Differentiation-associated changes in mucin glycoprotein antigenicity in mucosa adjacent to rare gastrointestinal tract tumours of non-mucosal origin

Relationship between biological behavior and phenotypic expression in undifferentiated-type gastric carcinomas

BACKGROUND

It has been proved that some differentiated-type gastric carcinomas have a gastric phenotype. Similarly, it can be conjectured that some undifferentiated-type gastric carcinomas have an intestinal phenotype and that there are biological differences between undifferentiated-type gastric carcinomas with a gastric phenotype and those with an intestinal phenotype. We classified the phenotypes of early undifferentiated-type gastric carcinomas and investigated the relationship between their biological behavior and the phenotypes.

METHODS

Sixty lesions of intramucosal undifferentiated-type gastric carcinoma were classified into four phenotypes; gastric type, incomplete-intestinal type, complete-intestinal type, and unclassified type, according to the expression of CD10, MUC2, small-intestinal mucinous antigen (SIMA), human gastric mucin (HGM), or concanavalin A (ConA).

RESULTS

The incidence of gastric-type carcinoma, incomplete-intestinal-type carcinoma, and complete-intestinal-type carcinoma was 33% (20 cases), 65% (39 cases), and 2% (1 case), respectively. There was no significant difference in any of the clinicopathological factors examined between the 20 gastric-type carcinomas and the 40 intestinal-type carcinomas, but there were significant differences in the morphological findings. Intestinal-type carcinomas had a glandular structure more frequently than the gastric-type carcinomas. The spreading pattern of gastric-type carcinomas showed a middle-layer type more frequently than the intestinal-type carcinomas.

CONCLUSION

Undifferentiated-type gastric carcinomas frequently expressed an intestinal phenotype. There were differences in the growth patterns between undifferentiated-type gastric carcinomas with a gastric phenotype and those with the intestinal phenotype.

Differences in sialyl-Tn antigen expression between keratoacanthomas and cutaneous squamous cell carcinomas

Keratoacanthoma and squamous cell carcinoma are common skin tumors, especially in immunosuppressed transplant recipients, but the distinction between these two types of epidermal neoplasia may be difficult. Sialyl-Tn (Sia-GalNAc-O-Ser/Thr) is a cell surface carbohydrate associated with hyperplasia in squamous epithelium, and correlated with poor prognosis in several human adenocarcinomas. Twenty-seven keratoacanthomas and 29 cutaneous squamous cell carcinomas were examined for the expression of sialyl-Tn and of the Ki67 epitope, the latter a marker for cell proliferation. By immunohistochemistry, basaloid tumor cells at the periphery of tumor nests showed some degree of sialyl-Tn expression in 16 keratoacanthomas (59%), while only three squamous cell carcinomas (10%) showed sialyl-Tn-positive basaloid tumor cells (p<0.001). Keratinized, differentiated tumor cells were more often sialyl-Tn-positive in keratoacanthomas (89%) than in squamous cell carcinomas (31%) (p<0.001). A striking sialyl-Tn-positivity in the basal cell layer was found in a border zone directly adjacent to most tumors of both types (88 and 88%). By immunohistochemical examination of parallel sections and by double immunofluorescence, sialyl-Tn antigen expression was primarily seen in cells that did not express Ki67, although some overlap was present. Keratoacanthomas from transplant recipients did not differ in sialyl-Tn expression compared to those from non-immunosuppressed patients. The results indicate that sialyl-Tn expression is not directly related to cell proliferation, but rather to cellular features of post-mitotic cells, and that sialyl-Tn is not associated with a malignant phenotype. Sialyl-Tn may be linked to tumor regression, as seen in keratoacanthomas.

Mucin staining

Images

Distribution of sialosyl Tn and Tn antigens within normal and malignant colorectal epithelium

Expression of the core blood group structures sialosyl Tn (STn) and Tn is regarded as a colorectal cancer-specific change reflecting truncated synthesis of the oligosaccharide component of goblet cell mucin. The distribution of STn and Tn in normal and malignant epithelium has been studied in detail by a combination of mucin-, lectin-, and immunohistochemistry with and without pretreatment with potassium hydroxide (KOH), neuraminidase, and KOH-neuraminidase. When O-acetylated sialic acid (neuraminidase-resistant) is converted by saponification to non-O-acetylated sialic acid (neuraminidase-sensitive), normal colorectal goblet cells (mainly of the lower two-thirds of crypts) are immunoreactive with the monoclonal antibody TKH2 (specific for STn). This immunoreactivity is abolished by the interposition of neuraminidase, but goblet cells then become immunoreactive with Hb-Tn1 (specific for Tn). While colorectal cancer mucin expresses STn, expression of Tn is not seen in either goblet cell mucin or extracellular material showing the morphological and histochemical characteristics of secretory mucin. Tn expression in cancers is mainly limited to the Golgi zone and in a proportion of cases to cytoplasm and apical membrane (glycocalyx) of columnar cells and inspissated material within lumina. The material reacting with Hb-Tn1 may be upregulated, membrane-associated MUC1 glycoprotein rather than MUC2 or MUC4 goblet cell mucin. The presence of STn and cryptic Tn within normal colorectal goblet cells and the absence of Tn expression within colorectal cancer secretory mucin contradicts the generally accepted concept of cancer-specific incomplete glycoprotein synthesis within these neoplasms.

Prostaglandin E2 alters terminal glycosylation of high molecular weight glycoproteins, released by pig gastric mucous cells in vitro

The gastric mucus layer consists of high molecular weight glycoproteins (HMG). E-Type prostaglandins (PGs) stimulate total HMG release from isolated gastric mucous cells. We determined the effects of PGE2 on HMG glycosylation. Pig gastric mucous cells were cultured for 20 h with 1 mumol/l PGE2. Released HMG were isolated by gel chromatography and periodic acid-Schiff (PAS)-positive sugars and protein-bound [14C]GlcNAc were determined. Monosaccharides terminally linked to HMG oligosaccharide chains were monitored by lectin enzyme linked immunosorbent assay (ELISA): N-acetylglucosamine (GlcNAc) with Datura stramonium agglutinin, N-acetylgalactosamine (GalNAc) with soy bean agglutinin, fucose (Fuc) with Ulex europaeus I agglutinin and sialic acids (Sial) with Sambucus nigra agglutinin. PGE2 stimulated total HMG release, indicated by an increase of PAS-positive sugars to 170% and [14C]GlcNAc to 220% of controls. Terminal GlcNAc increased to 128%, GalNAc to 133%, Fuc to 165% and Sial to 182%. In addition to stimulation of total HMG release, PGE2 caused alterations of HMG glycosylation, which may modulate HMG viscosity and microbiological barrier function.

Is the carbohydrate sialosyl-Tn a marker for altered, non-malignant activity in squamous epithelium in the head and neck region?

Cell surface carbohydrates are involved in many cell functions such as cellular differentiation, adhesion, and invasion. A carbohydrate, sialosyl-Tn (STn), is expressed in many human carcinomas but generally not in normal epithelia. In the oral mucosa, however, STn has recently been observed on basal cells in some lesions with epithelial hyperplasia and dysplasia. The aim of this study was to carry out a systematic investigation of STn expression on epithelial basal cells in hyperplastic, 'borderline' malignant, and malignant head and neck lesions, to see if the expression of STn is associated specifically with hyperplastic conditions. Using the primary monoclonal antibody TKH2, normal controls did not reveal STn. STn was detected on probably post-mitotic basal cells in hyperplastic head and neck lesions and on basal cells adjacent to cancers, but not within the carcinomas. A Ki67 antibody reacted with basal cells in other locations. The most highly differentiated lesions, such as focal epithelial hyperplasia and verrucous hyperplasia, revealed a high percentage (86 per cent in both cases) of STn reactivity. The least-differentiated verrucous carcinomas (VCs) and keratoacanthomas (KAs) did not express STn, in contrast to the highly differentiated VCs and KAs. These findings indicate that STn-negative cases may have a greater malignant potential that the STn-positive cases. In conclusion, STn expressed on basal cells is possibly a marker for non-malignant conditions with altered basal cell activity and for highly differentiated verrucous carcinomas.

Colorectal mucin histochemistry in health and disease: a critical review

Neoplastic, inflammatory and regenerative processes affecting colorectal mucosa are associated with alterations in structure of epithelial mucin. This review collates mucin-, lectin-, and immuno-histochemical observations on colorectal mucins and introduces recent molecular genetic insights into the structure of the protein backbone of mucins. The numerous structural modifications uncovered by the various technical approaches have been reduced to a few manageable principles that are of relevance to both researcher and diagnostic pathologist. Particular attention is drawn to the need to appreciate the limited specificities of probes, the confounding influences of anatomical site and genetic factors (necessitating the use of appropriate positive and negative control tissues) and the precise location of secretory material. In the past, insufficient attention has been given to the effects of altered differentiation including metaplasia and differing lineage expression in epithelial disorders of growth. It is likely that certain changes loosely ascribed to goblet cell mucin, such as neo-expression of blood group antigens and anomalous expression of core carbohydrate structures, do not occur at all. Critical examination of available data point to only two consistent and unequivocal changes affecting goblet cell mucin in pathological processes: loss of O-acetyl substituents at sialic acid C4 and C7,8,9 and increased sialylation. Furthermore, there are no neoplasia-specific alterations in mucins documented to date. All neoplasia-associated changes have been described in non-neoplastic lesions also.

Dolichos biflorus agglutinin binding in hereditary bowel cancer

Dolichos biflorus agglutinin (DBA) binds specifically to N-acetylgalactosamine (GalNAc), one of the 5 sugars contributing to the oligosaccharide component of human colorectal goblet cell mucin. DBA binds to goblet cells of the upper crypt and surface epithelium within the proximal colon and to the majority of goblet cells of the distal large bowel. DBA therefore serves as a marker of colorectal goblet cell differentiation with a distinct proximal to distal gradient effect. Previous reports indicate significant loss of DBA reactivity within morphologically normal colorectal mucosa derived from at-risk members of hereditary non-polyposis colorectal cancer (HNPCC) families. This finding could not be confirmed in the present study. Reduced binding was a relatively consistent finding in transitional mucosa, hyperplastic polyps and carcinoma, with adenomas displaying a more varied pattern of loss. Reduced binding by DBA may be explained by several mechanisms and may not necessarily reflect loss of GalNAc. The concept that lectins can be used to identify stepwise changes that occur during neoplastic evolution should not be accepted uncritically.