, focusing on reports within the last 5 years.

Fecal Collection and Stabilization Methods for Improved Fecal DNA Test for Colorectal Cancer in a Screening Setting

Early detection of CRC and adenomas reduces CRC-related mortality. The optimal screening test for CRC is still a subject of debate, and molecular stool sample analysis could provide a valid alternative to conventional methods in terms of compliance and practicability. Seven fecal DNA storage systems were evaluated in two successive phases. In the first phase of the study was selected the preservative buffer able to ensure the best human DNA recovery. In the second phase was evaluated human DNA stability, amplificability and integrity in DNA extracted from selected buffer. Results showed that the best performance was obtained in samples stored in 100 mM EDTA buffer and Genefec buffer. Likewise buffer addition yielded a significant increase in DNA stability and integrity without PCR inhibition, compared to the matched aliquots with no buffer added. Our study shows that samples collected in stabilization solution stabilize DNA so that intact nucleic acids, are more effectively detectable in the molecular assay. DNA buffer preservation and storage conditions could be useful to guarantee the most consistent yield in human DNA. Stabilization buffer addition to stool samples prior to transport presents an easily implemented solution that appears to be highly effective. Overall DNA extracted from faeces preserved in preservative buffer can feasibility been used for molecular analysis leading to an increase of assay sensitivity.

Diagnostic value of stool DNA testing for multiple markers of colorectal cancer and advanced adenoma: a meta-analysis

BACKGROUND AND OBJECTIVES

The diagnostic value of stool DNA (sDNA) testing for colorectal neoplasms remains controversial. To compensate for the lack of large-scale unbiased population studies, a meta-analysis was performed to evaluate the diagnostic value of sDNA testing for multiple markers of colorectal cancer (CRC) and advanced adenoma.

METHODS

The PubMed, Science Direct, Biosis Review, Cochrane Library and Embase databases were systematically searched in January 2012 without time restriction. Meta-analysis was performed using a random-effects model using sensitivity, specificity, diagnostic OR (DOR), summary ROC curves, area under the curve (AUC), and 95% CIs as effect measures. Heterogeneity was measured using the χ(2) test and Q statistic; subgroup analysis was also conducted.

RESULTS

A total of 20 studies comprising 5876 individuals were eligible. There was no heterogeneity for CRC, but adenoma and advanced adenoma harboured considerable heterogeneity influenced by risk classification and various detection markers. Stratification analysis according to risk classification showed that multiple markers had a high DOR for the high-risk subgroups of both CRC (sensitivity 0.759 [95% CI 0.711 to 0.804]; specificity 0.883 [95% CI 0.846 to 0.913]; AUC 0.906) and advanced adenoma (sensitivity 0.683 [95% CI 0.584 to 0.771]; specificity 0.918 [95% CI 0.866 to 0.954]; AUC 0.946) but not for the average-risk subgroups of either. In the methylation subgroup, sDNA testing had significantly higher DOR for CRC (sensitivity 0.753 [95% CI 0.685 to 0.812]; specificity 0.913 [95% CI 0.860 to 0.950]; AUC 0.918) and advanced adenoma (sensitivity 0.623 [95% CI 0.527 to 0.712]; specificity 0.926 [95% CI 0.882 to 0.958]; AUC 0.910) compared with the mutation subgroup. There was no significant heterogeneity among studies for subgroup analysis.

CONCLUSION

sDNA testing for multiple markers had strong diagnostic significance for CRC and advanced adenoma in high-risk subjects. Methylation makers had more diagnostic value than mutation markers.

Fecal miR-106a is a useful marker for colorectal cancer patients with false-negative results in immunochemical fecal occult blood test

BACKGROUND

Immunochemical fecal occult blood test (iFOBT) is widely used for colorectal cancer screening; however, its sensitivity is insufficient. We recently reported a fecal microRNA (miRNA) test (FmiRT) to detect colorectal cancer. In this study, we investigated a new colorectal cancer screening method combining iFOBT and FmiRT to improve the sensitivity compared with iFOBT alone.

METHODS

In total, 117 colorectal cancer patients and 107 healthy volunteers were enrolled. Ten-milligram fecal samples were collected and iFOBT was conducted. Fecal RNA was extracted from residuum of iFOBT and then the expression of 14 kinds of miRNA was analyzed for the FmiRT using real-time reverse transcription PCR.

RESULTS

Levels of fecal miR-106a expression in iFOBT+ patients and iFOBT- patients were significantly higher than in healthy volunteers (P = 0.001). The sensitivity and specificity of FmiRT using miR-106a were 34.2% and 97.2%, and those of iFOBT were 60.7% and 98.1%, respectively. The overall sensitivity and specificity of the new screening method combining iFOBT and FmiRT were 70.9% and 96.3%, respectively. One quarter of colorectal cancer patients with false-negative iFOBT seemed to be true positive upon adding FmiRT using fecal miR-106a.

CONCLUSIONS

Fecal miR-106a is a good molecular marker to identify colorectal cancer patients from among those with negative iFOBT results. FmiRT combined with iFOBT may improve the sensitivity to detect colorectal cancer.

IMPACT

We have shown the usefulness of fecal miR-106a to detect the colorectal cancer patients among those with negative iFOBT results.

Application of the fecal microRNA test to the residuum from the fecal occult blood test

OBJECTIVE

Though the fecal occult blood test is used for colorectal cancer screening worldwide, it does not have a particularly high sensitivity for detecting colorectal cancer. Here we investigated the applicability of the fecal microRNA test to fecal samples that had been used for a previous fecal occult blood test and stored under various conditions.

METHODS

Five colorectal cancer patients and five healthy volunteers were enrolled. Fecal samples were stored for 0-5 days at 4°C, room temperature or 37°C. Total RNA was extracted from the fecal occult blood test residuum and microRNA expression was analyzed by real-time reverse transcription polymerase chain reaction.

RESULTS

There were no remarkable differences either in colorectal cancer patients or in controls with regard to the concentration of RNA extracted from the fecal occult blood test residuum in any of the storage groups compared with the samples prepared on day 0 (Group 0). Ribosomal RNA stored at room temperature or 37°C degraded rapidly. In contrast, the ribosomal RNA stored at 4°C remained intact for at least 5 days. The microRNAs in samples stored at 4°C and room temperature were conserved; however, the microRNAs stored at 37°C were significantly degraded compared with Group 0 (P < 0.05). In the residuum stored at 4°C up to 5 days, the relative quantification of miR-106a normalized with miR-24 in colorectal cancer patients was significantly higher than those in healthy volunteers (P < 0.05). In contrast, the quantification of normalized miR-106a was remarkably low in samples stored at room temperature and 37°C.

CONCLUSIONS

Fecal microRNA of sufficient quality for reverse transcription polymerase chain reaction analysis was extracted from the fecal occult blood test residuum stored at 4°C for up to 5 days.

Noninvasive screening tests for colorectal cancer

BACKGROUND

Identifying an accurate, reliable, affordable, and acceptable noninvasive screening test for colorectal cancer (CRC) would greatly facilitate population screening.

METHODS

Published literature from 2000 through February 2012 on noninvasive CRC screening tests was identified, reviewed, and summarized.

RESULTS

The highest quality evidence for noninvasive screening exists for guaiac-based fecal occult blood tests (gFOBTs), for which the CRC-specific incidence and mortality reductions are modest. Fecal immunochemical tests (FITs) offer better sensitivity and comparable specificity. Cross-sectional studies comparing gFOBTs and FITs suggest that FITs provide higher detection of advanced neoplasia. Modeling studies favor FITs over gFOBTs with respect to effectiveness and cost-effectiveness. A myriad of studies report the performance of fecal-based and blood-based genetic and protein-based biomarkers; the studies differ in patient population assembled, marker selection, and assay methods. Several markers and panels of markers are promising, although nearly all studies focus on new markers and/or assay methods on small sets of referred patients rather than validating markers using optimal assays in a screening setting.

CONCLUSION

In the absence of long-term randomized trials, adoption of the noninvasive tests will require cross-sectional data on test characteristics obtained from the screening setting, where CRC prevalence is low and the full spectrum of colorectal findings exists, along with estimates of cumulative risks, benefits, and cost-effectiveness. Test adoption will ultimately depend on test characteristics, availability, affordability, and user appeal. There is no noninvasive substitute for the currently recommended screening tests. FITs should replace gFOBTs wherever gFOBTs are used for screening.

Exosome can prevent RNase from degrading microRNA in feces

BACKGROUND

Because the stability of miRNA in feces has not been clarified, we examined the stability of miRNA in feces.

METHODS

RNase was added into culture media of HT-29 cells and fecal homogenates. The relative quantifications of miRNA were analyzed by real-time RT-PCR.

RESULTS

Cellular miRNA or exosomal miRNA were protected from RNase by the cellular membrane or the exosome; meanwhile, free miRNA was degraded immediately and completely by RNase.

CONCLUSION

The present study revealed that exosome or cellular membrane could prevent RNase from degrading miRNA inside the exosome or cells even in a dreadful condition, as in feces.

Use of RNA isolated from feces as a promising tool for the early detection of colorectal cancer

Colorectal cancer is one of the most common forms of cancer worldwide. Early detection would allow patients to be treated surgically and halt the progression of the disease; however, the current methods of early detection are invasive (colonoscopy and sigmoidoscopy) or have low sensitivity (fecal occult blood test). The altered expression of genes in stool samples of patients with colorectal cancer can be determined by RT-PCR. This is a noninvasive and highly sensitive technique for colorectal cancer screening. According to information gathered in this review and our own experience, the use of fecal RNA to determine early alterations in gene expression due to malignancy appears to be a promising alternative to the current detection methods and owing to its low cost could be implemented in public health services.

Fecal molecular markers for colorectal cancer screening

Despite multiple screening techniques, including colonoscopy, flexible sigmoidoscopy, radiological imaging, and fecal occult blood testing, colorectal cancer remains a leading cause of death. As these techniques improve, their sensitivity to detect malignant lesions is increasing; however, detection of precursor lesions remains problematic and has generated a lack of general acceptance for their widespread usage. Early detection by an accurate, noninvasive, cost-effective, simple-to-use screening technique is central to decreasing the incidence and mortality of this disease. Recent advances in the development of molecular markers in faecal specimens are encouraging for its use as a screening tool. Genetic mutations and epigenetic alterations that result from the carcinogenetic process can be detected by coprocytobiology in the colonocytes exfoliated from the lesion into the fecal matter. These markers have shown promising sensitivity and specificity in the detection of both malignant and premalignant lesions and are gaining popularity as a noninvasive technique that is representative of the entire colon. In this paper, we summarize the genetic and epigenetic fecal molecular markers that have been identified as potential targets in the screening of colorectal cancer.

Molecular tests for colorectal cancer screening

Detecting and removing high-risk adenomas and early colorectal cancer (CRC) can reduce mortality of this disease. The noninvasive fecal occult blood test (FOBT; guaiac-based or immunochemical) is widely used in screening programs and although effective, it leaves room for improvement in terms of test accuracy. Molecular tests are expected to be more sensitive, specific and informative than current detection tests, and are promising future tools for CRC screening. This review provides an overview of the performances of DNA, RNA, and protein markers for CRC detection in stool and blood. Most emphasis currently is on DNA and protein markers. Among DNA markers there is trend to move away from mutation markers in favor of methylation markers. The recent boost in proteomics research leads to many new candidate protein markers. Usually in small series, some markers show better performance than the present FOBT. Evaluation in large well-controlled randomized trials is the next step needed to take molecular markers for CRC screening to the next level and warrant implementation in a screening setting.

Live colonocytes in newborn stool: surrogates for evaluation of gut physiology and disease pathogenesis

Studies of gastrointestinal pathophysiology are not feasible by biopsies in human neonates. We examined the utility of live colonocytes in stool in studying cellular markers during early neonatal life. Expression of IgA, IgG, cluster of differentiation-45 cells (CD45), and toll-like receptors-2 and 4 (TLR2 and TLR4) were analyzed by flow cytometry. Colonocyte RNA extracts were used in quantitative real-time PCR (qRT-PCR) to examine the expression of cytokeratin-19, ribosomal protein-24, and tight-junction (Tj) protein zonula occludens-1 (ZO-1). Colonocyte yield varied between 5 × 10⁴ to 2 × 10⁶ cells/g of stool. Meconium samples yielded a highly enriched population of viable cells. Although low, all samples showed CD45-positive cells during the initial weeks of life. Starting as early as d 2, IgA expression was observed in 69% of the cells. Low to moderate expression of IgG was observed with a linear increase as the infants grew. There was an almost total lack of TLR2 staining; however, >55% of the colonocytes showed TLR4 expression. Although high levels of IgA in gut cells may serve as a natural protectant during neonatal period, increased TLR4 may provide a niche for lipopolysaccharide (LPS)-mediated epithelial damage. Use of stool colonocytes can be a valuable noninvasive approach for studying gut pathophysiology in the neonatal period.

Digital analysis of the expression levels of multiple colorectal cancer-related genes by multiplexed digital-PCR coupled with hydrogel bead-array

To digitally analyze expression levels of multiple genes in one reaction, we proposed a method termed as 'MDHB' (Multiplexed Digital-PCR coupled with Hydrogel Bead-array). The template for bead-based emulsion PCR (emPCR) was prepared by reverse transcription using sequence-tagged primers. The beads recovered from emPCR were immobilized with hydrogel to form a single-bead layer on a chip, and then decoded by gene-specific probe hybridization and Cy3-dUTP based primer extension reaction. The specificity of probe hybridization was improved by using electrophoresis to remove mismatched probes on the bead's surface. The number of positive beads reflects the abundance of expressed genes; the expression levels of target genes were normalized to a housekeeping gene and expressed as the number ratio of green beads to red beads. The discrimination limit of MDHB is 0.1% (i.e., one target molecule from 1000 background molecules), and the sensitivity of the method is below 100 cells when using the β-actin gene as the detection target. We have successfully employed MDHB to detect the relative expression levels of four colorectal cancer (CRC)-related genes (c-myc, COX-2, MMP7, and DPEP1) in 8 tissue samples and 9 stool samples from CRC patients, giving the detection rates of 100% and 77%, respectively. The results suggest that MDHB could be a potential tool for early non-invasive diagnosis of CRC.

MicroRNA expression profiling of exfoliated colonocytes isolated from feces for colorectal cancer screening

To reduce the colorectal cancer (CRC) mortality rate, we have reported several CRC screening methods using colonocytes isolated from feces. Expression analysis of oncogenic microRNA (miRNA) in peripheral blood was recently reported for CRC detection. In the present study, we conducted miRNA expression analysis of exfoliated colonocytes isolated from feces for CRC screening. Two hundred six CRC patients and 134 healthy volunteers were enrolled in the study. miRNA expression of the miR-17-92 cluster, miR-21, and miR-135 in colonocytes isolated from feces as well as frozen tissues was analyzed by quantitative real-time PCR. The expression of the miR-17-92 cluster, miR-21, and miR-135 was significantly higher in CRC tissues compared with normal tissues. The exfoliated colonocytes of 197 CRC patients and 119 healthy volunteers were analyzed because of the presence of sufficient miRNA concentration. miR-21 expression did not differ significantly between CRC patients and healthy volunteers (P = 0.6). The expression of miR-17-92 cluster and miR-135 was significantly higher in CRC patients than in healthy volunteers (P < 0.0001). The overall sensitivity and specificity by using miRNA expression was 74.1% (146/197; 95% confidence interval, 67.4-80.1) and 79.0% (94/119; 95% confidence interval, 70.6-85.9), respectively. Sensitivity was dependent only on tumor location (P = 0.0001). miRNA was relatively well conserved in exfoliated colonocytes from feces both of CRC patients and healthy volunteers. miRNA expression analysis of the isolated colonocytes may be a useful method for CRC screening. Furthermore, oncogenic miRNA highly expressed in CRC should be investigated for CRC screening tests in the future.

[Advances in early diagnosis of colorectal cancer based on detection of RNAs in stool.]

Colorectal cancer (CRC) is one of the most malignant cancers in gastrointestinal tract. In China, there are increasing rates of morbidity and mortality for CRC. As the mortality is closely related to the stage of disease at time of diagnosis, early diagnosis of CRC is important. However, current techniques used for clinical diagnosis have limitations which made them difficult to achieve the early diagnosis. The detection of RNAs in stool is a newly developed noninvasive technique for early diagnosis of CRC at molecular levels. Compared with the techniques including colonoscopy, fecal occult-blood test and stool DNA-based mutation detection, diagnosis based on the detection of RNAs in stool has the advantages of low-cost and high sensitivity. Moreover, stool RNA-based techniques are able to analyze multiplexed gene expression simultaneously and monitor cancer progression dynamically. This paper introduced the feasibility of stool RNA analysis, and systematically reviewed the genes associated with stool RNA analysis, methods of RNA isolation from stool sample, and techniques for gene expression analysis in stool RNA. Finally, further applications of stool RNA-based techniques for early diagnosis of CRC were briefly discussed.

Can DNA sampling from the rectal mucosa be a novel tool for the detection of colorectal cancer?

INTRODUCTION

The objective was to evaluate a new method for DNA sampling from the rectal mucosa for the detection of colorectal cancer or any clinically significant pathology in the colon and rectum.

METHODS

This prospective cohort study included patients scheduled for colonoscopy (group 1, n = 185) or colonic resection because of suspected colorectal cancer (group 2, n = 62). A test instrument with a balloon-holding end was introduced through a proctoscope into the rectum to collect exfoliated cells, from which DNA was isolated and quantified.

RESULTS

The detection of colorectal cancer in group 1 showed a sensitivity for the DNA cut-off levels 1.5, 2, and 2.5 microg/ml of 100%, 80%, and 60%, and a specificity of 37%, 46%, and 56%, respectively. In group 2, for the same cut-off levels, the sensitivity was 73%, 61%, and 55%, and the specificity was 67%, 67%, and 67%, respectively.

CONCLUSIONS

This novel technique is a safe and easy way of collecting DNA from the rectal mucosa. The sensitivity and specificity of the test were too low to be acceptable for a screening test. The low sensitivity and specificity in this study could be explained by the diversity within the study groups as many patients presented with long-term history of colorectal disease and surgical interventions in the past.

Isolation of stool-derived mucus provides a high yield of colonocytes suitable for early detection of colorectal carcinoma

BACKGROUND

Promising stool-based screening tests for colorectal carcinoma (CRC) rely on detection of exfoliated colonocytes or their contents. However, methods of colonocyte retrieval have not been studied systematically and current approaches are restricted by low yields. We examined colonocyte numbers in stool wash fractions and assessed the suitability of retrieved cells for immunocytochemistry for minichromosome maintenance protein 2 (MCM2), a marker of the proliferative deregulation that characterizes malignancy.

METHODS

Colonocyte numbers were accurately quantified in 129 wash fractions derived from 18 stools, comparing the mucus retained by a 125-microm filter (F fraction) with the fine and coarse content in the filtrate (S and P fractions, respectively). MCM2 immunocytochemistry was done on sections of fibrin clot containing filter-derived mucus, obtained from stools of eight independent subjects.

RESULTS

Total colonocyte yield in the F fraction (mean, 433.8 per 100 microL) was higher than in the S (140.3) and P (204.6) fractions (P = 0.004 and 0.03, respectively) due to increased numbers of morphologically abnormal cells, which predominantly represented malignant cells in samples from CRC patients. Several thousand abnormal cells could be obtained from stool-derived mucus in all CRC patients, an order of magnitude greater than numbers in subjects without CRC. Median MCM2 labeling index in abnormal cells was 50% (range, 30-60%) in CRC patients and 0% in subjects without CRC. Cells in clot sections were well preserved and not obscured by fecal debris.

CONCLUSIONS

Isolation of stool-derived mucus is technically straightforward and can improve the performance of protein-based and/or nucleic acid-based approaches to CRC screening.

Brush cytology for the diagnosis of colorectal cancer

PURPOSE

The purpose of this study was to analyze the results of brush cytology for the diagnosis of colorectal cancer and compare them with the results of endoscopic biopsy and histologic evaluation of the resected specimen.

METHODS

Nine hundred eighteen patients who had brush cytology, endoscopic biopsy, and a definitive resection of a colorectal lesion between 1990 to 2006 were identified from our pathology database.

RESULTS

Cytology alone had a sensitivity of 88.2 percent, a specificity of 94.1 percent, a positive predictive value of 98.6 percent, and a negative predictive value of 61.9 percent for the diagnosis of colorectal cancer. Brush cytology always recognized malignant cells, with a positive predictive value of 100 percent. There was no significant difference between brush cytology and biopsy, which had a sensitivity of 86.9 percent, specificity of 98.1 percent, positive predictive value of 99.5 percent, and a negative predictive value of 60.3 percent. Combining the results of brush cytology and biopsy resulted in a statistically significant increase in sensitivity to 97.4 percent (P < 0.001), a significant increase in the negative predictive value to 88.4 percent (P < 0.001), and a significant reduction in the false-negative rate to 0.03 percent (P < 0.001) for the diagnosis of colorectal cancer.

CONCLUSIONS

Brush cytology is as accurate as endoscopic biopsy for the diagnosis of colorectal cancer, and combining these two diagnostic modalities resulted in a significant improvement in the definitive diagnosis of cancer, which might reduce the need for further biopsy.

Improved recovery of exfoliated colonocytes from feces using newly developed immunomagnetic beads

We demonstrated the feasibility of a new methodology for isolating colonocytes from feces. To reduce costs and improve the recovery rate of colonocytes from feces, we attempted to develop new immunomagnetic beads. Several sizes of magnetic beads were prepared and tagged with a monoclonal antibody against EpCAM. We made several new monoclonal antibodies against EpCAM, and each monoclonal antibody was tagged to the magnetic beads. In the simulation, the most efficient recovery of HT-29 cells was obtained using the smallest size of beads. Also, beads tagged with a monoclonal antibody with a higher affinity against EpCAM had a higher recovery rate. Similar results were obtained when the smallest size of beads with the highest-affinity monoclonal antibody was applied to clinical samples. The newly developed immunomagnetic beads may be useful for isolating colorectal cancer cells from feces, enabling the cytological or molecular biological diagnosis of CRC.

Detection of the DNA point mutation of colorectal cancer cells isolated from feces stored under different conditions

BACKGROUND

We reported on a novel diagnostic method for colorectal cancer (CRC) using a DNA-based analysis of isolated colonocytes from feces. The aim of the present study was to investigate with real-time PCR and direct sequencing analysis whether the cancer cells could be detected in feces stored under different conditions after evacuation.

METHODS

Feces were collected from patients with CRC. Feces were divided into 21 pieces and each piece was manipulated at time after arrival (zero time) and after storage of 24, 48 and 72 h at 4 or 37 degrees C. Colonocytes were isolated from each separate fecal sample, and DNA and RNA were extracted from the colonocytes. We investigated the relationship between storage conditions and content of extracted DNA or RNA with real-time PCR. We also clarified the gene alterations regarding APC and p53 genes under different storage conditions with direct sequence analysis.

RESULTS

Though the amount of genomic DNA and total RNA recovered from colonocytes isolated from each fecal piece decreased significantly at 37 degrees C at any storage time compared with 0 h, the gene alterations were detected independent of any storage conditions.

CONCLUSIONS

The colonocytes recovery rate from feces was unchanging for 3 days as long as the feces were kept at 4 degrees C. However, the identical point mutation to one obtained in cancer tissue was detected in the corresponding exfoliated colonocytes even after storage for 72 h at 37 degrees C, which suggests that exfoliated CRC cells maintain their configuration in feces at least 3 days after evacuation.

Detection of colorectal cancer cells from feces using quantitative real-time RT-PCR for colorectal cancer diagnosis

Early detection of colorectal cancer (CRC) is desired for reducing its mortality rate. Recently, the feasibility of a new method for isolating colonocytes from feces was demonstrated, followed by direct sequencing analysis for detecting colorectal cancer. In the present study, gene expression analysis was conducted using quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR). One hundred and sixty-six patients with CRC and 134 healthy volunteers were enrolled. Messenger RNA expressions of CEA, MMP7, MYBL2, PTGS2 and TP53 in the colonocytes isolated from feces were analyzed by quantitative real-time RT-PCR. Beta-2-microglobulin, used for internal control, could not be detected in approximately 25% each of the CRC patients (39/166) and healthy volunteers (33/134). CEA expression did not differ significantly between CRC patients and healthy volunteers (P = 0.21). MMP7, MYBL2, PTGS2 and TP53 gene expressions were significantly higher in CRC patients than in healthy volunteers (P < 0.001). The overall sensitivity and specificity using these gene expressions were 58.3% (74/127, 95% CI; 49.2-67.0) and 88.1% (89/101, 95% CI; 80.2-93.7), respectively. The sensitivity was dependent on the tumor location (P = 0.01) and tumor size (P = 0.02), but not the tumor depth (P = 0.06) or cancer stage (P = 0.37). Gene expression analysis of colonocytes isolated from feces may be a useful method for CRC screening, if the number of isolated colonocytes is sufficiently high for analysis by quantitative real-time PCR. Therefore, improvement of the colonocyte retrieval system from feces may be necessary for the technique to be developed for clinical use.

A novel magnetic bead-based assay with high sensitivity and selectivity for analysis of telomerase in exfoliated cells from patients with bladder and colon cancer

Telomerase activity is elevated in more than 85% of cancer cells and absent in most of the normal cells and thus represents a potential cancer biomarker. We report its measurement in colon and bladder cancer cells captured using antibody-coated magnetic beads. The cells are lysed and telomerase activity is detected using a biosensor assay that employs an oligonucleotide containing the telomerase recognition sequence also covalently coupled to magnetic beads. Telomerase activity is measured by the incorporation of multiple biotinylated nucleotides at the 3'-end of the oligonucleotide strands during elongation which are then reacted with streptavidin-conjugated horseradish peroxidase. A luminescent signal is generated when hydrogen peroxidase is added in the presence of luminol and a signal enhancer. LOD experiments confirm sensitivity down to ten cancer cell equivalents. The telomerase assay reliably identified patient samples considered by an independent pathological review to contain cancer cells. Samples from normal healthy volunteers were all telomerase negative. The assay, which is amenable to automation, demonstrated high sensitivity and specificity in a small clinical cohort, making it of potential benefit as a first line assay for detection and monitoring of colon and bladder cancer.

Probiotic bacteria change Escherichia coli-induced gene expression in cultured colonocytes: Implications in intestinal pathophysiology

AIM: To investigate the change in eukaryotic gene expression profile in Caco-2 cells after infection with strains of Escherichia coli and commensal probiotic bacteria.

METHODS: A 19200 gene/expressed sequence tag gene chip was used to examine expression of genes after infection of Caco-2 cells with strains of normal flora E. coli, Lactobacillus plantarum, and a combination of the two.

RESULTS: The cDNA microarray revealed up-regulation of 155 and down-regulation of 177 genes by E. coli. L. plantarum up-regulated 45 and down-regulated 36 genes. During mixed infection, 27 genes were up-regulated and 59 were down-regulated, with nullification of stimulatory/inhibitory effects on most of the genes. Expression of several new genes was noted in this group.

CONCLUSION: The commensal bacterial strains used in this study induced the expression of a large number of genes in colonocyte-like cultured cells and changed the expression of several genes involved in important cellular processes such as regulation of transcription, protein biosynthesis, metabolism, cell adhesion, ubiquitination, and apoptosis. Such changes induced by the presence of probiotic bacteria may shape the physiologic and pathologic responses they trigger in the host.

Cell exfoliation in the human colon: myth, reality and implications for colorectal cancer screening

Colonocyte exfoliation in the human colon constitutes a unique mechanism of cell population control that can undergo significant changes under different physiological and pathological conditions. Being closely related to the apoptosis and anoikis, cell exfoliation from colonic epithelium appears to be a relatively rare event in normal conditions, but its rate dramatically increases in neoplasia, when cell removal by apoptosis in situ does not function properly. Several studies show that significant numbers of exfoliated colonocytes are not lost in the faecal contents of the gut, but retained in the mucocellular layer overlying colonic mucosa. Recent observations allow hypothesizing that the mucocellular layer containing exfoliated colonocytes may gradually migrate distally, eventually leading to the accumulation of the cells exfoliated from malignant colorectal tumours on the surface of the rectal mucosa. Implications of exfoliated colonocyte analysis to colorectal cancer screening and early diagnosis are discussed.

Molecular biomarkers for cancer detection in blood and bodily fluids

Cancer is a major and increasing public health problem worldwide. Traditionally, the diagnosis and staging of cancer, as well as the evaluation of response to therapy have been primarily based on morphology, with relatively few cancer biomarkers currently in use. Conventional biomarker studies have been focused on single genes or discrete pathways, but this approach has had limited success because of the complex and heterogeneous nature of many cancers. The completion of the human genome project and the development of new technologies have greatly facilitated the identification of biomarkers for assessment of cancer risk, early detection of primary cancers, monitoring cancer treatment, and detection of recurrence. This article reviews the various approaches used for development of such markers and describes markers of potential clinical interest in major types of cancer. Finally, we discuss the reasons why so few cancer biomarkers are currently available for clinical use.