Release of decay-accelerating factor into stools of patients with colorectal cancer by means of cleavage at the site of glycosylphosphatidylinositol anchor.

The expression of decay-accelerating factor (DAF), a cell-membrane-complement regulator, is enhanced in colorectal cancer, and DAF is detected in the stools of patients with colorectal cancer. In this study, to elucidate mechanisms whereby DAF is released into the colonic lumen, we analyzed and compared the properties of DAF in stools and colorectal-cancer tissues. Stool specimens taken before surgery and tissue samples from surgically resected colorectal cancers were obtained from 21 patients.

Improvements in the measurement of stool decay-accelerating factor in the detection of colorectal cancer.

We have previously developed an enzyme-linked immunosorbent assay (ELISA) to measure stool decay-accelerating factor (DAF) and found that stool DAF concentrations were significantly elevated in patients with colorectal cancer, suggesting that the measurement of stool DAF may be valuable for the detection of colorectal cancer. In order to refine the assay for the measurement of stool DAF, we investigated 1) effects of centrifugation of stool samples, 2) effects of detergents, and 3) adequate combination of various anti-DAF monoclonal antibodies for the ELISA system using only monoclonal antibodies. We found that high-speed centrifugation could be omitted and that only the removal of large undigested food residues by centrifugation of short duration in a low-speed benchtop microcentrifuge sufficed to adequately prepare the stool samples.