Expression of a unique protein on colon cancer cells that reacts with a novel monoclonal antibody and ulcerative colitis serum

3'-sulfated LewisA/C: An oncofetal epitope associated with metaplastic and oncogenic plasticity of the gastrointestinal foregut

Metaplasia, dysplasia, and cancer arise from normal epithelia via a plastic cellular transformation, typically in the setting of chronic inflammation. Such transformations are the focus of numerous studies that strive to identify the changes in RNA/Protein expression that drive such plasticity along with the contributions from the mesenchyme and immune cells. However, despite being widely utilized clinically as biomarkers for such transitions, the role of glycosylation epitopes is understudied in this context. Here, we explore 3'-Sulfo-Lewis A/C, a clinically validated biomarker for high-risk metaplasia and cancer throughout the gastrointestinal foregut: esophagus, stomach, and pancreas. We discuss the clinical correlation of sulfomucin expression with metaplastic and oncogenic transformation, as well as its synthesis, intracellular and extracellular receptors and suggest potential roles for 3'-Sulfo-Lewis A/C in contributing to and maintaining these malignant cellular transformations.

The B-cell system in inflammatory bowel disease

Secretory immunity is the best-defined part ot the mucosal immune system. This adaptive humoral defense mechanism depends on a fine-tuned cooperation between secretory epithelia and local plasma cells. Such mucosal immunocytes produce preferentially dimers and larger polymers of immunoglobulin A (collectively called pIgA), which contain J chain and therefore can bind to the epithelial secretory component (SC). This transmembrane glycoprotein functions as pIg receptor (pIgR) that also translocates pentameric IgM to the epithelial surface. B cells with a high level of J-chain expression and pIg-pIgR interactions at mucosal effector sites are thus necessary for the generation of secretory antibodies (SIgA and SIgM). Secretory antibodies perform immune exclusion in a first-line defense, thereby counteracting microbial colonization and mucosal penetration of soluble antigens. However, local production of pIgA is significantly down-regulated in inflammatory bowel disease (IBD), as revealed by strikingly decreased J-chain expression. Although the total increase of the immunocyte population in IBD lesions probably compensates for the relatively reduced pIgA production, decreased pIgR/SC expression in regenerating and dysplastic epithelium signifies that the SIgA system is topically deficient. There is, moreover, a significant shift from IgA2 to IgA1 production, the latter subclass being less resistant to proteolytic degradation. These changes--together with activation of mucosal macrophages and a dramatic increase of IgG-producing cells--may reflect local establishment of a second defense line which, however, is unsuccessful in its attempt to eliminate antigens derived from the indigenous microbial flora. Such a 'frustrated' local humoral immune system results in altered immunological homeostasis and jeopardized mucosal integrity. Complement activation observed in relation to epithelium-bound IgG1 in ulcerative colitis indicates, moreover, that the surface epithelium is subjected to immunological attack by an autoimmune reaction. These luminal deposits regularly contain terminal cytotoxic complement, and often also C3b as a sign of persistent activation. Comparison of identical twins, discordant with regard to ulcerative colitis, suggests that the markedly skewed local IgG1 response seen in this IBD entity may be genetically determined. The initial event(s) eliciting B-cell driven immunopathology in IBD remains unknown. Abrogation of oral tolerance to certain antigens from commensal bacteria has been suggested as a putative early mechanism, and lymphoid neogenesis and hyperplasia in the lesions most likely signify massive microbial overstimulation of the local B-cell system. Such ectopic lymphoid microcompartments may contribute substantially to the proinflammatory systemic-type of B-cell responses occurring in established IBD lesions.

Utility of immunohistochemistry in distinguishing primary adenocarcinomas from metastatic breast carcinomas in the gastrointestinal tract

CONTEXT

Breast carcinoma often metastasizes to the gastrointestinal tract, especially the stomach, where it is frequently difficult to distinguish from a primary gastric carcinoma.

OBJECTIVE

To evaluate the utility of immunohistochemical stains in differentiating primary gastric carcinomas from metastatic breast carcinomas.

DESIGN

Mucosal biopsy specimens from 47 adenocarcinomas involving the gastrointestinal tract (28 primary gastric carcinomas and 19 metastatic breast carcinomas) and 16 control cases of primary breast carcinomas without metastasis were immunohistochemically stained for estrogen receptor protein (ER), progesterone receptor protein (PR), gross cystic disease fluid protein (GCDFP), human epidermal growth factor receptor 2 protein, cytokeratin (CK) 5/6, CK/7, CK/20, a panel of mucin glycoprotein antigens (MUC2, MUC3, MUC5AC, and MUC6), monoclonal antibody DAS-1, and caudal-type homeobox transcription factor CDX2 and compared between primary and metastatic adenocarcinomas.

RESULTS

Highly significant proportions of metastatic breast carcinomas were positive for ER (72%), PR (33%), GCDFP (78%), and CK5/6 (61%) compared with primary gastric carcinomas (ER, 0%; PR, 0%; GCDFP, 0%; and CK5/6, 14%) (P < .001, P = .002, P < .001, and P = .004, respectively). Of these immunostains, ER, PR, and GCDFP were 100% specific. Primary breast tumors and their metastases showed a similar phenotypic profile. In contrast, primary gastric carcinomas showed significantly higher proportions of cases that stained with CK20 (50%), MUC2 (54%), MUC5AC (71%), MUC6 (39%), DAS-1 (43%), and CDX2 (67%) compared with metastatic breast carcinomas (CK20, 0%; MUC2, 24%; MUC5AC, 6%; MUC6, 0%; DAS-1, 0%; and CDX2, 0%) (P = .001, P = .01, P < .001, P = .02, P = .009, and P < .001, respectively). No significant differences were observed with regard to any of the other immunostains (human epidermal growth factor receptor 2 protein, CK7, and MUC3) between the patient groups.

CONCLUSIONS

Estrogen receptor protein, PR, GCDFP, CK5/6, CK20, MUC5AC, MUC6, DAS-1, and CDX2 are helpful in distinguishing primary gastric carcinomas from metastatic breast carcinomas. Of these, ER, PR, and GCDFP are highly specific for metastatic breast carcinomas, whereas CK20, DAS-1, MUC2, MUC5AC, MUC6, and CDX2 are highly specific for primary gastric carcinomas.

Externalization of tropomyosin isoform 5 in colon epithelial cells

Ulcerative colitis (UC) is associated with autoantibody response to a cytoskeletal protein, human tropomyosin (hTM) isoform-5 (hTM5). Because hTM5 is an intracellular protein, it may remain inaccessible to the autoantibodies. Therefore, we have investigated the possibility of externalization of hTM5 in colon epithelial cells. Freshly isolated colonic and small intestinal epithelial cells and LS-180 colon cancer cell line were examined for surface expression of hTM5 by flow cytometric analysis using hTM isoform-specific MoAbs. The extracellular release of hTM5 was determined by Western blot and radioimmunoprecipitation analyses. Physical association of hTM5 with a membrane-associated colon epithelial protein (CEP) was examined by co-immunoprecipitation of hTM5 with anti-CEP MoAb, and CEP with anti-hTM5 MoAb. Cell surface expression of hTM5 was observed in colonic epithelial and LS-180 cells but not in small intestinal epithelial cells. LS-180 cells spontaneously released hTM5 as well as CEP into the culture medium that was significantly stimulated by a calcium ionophore, A23187, but inhibited by phorbol-12-myristate-13-acetate, monensin and methylamine. Co-immunoprecipitation experiments revealed that hTM5 forms a complex with CEP. We conclude that hTM5 is externalized in colon but not in small intestinal epithelial cells. The physical association of hTM5 with CEP suggests a possible chaperone function of CEP in the transport of hTM5, a putative target autoantigen in UC.

Relationship of extraintestinal involvements in inflammatory bowel disease: new insights into autoimmune pathogenesis

Extraintestinal manifestations in patients with inflammatory bowel disease (IBD) are quite common (about 25%) and careful clinical observation and statistical analysis during the last five decades have demonstrated that in colitis-associated extraintestinal complications, the organs most commonly involved are the biliary tract, joints, skin, and eyes. However, almost all organs can be involved in IBD. Some of the extraintestinal manifestations may precede IBD, although the majority accompany the underlying disease and are influenced by its activity. Prompt recognition of extracolonic organ involvement in IBD is important because of the relative refractoriness of the disease and a possible increase in morbidity and mortality. The identified pathogenetic autoimmune mechanisms include genetic susceptibility, cytokine imbalances, antigenic display of autoantigen, aberrant self-recognition, and immunopathogenetic autoantibodies against organ-specific cellular antigen(s) shared by colon and extracolonic organs. Microbes may play an important role, probably by molecular mimicry.