Claudin expression in gastric adenocarcinomas: a tissue microarray study with prognostic correlation.

The claudins comprise a multigene family of integral membrane proteins, which play a major role in tight junction formation. Aberrations in the expression of certain claudins have been described in a number of malignancies. Our aims were to determine the expression pattern of claudins 1, 3, and 4 as well as ZO-1 in a large series of US patients with gastric cancer and to correlate expression with clinicopathologic and prognostic variables. Tissue microarrays were created from paraffinized samples from 146 patients with distal gastric adenocarcinomas (61 intestinal and 85 diffuse or mixed subtypes). In addition, cores of normal mucosa and intestinal metaplasia were taken from most cases. The microarrays were stained for claudins 1, 3, and 4 and ZO-1, and the intensity of staining was determined using a 3-point scale. Moderate claudin 1 and ZO-1 membranous staining were present, whereas only focal weak claudin 3 and 4 membranous staining was present in normal gastric epithelium. Moderate to strong staining of claudins 1, 3, 4, and ZO-1 was detected in 74%, 48%, 62%, and 74% of the intestinal but in only 46%, 24%, 45%, and 36% of the diffuse subtype of adenocarcinomas (P < .05). Cox multivariate analysis revealed that tumor stage, diffuse subtype, and moderate to strong claudin 4 staining were associated with decreased survival (P < .02). In conclusion, claudins 1, 3, and 4 and ZO-1 are strongly expressed in most gastric intestinal-type adenocarcinomas but less frequently in diffuse gastric cancers. The up-regulation of claudin expression during gastric carcinogenesis suggests their potential utility as diagnostic biomarkers and possible targets for therapeutic intervention.

Identification of a novel protein, LYRIC, localized to tight junctions of polarized epithelial cells.

Tight junctions (TJ) are multiprotein complexes that function to regulate paracellular transport of molecules through epithelial and endothelial cell layers. Many new tight junction-associated proteins have been identified in the past few years, and their functional roles and interactions have just begun to be elucidated. In this paper, we describe a novel protein LYsine-RIch CEACAM1 co-isolated (LYRIC) that is widely expressed and highly conserved between species. LYRIC has no conserved domains that would indicate function and does not appear to be a member of a larger protein family. Data from analysis of rat and human tissue sections and cell lines show that LYRIC colocalizes with tight junction proteins ZO-1 and occludin in polarized epithelial cells, suggesting that LYRIC is part of the tight junction complex. LYRIC dissociates from ZO-1 when junctional complexes are disrupted, and as tight junctions reform, ZO-1 relocalizes before LYRIC. These results suggest that LYRIC is most likely not a structural component required for TJ formation, but rather is recruited during the maturation of the tight junction complex.

Two variable regions in carcinoembryonic antigen-related cell adhesion molecule1 N-terminal domains located in or next to monoclonal antibody and adhesion epitopes show evidence of recombination in rat but not in human.

In this paper, we have characterized the structure, evolutionary origin, and function of rat and human carcinoembryonic antigen-related cell adhesion molecule1 (CEACAM1) multifunctional Ig-like cell adhesion proteins that are expressed by many epithelial tissues. Restriction enzyme digestion reverse transcriptase-PCR analysis identified three cDNAs encoding novel CEACAM1 N-domains. Comparative sequence analysis showed that human and rat CEACAM1 N-domains segregated into two groups differing in similarity to rat CEACAM1(a)-4L and human CEACAM1. Sequence variability analysis indicated that both human and rat N-domains possessed two variable regions, and one contained a major adhesive epitope. Recombination analysis showed that the group of rat but not human N-domains with high sequence similarity was derived at least in part by recombination. Binding assays revealed that three monoclonal antibodies with strong reactivity for the CEACAM1(a)-4L N-domain showed no reactivity with CEACAM1(b)-4S, an allele with a different N-domain sequence. CEACAM1(b)-4S displayed adhesive activity efficiently blocked by a synthetic peptide corresponding to the adhesive epitope in CEACAM1(a)-4L. Blocking analysis also showed that the adhesive epitope for rat CEACAM1 was located downstream from the equivalent human and mouse epitopes. Glycosylation analysis demonstrated O-linked sugars on rat CEACAM1(b)-4S from COS-1 cells. However, this was not the alteration responsible for the lack of monoclonal antibody reactivity. When considered together with previous studies, our findings suggest an inverse relationship between functionality and amino acid sequence similarity to CEACAM1. Like IgG, the N-domain of CEACAM1 appears to tolerate 10-15% sequence diversification without loss of function but begins to show either altered specificity or diminished functionality at higher levels.