Oral colon lavage solutions containing polyethylene glycol may interfere with ELISA detection of tumor-associated antigens in colonic effluent

Rectal effluent as a research tool

Studies of localized secretions are generally superior to those of blood because they contain higher concentrations of molecules specific to the organ of interest. A common method used to analyze localized secretions is lavage. The flow of fluid over the lining of a cavity picks up both cells and soluble factors, and the effluent can be collected for study. Gastrointestinal (GI) lavage is easily and noninvasively performed by the administration of gut lavage solutions such as those routinely given to patients prior to colonoscopy, with GI lavage fluid being the copious, watery rectal effluent subsequently induced. Residual effluent is currently suctioned from the colon and discarded during colonoscopy. With millions of routine colonoscopies performed per year, GI lavage fluid is a rich and largely untapped resource for basic and clinical research. Rectal effluent can also be easily collected in a toilet receptacle without need for a colonoscopy. Rectal effluent generated in this manner has been used to study diarrheal disease, mucosal immunology, inflammatory bowel disease, celiac disease, and cancer. It is often referred to as gut lavage, colon lavage, GI lavage, or whole gut lavage fluid, which makes it challenging to locate previous studies in the literature and there are currently no comprehensive reviews of its use as a research tool. This review attempts to fill this void by discussing previous applications of rectal effluent in research and the methods that have been developed for its collection, stabilization, and analysis.

The use of early and midpoint adenoma-carcinoma sequence biomarkers in prediction of neoplastic progression in patients with a history of colorectal neoplasia

Since significant neoplasia after initial colonoscopy is low, we conducted this pilot study to compare the predictive role for colorectal neoplasia recurrence of anti-DCC with that of Adnab-9 binding to colonic effluent of high-risk patients. DCC and Adnab-9 effluent ELISA were performed at baseline colonoscopies. The results of follow-up colonoscopies were reviewed. To ensure specificity, immunohistochemistry and Western blot was performed with anti-DCC and for Adnab-9 where optimal fixation times were also evaluated. Mean follow-up was 2.6 years. Of 21 patients, 6 of 10 who progressed to CRN and 2 of 11 who did not had a positive Adnab-9 ELISA result (P=0.08). Despite an initial good correlation with Adnab-9 ELISA results in a smaller dataset, we were unable to obtain consistent subsequent DCC immunohistochemistry or Western blot data using antibody from two different sources. However, the original dataset of Adnab-9 results was reproducible on repetition of the ELISA with a larger set of samples that included this initial dataset and optimal fixation time was 20 min. We conclude that Adnab-9 appears to be a promising prognostic marker for neoplasia in the high-risk population. Industry standards need to be developed for DCC monoclonal antibodies that may have similar utility.

Colorectal cancer risk: the impact of evidence of a field effect of carcinogenesis on blinded diagnosis using an anti-adenoma antibody test performed on colonoscopic effluent

To better define high-risk populations for colorectal cancer screening, we used anti-adenoma antibody Adnab-9, comparing colonic effluent and tissue field effects from 45 high-risk and 11 control patients. We included Adnab-9 binding at the tissue level to elucidate the impact of a field effect of carcinogenesis contributing to the outcome of the effluent binding test. In high-risk patients, 64% of the left-sided effluent samples were positive (P < 0.002); 67% showed a field effect (P < 0.006); 82% of combined tests were positive (P < 0.001), as compared to 9%, 18%, and 27% respectively, of controls. Adnab-9 binding correlates with increased colorectal cancer risk associated with a field effect of carcinogenesis.

Carcinoembryonic antigen family of adhesion molecules in the cotton top tamarin (Saguinus oedipus)

Humans and the cotton top tamarin, a model for colitis and colorectal cancer, share carcinoembryonic antigen (CEA) moieties. We quantified CEA in colonic washings and extracts in both, and CEA bands were confirmed by Western blot. We compared CEA-family expression in tissues and serum in the tamarin with that of the common marmoset, which develops colitis but not cancer. CEA levels are higher in tamarin washings compared with humans, and higher than in marmosets extracts (P<0.005). CEA molecular species appear to be specific, and human CEA-family member epitopes are also found in these primates. The higher CEA levels in the tamarin may reflect the overall higher cancer prevalence.

Urinary organ specific neoantigen. A potentially diagnostic test for colorectal cancer

Urinary organ-specific neoantigen from colorectal cancer patients has been used to make a monoclonal antibody, BAC 18.1. In this study we assessed the potential of this antibody for the diagnosis of colorectal cancer. We evaluated binding in both urine and effluent samples and compared it with effluent carcinoembryonic antigen standardized for both volume (nanograms per milliliter) and protein. Urinary organ-specific antigen as detected by BAC 18.1 was significantly greater in 29 cancer patients (A405: 0.717 +/- 0.500) vs 27 controls [0.121 +/- 0.273 (P < 0.05)]. Considerable overlap of binding of BAC 18.1 was observed in the colonic effluent of patients with CRC (N = 13), adenomas (N = 26), inflammatory bowel disease (N = 8), or having a normal colonoscopic examination (N = 24). CEA levels (nanograms per milliliter) were significantly elevated in the effluent samples of patients with a past history of colorectal cancer, as compared to that of normal individuals (P < 0.05). The presence of the M(r) 30,000 organ-specific neoantigen in colonic effluent was also demonstrated by western blot. Organ-specific neoantigen originates in the colon and is excreted into the urine, so the BAC 18.1 binding levels in the urine may be a diagnostic aid for CRC.

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.

Adenoma-derived antibody, Adnab-9 recognizes a membrane-bound glycoprotein in colonic tissue and effluent material from patients with colorectal neoplasia

The binding in pre-colonoscopic effluent of Adnab-9, a monoclonal antibody raised against colonic adenomas, was evaluated for specificity in the diagnosis of colorectal cancer. A heterogeneous group of 58 patients was evaluated by ELISA. Effluent samples and tissue extracts were subjected to Western blotting or ELISA to confirm specificity. Immunohistochemistry was performed on the cancer tissue sections. The proportion of positive effluent binding was higher in the cancer when compared to the normal group (P = 0.036). A dominant 87 M(r) band was found in adenoma extracts and some effluent samples. Adnab-9 binding in effluent samples predominated in membrane-bound fractions. Immunohistochemistry showed no specific staining in the cancer cells. The antigen recognised is a glycoprotein shown by effects of N-glycanase digestion and not cross-reactive with carcinoembryonic antigen. Non-gastro-intestinal tissue extracts did not bind Adnab-9. The major 87 M(r) adenoma-derived antigen may be found in effluent material, particularly in the membrane-bound fraction.

Detection of carcinoembryonic antigen in colonic effluent by specific anti-CEA monoclonal antibodies

To characterize the CEA in colonic effluent, anti-CEA monoclonal antibody COL-4 was used in a qualitative radioimmunoassay in both fractionated and unfractionated colonic effluent. Both effluent samples and tissue extracts, were subjected to Western blotting and tissue sections to immunohistochemistry. Quantitative levels of colonic effluent CEA were determined by a kit (Abbott-EIA). Higher mean values of COL-4 binding activity were seen only in patients with a past history of polyps (P < 0.01). Quantitated CEA correlated with the presence of colorectal cancer (CRC) as compared to normal subjects, (1133 +/- 875 vs. 459 ng/ml +/- 602, P < 0.05) but not when standardized for protein content. COL-4 reacted with an 180,000 M(r) CEA in the effluent and activity was associated with membrane fraction of the effluent, but bore no relation to the immunohistological staining. We conclude that CEA is detectable in colonic effluent and is membrane associated, but the overlapping values in effluent samples do not make this a useful test in the diagnosis of CRC.