MUC4 is increased in high grade intraepithelial neoplasia in Barrett's oesophagus and is associated with a proapoptotic Bax to Bcl-2 ratio.

BACKGROUND: Patients with Barrett's oesophagus (BO) are at risk of oesophageal adenocarcinoma. Because the pattern of mucosal mucins changes during neoplastic progression, it may serve as a marker of intraepithelial neoplasia. AIMS: To determine the expression pattern of mucins in neoplastic BO epithelium (high grade dysplasia) and correlate it with the expression of apoptosis markers Bax and Bcl-2. METHODS: Thirty seven patients with BO were studied: 16 without intraepithelial neoplasia, six with high grade intraepithelial neoplasia (HGN), and 15 with infiltrating adenocarcinoma. Biopsies were obtained from squamous epithelium, Barrett's epithelium, and (when present) foci of suspected HGN or adenocarcinoma. MUC1-4, MUC5AC, MUC5B, MUC6, Bax, and Bcl-2 mRNA were determined by semiquantitative RT-PCR. MUC2, MUC5AC, and MUC6 protein was determined by immunoblotting. RESULTS: Mucin expression varied between neoplastic progression stages in BO. Mucin mRNA levels were low in squamous epithelium, except for MUC4, and were at least four times higher in BO and HGN (p<0.001), but less so in adenocarcinoma. MUC4 expression was significantly lower in BO than in normal squamous epithelium, whereas in HGN and adenocarcinoma, levels were significantly higher than in BO (p = 0.037). The Bax:Bcl-2 ratio was increased in HGN compared with BO (p = 0.04). MUC2, MUC5AC, and MUC6 protein values correlated with mRNA data. CONCLUSIONS: Mucin expression varies during the development of oesophageal adenocarcinoma in BO. MUC4 could serve as a tumour marker in this process. In contrast to animal studies, upregulation of MUC4 in HGN is associated with increased apoptosis, suggesting that MUC4 plays a minor role in apoptosis regulation in BO.

Rotavirus enterotoxin NSP4 binds to the extracellular matrix proteins laminin-beta3 and fibronectin.

Rotavirus is the most important cause of viral gastroenteritis and dehydrating diarrhea in young children. Rotavirus nonstructural protein 4 (NSP4) is an enterotoxin that was identified as an important agent in symptomatic rotavirus infection. To identify cellular proteins that interact with NSP4, a two-hybrid technique with Saccharomyces cerevisiae was used. NSP4 cDNA, derived from the human rotavirus strain Wa, was cloned into the yeast shuttle vector pGBKT7. An intestinal cDNA library derived from Caco-2 cells cloned into the yeast shuttle vector pGAD10 was screened for proteins that interact with NSP4. Protein interactions were confirmed in vivo by coimmunoprecipitation and immunohistochemical colocalization. After two-hybrid library screening, we repeatedly isolated cDNAs encoding the extracellular matrix (ECM) protein laminin-beta3 (amino acids [aa] 274 to 878) and a cDNA encoding the ECM protein fibronectin (aa 1755 to 1884). Using deletion mutants of NSP4, we mapped the region of interaction with the ECM proteins between aa 87 and 145. Deletion analysis of laminin-beta3 indicated that the region comprising aa 726 to 875 of laminin-beta3 interacts with NSP4. Interaction of NSP4 with either laminin-beta3 or fibronectin was confirmed by coimmunoprecipitation. NSP4 was present in infected enterocytes and in the basement membrane (BM) of infected neonatal mice and colocalized with laminin-beta3, indicating a physiological interaction. In conclusion, two-hybrid screening with NSP4 yielded two potential target proteins, laminin-beta3 and fibronectin, interacting with the enterotoxin NSP4. The release of NSP4 from the basal side of infected epithelial cells and the subsequent binding to ECM proteins localized at the BM may signify a new mechanism by which rotavirus disease is established.

Gastric-type mucin and TFF-peptide expression in Barrett's oesophagus is disturbed during increased expression of MUC2.

AIMS: Barrett's oesophagus constitutes metaplastic epithelium, often diagnosed by mucin histochemistry. We determined the mucins and trefoil factor family (TFF)-peptides that were expressed in Barrett's oesophagus, in order to study changes in protein expression in early stages of Barrett's oesophagus development. METHODS AND RESULTS: Biopsy specimens of 71 Barrett's oesophagus patients were collected, and sections were stained for secretory mucins by histochemistry. Immunohistochemistry was performed for secretory mucins (MUC2, MUC5AC, MUC5B, MUC6), TFFs (TFF1, TFF2, TFF3), and proliferation (Ki67). Protein expression in the tissue was measured semiquantitatively. MUC5AC and TFF1 showed high levels and strong colocalization in the surface epithelium, whereas MUC6, MUC5B and TFF3 were found in the deeper glandular structures. TFF2 was found in both surface and glandular epithelium. The co-ordinate expression patterns of these six markers were similar to gastric antrum epithelium. MUC2 expression was ubiquitously associated with goblet cells within intestinal metaplasia, occurring in 68% of patients, and was correlated with increasing proliferation in the epithelium. CONCLUSIONS: Virtually all cells in Barrett's oesophagus epithelium displayed a secretory phenotype, demonstrating a co-ordinate gastric-type MUC and TFF expression. When MUC2 expression was more pronounced, the expression patterns of the other MUCs and the TFFs were increasingly disturbed. MUC2 expression may constitute a marker for early change in the phenotype of Barrett's oesophagus as a precancerous lesion.