Sucrase‐isomaltase expression and enterocytic ultrastructure of human colorectal tumors

Abstract

We report the relative frequency of sucrase-isomaltase (SI) antigen expression in human colonic adenocarcinoma (22/57), in peritumoral mucosa taken next to the tumor (31/41) or distant from it (29/42) as well as in 21/23 polyps. Our results are based on indirect immunofluorescence with a monoclonal antibody (MAb) specific for human intestinal SI. A regular and intense expression of SI occurred only in 6 tumor specimens. In the remaining 16 SI-positive tumor samples, labelling was heterogeneous, i.e., scattered over more or less extensive areas. A similar irregular staining pattern was also found in polyps and in peritumoral mucosa, irrespective of its distance from the tumor. Electron microscopic examination of 19 carcinomas mostly revealed altered brush-border membrane features, irrespective of histological SI staining pattern. Brush-border enzyme activities of sucrase, alkaline phosphatase and maltase showed no difference between tumor specimens and peritumoral mucosa, but aminopeptidase was depressed in the former. Sucrase activity was extremely low (mean values 1.1 to 1.8 mU/mg protein) and rose only exceptionally to 17.5 mU/mg prot.

Expression of Human Intestinal mRNA Transcripts during Development: Analysis by a Semiquantitative RNA Polymerase Chain Reaction Method

“…These same samples showed virtually undetectable sucrase activity (Rousset M, Zweibaum A, unpublished data). Although there is now general agreement that sucrase-isomaltase is expressed at low levels in normal adult colon (26,27,32,44,45), there is clearly substantially less protein and enzyme activity than in the small intestine and than might have been expected from the levels of mRNA that we have observed in this study. High levels of expression of the sucrase-isomaltase protein in fetal colon between 8 and 30 wk of gestation are well documented (28,(31)(32)(33), and this is consistent with the high mRNA levels observed here.…”

A Novel Colonic Repressor Element Regulates Intestinal Gene Expression by Interacting with Cux/CDP

“…Similar transient expression of SI, as well as other intestinal brush border enzymes, has also been observed in the human fetal colon (48). It has been suggested that the mechanisms directing transient SI expression in the colon are recapitulated in the process of human colonic neoplasia, with the reexpression of SI in the majority of colonic adenomatous polyps and adenocarcinomas (4,9,45). A comparable recurrence of SI expression was also found in rodent colon tissues subjected to oncogene-mediated transformations (29).…”

“…SI expression is tightly regulated during postnatal development and becomes strongly induced in the small intestine at the transition from suckling to weaning (40). SI reexpression in the colonic epithelium is also observed under certain circumstances such as colonic neoplasia (4,9,45). Our study has undertaken the functional characterization of a novel colonic repressor element of the SI promoter (CRESIP) in the intestinal epithelium.…”

Expression of sucrase and intestinal-type alkaline phosphatase in colorectal carcinoms in rats treated with methylazoxymethanol acetate

“…Strong expressions of sucrase (Zweibaum et al 1983Wiltz et al 1990;Gorvel et al 1991) and sucrase and ALP (Celano et al 1993) have also been observed in some dierentiated human colon cancers and derived cell lines. While one investigation found no dierences in the striated-cell-border activities of sucrase, ALP and maltase between colorectal tumors and peritumoral mucosa (Czernichow et al 1989) and I-ALP activity was contained in normal small-intestinal mucosa, another report found only moderate elevation of I-ALP activity in colon cancers (Harmenberg et al 1991). The cellular heterogeneity of adenocarcinomas with multiple subpopulations of cells with dierent properties might explain this controversy (Arends et al 1985).…”