Previous studies have suggested that abnormal expression of enzymes characteristic of the intestinal brush border might accompany colonic neoplasia and possibly facilitate identification of epithelium at risk of malignancy. To test this possibility, the distribution of the brush border enzymes sucrase‐isomaltase (SIM), maltase‐glucoamylase (MGA), aminopeptidase‐N (APN) and diaminopeptidylpeptidase‐IV (DPPIV) were studied by the immunoperoxidase method in biopsies from the rectum and caecum of normal subjects, and neoplastic and non‐neoplastic tissues from patients with adenoma or cancer. Brush border enzymes were detected by immunohistochemistry more frequently in the caecum than the rectum (P < 0.05) of normal subjects. Diaminopeptidylpeptidase‐IV and APN were present in highest concentration at the brush border of the most mature colonocytes on the luminal surface with less staining in the crypt, whereas SIM and MGA staining of the brush border was as prominent on crypt cells as surface cells. While all cancers expressed at least one enzyme, there was heterogeneity of staining within tumours and a tendency to lose polarity of enzyme expression in cells, sometimes with dense staining of the cytoplasm. Distally situated adenomas uncommonly expressed a brush border enzyme (25%) and the only enzyme expressed in them was SIM. These findings indicate that these brush border enzymes are not exclusively expressed in the small intestine; DPPIV and APN are markers of the normal mature colonocyte and should prove useful as markers of differentiation. However, the changes associated with neoplasia would not appear to be of clinically predictive value. The low expression in adenomas suggests a block in the differentiation process early in tumourigenesis, whereas the patchy re‐expression, accompanied by a loss of cellular polarity in cancers, suggests derepression of gene expression for these enzymes.
|Number of pages||8|
|Journal||Journal of Gastroenterology and Hepatology|
|Publication status||Published - Aug 1992|
- brush border
- large bowel cancer.