Gastric proteases in Barrett's esophagus

Global changes in gene expression of Barrett's esophagus compared to normal squamous esophagus and gastric cardia tissues

BACKGROUND

Barrett's esophagus (BE) is a metaplastic precursor lesion of esophageal adenocarcinoma (EA), the most rapidly increasing cancer in western societies. While the prevalence of BE is increasing, the vast majority of EA occurs in patients with undiagnosed BE. Thus, we sought to identify genes that are altered in BE compared to the normal mucosa of the esophagus, and which may be potential biomarkers for the development or diagnosis of BE.

DESIGN

We performed gene expression analysis using HG-U133A Affymetrix chips on fresh frozen tissue samples of Barrett's metaplasia and matched normal mucosa from squamous esophagus (NE) and gastric cardia (NC) in 40 BE patients.

RESULTS

Using a cut off of 2-fold and P<1.12E-06 (0.05 with Bonferroni correction), we identified 1324 differentially-expressed genes comparing BE vs NE and 649 differentially-expressed genes comparing BE vs NC. Except for individual genes such as the SOXs and PROM1 that were dysregulated only in BE vs NE, we found a subset of genes (n = 205) whose expression was significantly altered in both BE vs NE and BE vs NC. These genes were overrepresented in different pathways, including TGF-β and Notch.

CONCLUSION

Our findings provide additional data on the global transcriptome in BE tissues compared to matched NE and NC tissues which should promote further understanding of the functions and regulatory mechanisms of genes involved in BE development, as well as insight into novel genes that may be useful as potential biomarkers for the diagnosis of BE in the future.

The molecular biology of esophageal and gastric cancer and their precursors: oncogenes, tumor suppressor genes, and growth factors

The evolution of sequential histological changes from normal cells through invasive cancer affords the cancer biologist the opportunity to identify separate molecular steps involved in cancer progression. As one studies the development of human carcinoma, it becomes apparent that multiple genetic alterations affecting both cellular proto-oncogenes and tumor suppressor genes are involved during the development and progression of both esophageal and gastric cancers. The different histological forms of both esophageal and gastric carcinomas as well as their differing etiologies result in the possibility that a spectrum of genetic changes is involved in different tumor types. p53 abnormalities occur frequently in tumors arising in both organs, and in both sites p53 abnormalities can be observed in precancerous lesions as well as in overt cancer. Subsequent abnormalities affecting other genes (eg, epithelial growth factor receptors [EGFRs]) potentially enhance the growth potential of tumors. This review focuses on abnormalities of oncogenes, tumor suppressor genes, and growth factors commonly found in cancers of the esophagus and stomach.

Histogenetical investigations on adenocarcinomas of the esophagogastric junction. An immunohistochemical study

The presence of Pepsinogen II (PG II), gastral mucin (2B5), CA 19-9, BW 494 and Cytokeratin 20 (CK 20) was investigated in 69 adenocarcinomas of the esophagogastric junction (15 carcinomas in Barrett's esophagus, 9 distal esophageal carcinomas, 31 carcinomas of the cardia and 14 subcardial carcinomas). Evidence of gastric differentiation (expression of Pepsinogen II and/or gastric mucin) was found in more than 50% of the Barrett's carcinomas and the carcinomas of the cardia, but only in 20% of the subcardial carcinomas. High rates of antigen expression were found for the "intestinal" markers CA 19-9 (between 55.5% and 100%) and BW 494 (between 42.9 and 86.7%). CK-20 expression was detected to a significantly higher degree in Barrett's carcinomas (73.3%) than in the other groups (between 29% and 44.4%). These data indicate that the distribution of adenocarcinomas with gastric and/or intestinal differentiation at the esophagogastric junction forms a continuum without clear-cut borders.

Distinct immunohistochemical findings in columnar epithelium of esophageal inlet patch and of Barrett's esophagus

Immunohistochemistry was performed on biopsies of columnar mucosa from 11 patients with Barrett's esophagus and 11 patients with columnar mucosa in the cranial esophagus, the "inlet patch." Both epithelia contained endocrine cells, immunoreactive to antisera against serotonin, glucagon, somatostatin, and pancreatic polypeptide; the specialized mucosa of Barrett's esophagus contained, in addition, neurotensin-immunoreactive cells, and in the mucosa of an inlet patch we found a gastrin cell. These findings are not compatible with some of the current theories on the origin of these epithelia. The mucosa of the inlet patch has been considered to consist of heterotopic gastric mucosa. The mucosa of the adult human stomach, however, does not contain glucagon cells. These cells are only present in the early embryonic stomach, and they disappear during embryonogenesis. According to our findings, the mucosa of the inlet patch therefore represents embryonic gastric mucosa. The specialized columnar epithelium of Barrett's esophagus has been considered to have evolved from gastric mucous neck cells. However, although glucagon cells are a feature of the embryonic stomach, neurotensin-immunoreactive cells have not been found in the gastric mucosa. Our study suggests that the specialized columnar epithelium of Barrett's esophagus originates from a very immature multipotent gastrointestinal stem cell.

Human pepsinogen C (progastricsin) polymorphism: evidence for a single locus located at 6p21.1-pter

A series of six clones containing the entire human pepsinogen C gene (PGC) was identified in a cosmid vector library by using cDNA and oligonucleotide probes. The 10.7-kb PGC gene includes nine exons and exhibits a high degree of sequence identity (60%) with the functionally related pepsinogen A genes. The predicted amino acid sequence was identical with the partial amino-terminal and carboxyl-terminal sequences of purified pepsinogen C. An informative restriction fragment length polymorphism was detected with several restriction enzymes and involved an insertion or deletion of 100 bp of intron sequence located between exons 7 and 8. Evidence that there is only a single PGC gene in humans is presented. The PGC gene and the prolactin gene were regionally localized to 6p21.1-pter by analysis of mouse X human somatic cell hybrids.

Differential expression of pepsinogen isozymogens in a patient with Barrett esophagus

The pepsinogen A (PGA) isozymogens in the gastric mucosa and Barrett epithelium of a female patient with Barrett esophagus were studied on different occasions during a 3-year period by electrophoretic analysis of in vivo steady-state pepsinogen in biopsies by activity staining in combination with variant specific monoclonal antibodies and of de novo synthesized pepsinogen by autoradiography. In Barrett epithelium only one (Pg3) or two (Pg3 and Pg5) primary PGA gene products were detected, whereas in gastric mucosal biopsies three (Pg3, Pg4 and Pg5) primary gene products were demonstrated on all occasions. These differences strongly suggest differential expression/activation of individual gene numbers in the PGA gene cluster in Barrett esophagus and are in line with the preneoplastic nature of this condition. The mechanism behind this deregulation is currently under investigation by cell biology and molecular genetic techniques.