Fecal protein markers of colorectal cancer

To identify fecal proteins that might prove useful in the early detection of colorectal cancer, we used sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and protein immunoblotting to compare the fecal protein patterns of stool supernatants from 10 patients with colorectal cancer with those of 12 controls. SDS-PAGE followed by Coomassie blue staining revealed two heavily stained bands in the majority of cancer stools that were not present in control stools. These bands proved to be human hemoglobin and human albumin by protein immunoblotting. No other consistent differences between the cancer and control stools were observed on the stained gels. The stool supernatants were probed for several other blood proteins by protein immunoblotting. Carbonic anhydrases I and II were more abundant in the cancer stools; alpha 1-antitrypsin appeared equally in cancer and control stools. Further work is needed to determine whether measurement of fecal carbonic anhydrase can be useful for early detection of colorectal cancer.