Sucrase-isomaltase: a marker associated with the progression of adenomatous polyps to adenocarcinomas.

Adenocarcinomas of the colon arise from adenomatous polyps. We hypothesized that sucrase-isomaltase (SI), a glycoprotein hydrolase, found in normal small intestine, fetal colon, and colon carcinomas is a marker associated with progression of adenomatous polyps with dysplasia to adenocarcinomas. To examine this hypothesis, we performed immunostaining using a polyclonal antihuman SI antibody in 32 adenomatous polyps with varying degrees of dysplasia. In addition, sucrase enzyme activity was determined in three sets of simultaneously harvested polyps, cancer, and adjacent normal mucosa from the same patient. All severely dysplastic polyps (6/6) exhibited SI staining. Most polyps (85%) with 3+ staining (i.e., greater than 10% of polyp positive for SI) had severe dysplasia, whereas those with mild dysplasia had either 1% to 5% staining or no staining in 95% of the cases. These data indicate that the extent of SI immunostaining in polyps correlates with the degree of dysplasia (p = 0.0001). Sucrase-isomaltase activity in the polyps was 18.1 +/- 1.8 mU/mg (mean +/- SD); in adjacent carcinoma SI activity was 29.1 +/- 1.8 mU/mg. Adjacent mucosa showed no activity in all cases. In summary, our results suggest that SI expression correlates with the progression of dysplastic adenomatous polyps to carcinoma. Sucrase-isomaltase expression may be useful as a clinical marker to improve our prognostic capabilities in patients with dysplastic lesions of the colon, that is, inflammatory bowel disease.