Analysis of tumor-associated antigen in feces from patients with colorectal cancer by immunoblotting

The tumor-associated antigen (TAA) in feces from patients with colorectal cancer (39 cases), colorectitis (9 cases), enteric polyps (12 cases), and normal controls (36 cases) were assayed by SDS-PAGE and immunoblotting with five monoclonal antibodies (McAbs) (CL-3, CL-4, CS-1, GS-2, and PS-10). The results showed that the number of protein bands in feces from patients with colorectal cancer was significantly higher than that in normal controls. The average number of TAA bands reacted with five McAbs in feces from patients with colorectal cancer was higher than that in enteritis and colorectal polyps. High molecular weight TAA fragments (>80 kD) were usually expressed in cancer, but none or few were found in normal controls, hyperplastic polyps, and enteritis. The positive rates of TAA in feces detected by CL-3, CL-4, CS-1, GS-2, and PS-10 were: colorectal cancer-73%, 70%, 41%, 63%, and 52%; normal controls-4%, 10.5%, 0%, 0%, and 10.5%; polyps-17%, 8%, 8%, 33%, and 8%; enteritis-22%, 22%, 33%, 44%, and 11%, respectively. Therefore, CL-3 and CL-4 McAbs may be useful for the diagnosis of colorectal cancer.