Noninvasive colorectal cancer screening

Abnormal mucin with the STn epitope is produced by colorectal cancer cells and is immunologically distinguishable from normal colonic mucin. Herein we describe a technique of detecting abnormal mucin in fecal samples as a method of screening for colorectal neoplasia. Soluble glycoproteins from fecal samples of patients with symptoms of bowel disease and asymptomatic volunteer subjects were isolated by centrifugation and ethanol precipitation. The protein content of the soluble fraction was normalized and tested by immunoassay (slot dot). Anti-COTA monoclonal antibody SP-21, which reacts with STn epitope, was applied in the reaction, and the optical density of each slot dot was determined by imaging densitometer. Quantitative values of samples were determined from the standard curve obtained with highly purified COTA. COTA values >15 g/ml were considered positive for neoplasia. Results indicated that 5/6 colon cancers, 6/22 adenomas, 1/8 colitis cases, and 2/58 normal patients were positive in the test. The pilot study revealed that COTA assay is sensitive and more specific than Hemoccult screening for colorectal neoplasia.