Immunodiscrimination of colorectal neoplasia using MUC1 antibodies: discrepant findings in tissue versus stool

The immune interactions of gut glycans and microbiota in health and disease

The human digestive system harbors a vast diversity of commensal bacteria and maintains a symbiotic relationship with them. However, imbalances in the gut microbiota accompany various diseases, such as inflammatory bowel diseases (IBDs) and colorectal cancers (CRCs), which significantly impact the well-being of populations globally. Glycosylation of the mucus layer is a crucial factor that plays a critical role in maintaining the homeostatic environment in the gut. This review delves into how the gut microbiota, immune cells, and gut mucus layer work together to establish a balanced gut environment. Specifically, the role of glycosylation in regulating immune cell responses and mucus metabolism in this process is examined.

The Mucin Family of Proteins: Candidates as Potential Biomarkers for Colon Cancer

Mucins (MUC1-MUC24) are a family of glycoproteins involved in cell signaling and barrier protection. They have been implicated in the progression of numerous malignancies including gastric, pancreatic, ovarian, breast, and lung cancer. Mucins have also been extensively studied with respect to colorectal cancer. They have been found to have diverse expression profiles amongst the normal colon, benign hyperplastic polyps, pre-malignant polyps, and colon cancers. Those expressed in the normal colon include MUC2, MUC3, MUC4, MUC11, MUC12, MUC13, MUC15 (at low levels), and MUC21. Whereas MUC5, MUC6, MUC16, and MUC20 are absent from the normal colon and are expressed in colorectal cancers. MUC1, MUC2, MUC4, MUC5AC, and MUC6 are currently the most widely covered in the literature regarding their role in the progression from normal colonic tissue to cancer.

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

GRAPHICAL ABSTRACT

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.

Molecular detection of colorectal neoplasia

A variety of noninvasive molecular approaches to colorectal cancer screening are emerging with potential to improve screening effectiveness and user-friendliness. These approaches are based on the sensitive assay of molecular markers in stool, blood, and urine samples. New methods, especially next generation stool-based tests, have been shown to detect both colorectal cancers and precancerous lesions with high accuracy. Validation of these technologies in average-risk populations are needed to establish their role for general colorectal cancer screening. This review addresses the biological rationale, technical advances, recent clinical performance data, and remaining issues with molecular screening for colorectal cancer.

Humoral immune response to abnormal MUC1 in subjects with colorectal adenoma and cancer

Colorectal cancer (CRC) expresses a hypoglycosylated (abnormal) form of MUC1 different than MUC1 expressed in normal colon, which elicits antibodies in patients with CRC. This form of MUC1 is expressed in other abnormal but non-malignant lesions in the colon, such as adenomatous polyps, precursors to CRC. Estimates of the prevalence of anti-MUC1 antibodies in subjects with these lesions are lacking. We evaluated IgM and IgG anti-MUC1 antibodies in 148 subjects with non-advanced adenomas (NAA), advanced adenomas (AA), colorectal cancer, hyperplastic polyps (HPP), and normal controls. We hypothesized that the prevalence of anti-MUC1 antibodies would increase along the adenoma-carcinoma sequence as more dysplastic tissues express more abnormal MUC1. Anti-MUC1 IgM was found in 5/47 (10.6%) of normals, 5/45 (11.1%) of NAA, 7/47 (14.9%) of AA, and 4/20 (20.0%) of CRC (p=0.70). The prevalence of anti-MUC1 IgG was 8/47 (17.0%) of normals, 14/45 (31.1%) of NAA, 14/47 (29.8%) of AA, and 6/20 (30.0%) of CRC (p=0.36). We found no significant differences in the prevalence of anti-MUC1 antibodies between subjects along the adenoma-carcinoma sequence. However, in an exploratory analysis, the median normalized anti-MUC1 IgG OD level of the combined abnormal groups (NAA, AA, CRC) was significantly higher than the normals (0.045 OD vs. 0.030 OD; p=0.017). Our data support further studies into the potential role of anti-MUC1 immunity in preventing progression of premalignant colon lesions to colon cancer.

Detection of colorectal disease by stool defensin assay: an exploratory study

BACKGROUND & AIMS

Alpha-defensins 1-3 (human neutrophil peptides [HNP]1-3), reported to be elevated in tumor tissue and serum of patients with colorectal cancer (CRC), have not been studied in stool. We evaluated the neoplasm specificity of HPN1-3 and their discriminant value as stool markers for CRC.

METHODS

Protein and mRNA expression of HPN1-3 were assayed in CRC cell lines, microdissected CRC and normal epithelium, and white blood cells. HNP1-3 proteins in stools were quantified in blinded fashion from 30 normal subjects, 20 patients with CRC, 10 with a large colorectal adenoma, 10 with upper gastrointestinal cancer, and 10 with IBD. Stool lactoferrin was also quantified.

RESULTS

HPN1-3 proteins were not detected in CRC cell lines but were high (>4000 ng/mL) in white blood cells. mRNA levels of HPN1-3 were comparably low in CRC cell lines, microdissected CRC, and normal colon epithelium, but they were >1000-fold and >30,000-fold higher in white blood cells and neutrophils, respectively. Mean stool HPN1-3 levels were 17 ng/mL with normals, 125 ng/mL with CRC, 62 ng/mL with adenoma, 63 ng/mL with upper gastrointestinal cancer, and 231 ng/mL with IBD (P < .01 for each patient group vs normals). HPN1-3 levels in IBD were higher than in CRC (P = .04). At 90% specificity, sensitivity of stool defensins was 35% for CRC, 40% for adenoma, 40% for upper gastrointestinal cancers, and 80% for IBD. Stool defensins and lactoferrin levels correlated (R2 = 0.70, P < .001).

CONCLUSIONS

Alpha-defensins 1-3 levels are nonspecifically elevated in stools from patients with colorectal neoplasia and likely originate from white blood cells. Alpha-defensins 1-3 in stool might serve as markers of inflammatory bowel conditions.

Stool screening for colorectal cancer: molecular approaches

Assay of molecular markers in stool represents a promising noninvasive approach to screen colorectal cancer. Given that neoplasms exfoliate abundantly into the lumen and that DNA recovered from stool can be assayed with sensitive techniques, there is a strong biologic rationale to pursue this emerging technology. A challenge with DNA-based testing relates to the selection of markers. Because of the molecular heterogeneity of cancer, no single marker has yielded perfect sensitivity. Several combinations of markers in early stool assays have produced high detection rates of both colorectal cancer and advanced adenomas in selected patient groups, but observations from large representative populations are lacking at present. Potential expanded applications of stool DNA testing include detection of supracolonic aerodigestive cancers and of dysplasia in inflammatory bowel disease. Further marker discovery and technologic refinements should translate into improved test performance and fuel a continued evolution with this screening approach.

Identification of colon cancer patients by molecular diagnosis

The important causal role of DNA alterations in cancer development implies that tumor specific DNA mutations might serve as ideal parameters in cancer diagnosis. In particular the detection of mutations in fecal DNA might complement the current methods for the early diagnosis of colorectal tumors. Over the last 10 years many studies have proven the usefulness and the feasibility of the fecal DNA analysis in the diagnosis of colon tumors. Technical difficulties have circumvented the clinical application and the broad screening by molecular diagnosis. Recent methodological proceedings together with the promising outcomes of first multi-target studies have put a diagnostic stool-based DNA test for colorectal tumors within close reach.

Mucins in gastrointestinal cancers

The mucin family has been under study by molecular biologists, biochemists, pathologists and immunologists interested in cancer because of the role these molecules can play in the diagnosis and treatment of cancer. Immense knowledge has been accumulated, but the high speed of progress in the laboratory has not been matched by the progress towards applying this knowledge in the clinic. For example, specific knowledge of cancer-associated changes in the expression and glycosylation of various mucins, which can aid in the diagnosis as well as prognosis of GI cancers, has not yet led to the use of a panel of anti-mucin antibodies as a standard diagnostic tool. Similarly, many more opportunities exist for using mucin-based therapies than are currently being considered in the clinic. This chapter aimed to highlight some of these opportunities and to interest clinician scientists in exploring them in the near future.