A test for detection of colorectal cancer

Rectal mucosal quantitative galactose oxidase-Schiff reaction as an early detection biomarker for colorectal cancer: comparison to fecal occult stool blood test

The galactose oxidase-Schiff (GOS) reaction detects D-galactose-β-[1,3]-N-acetyl-D-galactosamine. This is a T-antigen expressed in mucus from malignant cells and colonic mucosa adjacent to cancer but not in normal mucosa. Previous studies using a qualitative GOS assay proved to be of limited value for the detection of colorectal neoplasia. We used a newly developed quantitative GOS assay to determine its potential as an early detection biomarker for colorectal cancer. We completed a multi-center, prospective, cross-sectional cohort validation study consisting of 70 normal controls, 23 high-risk normal patients (polyp history or family history of colorectal cancer (CRC) with currently normal colonoscopy), 137 patients with adenomatous polyps, and 69 with colorectal cancers. Prior to colonoscopy, two samples of stool were collected via a rectal exam: one for FOBT, and one for GOS. The area under the ROC curve (AUC) for detecting colonic adenomas and cancer for normal colons, computed with logistic regression was 0.69 for GOS, 0.62 for FOBT, and 0.73 for GOS combined with FOBT. Adding GOS to FOBT did not significantly change the ROC of FOBT alone. GOS does not appear to be a suitable marker of colorectal neoplasia.

Comparison of a peanut agglutinin test and an immunochemical faecal occult blood test in detecting colorectal neoplasia in symptomatic patients

BACKGROUND

Currently available methods for detection of early-stage colorectal cancer are reliant on faecal occult blood (FOB) tests. Bleeding, however, is not specific for colorectal neoplasia. Enzymatically detected or peanut agglutinin (PNA)-detectable galactose-beta1-3-N-acetyl-galactosamine residues found in rectal mucus have been used to detect colorectal cancer.

METHODS

The sensitivity and specificity of the PNA rectal mucus test were compared with those of an immunological test for faecal occult blood (Hemolex) in 199 symptomatic patients referred for colorectal investigations. All patients also underwent a colonoscopy. SDS-PAGE and PNA-overlay were used to characterize PNA-binding proteins in normal and malignant colorectal tissue.

RESULTS

The PNA test had a similar sensitivity to that of Hemolex for colorectal carcinoma (83% vs. 72%), adenomas (55% vs. 50%), inflammatory bowel disease (52% vs. 48%) and hyperplastic polyps (48% vs. 25%). The sensitivity of the PNA test and Hemolex for colorectal neoplasia was 69% vs. 59% and specificity 68% vs. 86% (p=0.002). SDS-PAGE and PNA-overlay showed some commonly expressed PNA-binding proteins in both normal mucosa and colorectal cancer and a higher and even selective expression of 160 kD PNA-binding protein in colorectal cancer.

CONCLUSIONS

A single PNA test in its present form is as sensitive an indicator of colorectal neoplasia as Hemolex completed over three days, but lacks specificity. The 160 kD cancer-associated antigen we have identified is under further characterization for development of a more specific PNA test.

Oral Contrast Adherence to Polyps on CT Colonography

Although oral contrast agents are known to improve the accuracy of CT colonography (CTC) by tagging fluid and stool, it is not well recognized that oral contrast also adheres to the surface of polyps. The authors' objective was to quantitate the frequency of contrast adhering to polyps. Three hundred thirty-eight optical colonoscopy-proven polyps were identified on CTC of all of the 216 patients with polyps in a larger cohort of screening patients. CT scans of polyps were analyzed for adherent contrast (ie, a thin coat/adherent drops) in at least one view (prone/supine). Forty-six percent of the 312 polyps not touching a contrast pool had adherent contrast. Polyps with villous histology were significantly more likely to have adherent contrast (77% [20/26] vs. 43% [124/286], P<0.001). Oral contrast agents often tag polyp surfaces in a pattern that is distinct from internal tagging of adherent stool, which must be recognized during CTC interpretation. Polyps with villous histology show a higher rate of contrast adherence than nonvillous polyps.

Coprocytobiology: on the nature of cellular elements from stools in the pathophysiology of colonic disease

The gastrointestinal epithelium is known to undergo constant and rapid renewal resulting in millions of cells being shed into the fecal stream every day. The conventional wisdom was that these cells disintegrate upon exfoliation and will not survive the transit through the intestinal tract. In 1990, we (P.N.) made the discovery that a significant number of these cells remain intact and viable and that they can be isolated. The implications of this important discovery became apparent when we demonstrated that these cells are exclusively of colonic origin, are anatomically representative of the entire colon, and can be used for clinical investigations of disease processes. The term coprocytobiology (CCB) was coined to encompass the broad range of applications of this new technology. The somatic cell sampling and recovery (SCSR) process involves the isolation of exfoliated colonocytes from a small sample of stool ( approximately 1 g) collected and transported in a unique medium at ambient temperature, providing cells for the detection of a number of biomarkers of disease propensity. These exfoliated colonocytes express cytokeratins indicating epithelial lineage as well as colon-specific antigen. Over the years, the study of exfoliated colonocytes has provided striking new insights into the biology of colon cancer and inflammatory bowel disease, including detection of p53 gene mutations, reverse transcriptase polymerase chain reaction amplification, and identification of CD44 splice variants, neoplasia-associated specific binding of plant lectins, and expression of COX-2, the inducible form of cyclooxygenase. The functional diversity of cells isolated by SCSR is revealed by the demonstration of cell surface markers such as secretory component, IgA, and IgG on the one hand and the amplification and cloning of the human insulin receptor and the expression of the multidrug resistance gene mdr-1 on the other hand. This review portrays the immense potential of CCB as a powerful tool for investigating the pathophysiology of disease, identifying genetic variants in pharmacogenetics, assessment of mucosal immunity, and several other applications that use somatic cells.

Early detection for colorectal cancer: new aspects in fecal occult blood screening

The authors report on promising diagnostic methods of occult intestinal bleeding and discusses the potential new strategy of early detection of colorectal carcinomas in respect to old and new diagnostic measures available. Because of the limited sensitivity and specificity of classical methods used for the demonstration of occult fecal blood, the authors recommend the introduction of new techniques and markers in screening practice. It is presumed that new discoveries in molecular biology will improve the accuracy of early colorectal cancer prevention. Their implementation into routine screening, however, will not take place in the near future. Until their realization, improved screening efficacy is expected from the use of more specific and sensitive blood tests.

Detection of colorectal neoplasia with peanut-agglutinin (PNA)-reactive carbohydrate structures in rectal mucus

In contrast to normal colorectal mucosa, peanut-agglutinin-(PNA)-reactive glycoconjugates are commonly expressed in most colorectal carcinomas and in some pre-malignant conditions such as adenomas and ulcerative colitis. Since enzymatically detectable galactose-beta1-3-N-acetyl-galactosamine residues are found in rectal mucus obtained from patients with carcinoma of the large bowel, it was investigated here whether PNA-reactive carbohydrate structures in rectal mucus can be exploited in the detection of colorectal neoplasia. Samples of rectal mucus obtained from 261 randomly selected patients with colorectal symptoms were applied on nitrocellulose filters. The presence of PNA-reactive glycoconjugates in mucus samples was determined by a peroxidase-conjugated PNA-overlay procedure. The results were correlated to findings from total colonoscopy/surgery and histopathology. PNA-reactive carbohydrate structures were detected in 76% of patients with carcinoma (p < 0.005), in 62% of patients with adenoma (p < 0.005), in 69% of patients with inflammatory bowel disease (p < 0.005), and in 38% of patients with hyperplastic polyps (NS), in contrast to 21% of the control subjects with macroscopically normal colorectal mucosa. These results show that PNA-reactive carbohydrate alterations in rectal mucus correlates with neoplastic and hyperproliferative conditions of the colorectal mucosa. The specificity of the PNA test for colorectal neoplasia was 76%. Therefore the use of more discriminate carbohydrate probes are needed for the pre-symptomatic detection of colorectal neoplasia.

Mucosal origin and shedding of an early colonic tumor marker defined by Adnab-9 monoclonal antibody

Recent attention has been drawn to the diagnostic potential of tests based on shed colonic tumor markers. Adnab-9 monoclonal antibody raised against neoplastic, potentially premalignant colonic adenomas recognizes a marker in colonic effluent or tissue which correlates with the presence of tumors or risk of colorectal cancer. The origin of this antigen and optimal collection of colonic effluent were investigated by enzyme-linked immunosorbent assay and Western blotting. Mean Adnab-9 binding in effluent samples from colorectal cancer patients even after resection is high as compared with that in normal subjects (P < 0.05). Effluent samples are best collected in the morning hours. Antigen proteolysis may be significant depending on the site and timing of effluent collection, but breakdown products are reactive. Tissue and effluent Adnab-9 binding at any one anatomic site of collection appear to correlate (r = 0.88, P = 0.01). The Adnab-9 antigen is constitutively expressed at low levels throughout the distal bowel and localized to the deepest regions of the mucosal crypts. Other than meconium, no significant levels of binding are found in other body fluids. This antigen is specific for the gastrointestinal tract, its binding in conveniently collected effluent samples correlates with tissue content, and the antigen is constitutively expressed in the crypts of the distal small bowel and colonic mucosa.

Evaluation of a new test for colorectal neoplasms: a prospective study of asymptomatic population

In a recent pilot study, we have suggested of potential usefulness of a new test (Shams' test) for screening colorectal (CR) cancer in Japan. Although the sensitivity of this test was remarkably high, its accurate specificity was unclear. The purpose of our present study is to evaluate the incidence of non-specific reaction of Shams' test in the normal Japanese populations. We analyzed 330 asymptomatic individuals, who were seen for annual health checkup, for the presence of the tumor marker D-Gal-B (1- > 3)-D-GalNAc in their rectal mucin. The rectal mucin was smeared on nitrocellulose membrane filter and developed by a sequential reaction of B-D-galactose oxidase and Schiff's reagent. Immunological fecal occult blood test (FOBT) was done in parallel. Extensive study by barium enema/total colonoscopy was indicated only for those who showed positive results with Shams' test or FOBT. A total of 271 individuals were negative, while 50 and 9 had positive and equivocal (+/-) results, respectively. Subsequent barium enema and fiberoptic proctocolonoscopic examinations, which were available on 32 of 59 cases, revealed 6 adenomatous polyps, one villous adenoma with focal severe atypia, and 4 cases of diverticular disease. Except for one patient with polyp, 6 other patients harboring polyps were negative with immunological FOBT. The overall specificity of Shams' test was 92.2% (271/294). Based on these results and preceding reports, we concluded that Shams' test could be a useful tool in our strategy for early detection of CR neoplasms and precancerous lesions.

A pilot study on the usefulness of a new test for mass screening of colorectal cancer in Japan

A new screening test (Shamsuddin and Elsayed, 1988) based on the enzymatic detection of the disaccharide beta-D-Gal(1----3)-D-GalNAc in the rectal mucus of patients with colorectal (CR) cancer and precancerous conditions such as inflammatory bowel disease (IBD) and polyp (precancerous lesions) was evaluated in 85 Japanese patients. Following a 15-minute reaction, a sensitivity of 80.0% (8/10) for CR cancer and 72.2% (8/11) for precancerous lesions was obtained. The overall specificity for combined CR cancers and precancerous lesions was 62.2% (28/45). Correlation with abnormal mucin production in the tissues of CR cancer and precancerous lesions was studied by high-iron diamine-Alcian blue and/or periodic acid-Schiff-Alcian blue (pH = 1.0). The agreement of the results with this test was 77.8% (7/9) for CR cancers and 75.0% (6/8) for precancerous conditions. Because of the simplicity of this test, low cost, stability of the sample and reagents and accuracy for CR cancer and precancerous lesions, the test may have potential use for mass screening of cancer and high risk individuals, particularly CR cancer in Japan.