Fecal alpha 1-antitrypsin detection of colorectal neoplasia. An evaluation using HemoQuant

Murine fecal proteomics: a model system for the detection of potential biomarkers for colorectal cancer

Tumor related products shed into the feces offer a potential source of biomarkers for the detection of colorectal cancer (CRC). Using SDS-PAGE followed by nanoflow reversed-phased LC-MS/MS to analyse fecal samples from Apc(Min/+) mice (that develop spontaneous multiple intestinal neoplasia with age) we have identified 336 proteins (115 proteins of murine origin, 201 from fecal bacteria, 18 associated with food intake and 2 of apparent parasitic origin). 75% of the murine proteins identified in this study are predicted to be extracellular or associated with the cell plasma membrane. Of these proteins, a number of the murine homologues of colorectal cancer associated proteins (CCAP) such as hemoglobin, haptoglobin, hemopexin, alpha-2-macroglobulin and cadherin-17 have been identified, demonstrating the potential of fecal proteomics for detecting potential biomarkers and paving the way for subsequent MS/MS based biomarker studies on similar human samples.

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.

Molecular stool screening for colorectal cancer

BACKGROUND

Mass screening for colorectal cancer reduces mortality and, with recent advances in molecular genetics, molecular stool-based tests have produced promising results. This article reviews this innovation and discusses its clinical significance.

METHODS

Medline searches were used to identify recent key articles relating to stool-based testing. Further articles were obtained by manual scanning of the reference lists of identified papers.

RESULTS

Current screening methods are based on endoscopic, radiological and stool-based testing. Recent recognition of the adenoma-carcinoma sequence and pathophysiological studies of colonic epithelium have enabled tumour markers to be used in the screening setting. Non-invasive molecular stool testing has now been shown to have a high sensitivity and specificity.

CONCLUSION

Recent studies on molecular stool-based testing have shown higher sensitivity and specificity than earlier studies, but larger clinical trials are required. Laboratory methods are still undergoing research, with the aim of improving sensitivity to allow large-scale testing.

Prospective evaluation of fecal calprotectin as a screening biomarker for colorectal neoplasia

OBJECTIVES

Stool testing is a well established method of screening for colorectal neoplasia. Emerging data suggest that novel biomarkers may offer performance advantages over fecal occult blood. In this large, prospective study, we assessed fecal calprotectin (a leukocyte-derived protein) as a screening biomarker for colorectal neoplasia. Fecal calprotectin was directly compared to fecal hemoglobin (Hb) and colonoscopy as the existing criterion standards for stool screening and structural evaluation, respectively.

METHODS

Subjects included colonoscopy patients with a personal history of colorectal neoplasia, family history of colorectal cancer, or iron deficiency anemia. Stool specimens were collected before purgation, processed appropriately, and quantitatively analyzed for calprotectin (Nycomed Pharma, Oslo, Norway) and for Hb (Mayo Medical Laboratories, Rochester, MN) by masked technicians. Colonoscopies were performed by experienced endoscopists without prior knowledge of the fecal assay results.

RESULTS

Among 412 subjects, 97 (24%) subjects had one or more colorectal neoplasms (including three with adenocarcinomas). Fecal calprotectin levels did not differ significantly between subjects with versus subjects without colorectal neoplasms (p = 0.33). Neither tumor number (p = 0.85) nor tumor size (p = 0.86) significantly influenced the observed fecal calprotectin concentrations. Estimates of the sensitivity, specificity, and positive and negative predictive values of fecal calprotectin for any colorectal neoplasms were 37%, 63%, 23%, and 76%, respectively. Comparable performance estimates for fecal Hb were 3%, 97%, 27%, and 77%, respectively.

CONCLUSIONS

In this cohort of colonoscopy patients at above average risk, fecal calprotectin was a poor screening biomarker for colorectal neoplasia. Further investigation of tumor-derived, rather than blood-based, biomarkers may be a more rewarding approach to stool screening for colorectal neoplasia.

Two cases of severe iron-deficiency anaemia due to inflammatory bowel disease in the dog

Two dogs were referred for investigation of lethargy and anaemia. Preliminary examinations by the referring veterinary surgeons had revealed severe anaemia, which was poorly regenerative. In one case, the anaemia was microcytic and, in the other, it was hypochromic. These findings were suggestive of chronic blood loss anaemia. Neither dog had external signs of gastrointestinal disease, although one had vomited on a single occasion during the two weeks preceding referral. Although both dogs were producing grossly normal faeces, further investigations detected faecal occult blood. Multiple full thickness gastrointestinal biopsies were taken at laparotomy. These showed segmental eosinophilic enteritis of the duodenum and proximal jejunum in one case, and marked chronic lymphocytic gastritis in the other. Both cases illustrate the fact that severe systemic disease can result from gastrointestinal pathology in the absence of clinical signs of gastrointestinal disease.