A comparison of membrane enzymes of human and pig oesophagus; the pig oesophagus is a good model for studies of the gullet in man

The distribution and relative catalytic activities of five plasma membrane enzymes (alkaline phosphatase, dipeptidyl peptidase IV, gamma-glutamyl transpeptidase, microsomal alanyl aminopeptidase and glutamyl aminopeptidase) were examined in human and pig oesophagus. In both species, alkaline phosphatase activity occurred in basal and suprabasal cells of the epithelium and in capillaries. Stromal cells in the human submucosa were particularly reactive. Dipeptidyl peptidase IV was present in blood vessels and capillaries in man and pig and in submucous glands in the pig. The enzyme was also present in both species in the lamina propria cells immediately adjacent to the epithelial basal lamina. In the human, gamma-glutamyl transpeptidase occurred in the epithelial basal cells and in isolated basal and lower prickle cells in the pig. Stromal cells in the human submucosa were strongly reactive and capillaries in the muscularis propria in both species moderately active. Microsomal alanyl aminopeptidase was detected in lamina propria cells adjacent to the epithelial basal cell layer in man and pig and at the apices of mucous cells in pig submucous glands. Weak glutamyl aminopeptidase activity was confined to capillaries in both species. The findings of this study, along with the ready availability of pig oesophagus, suggest that the pig may be a suitable model for studies of the gullet in man.

Oesophageal defence mechanisms

Various defence mechanisms are found in the oesophagus which can be elicited by reflux damage. Premucosal defence includes bicarbonate ions and epidermal growth factor (EGF) secreted by salivary and oesophageal glands. The mucosa can respond by increasing epithelial cell turnover and upregulating EGF receptor and endocytosis. The intercellular barrier can be increased by the contents of membrane-coating granules. Local pH can be regulated by carbonic anhydrase. The whole viscus can exhibit peristalsis to effect a mechanical clearance of the refluxed gastric and duodenal material.

Regulation of cell number in the mammalian gastrointestinal tract: the importance of apoptosis

The regulation of cell number in adult tissues is determined by the balance of cell production and cell loss. In the gastrointestinal tract, where there are well defined zones of proliferation and migration of both epithelial cells and associated fibroblasts, it is widely held that cell loss occurs by shedding into the gut lumen. Since the evidence for this is not compelling, we investigated the distribution and amount of apoptosis in the normal mammalian gut. In the stomach, small intestine and colon of rodents and man, there is a small number of apoptotic bodies in the epithelium and in the immediate sub-epithelial connective tissue. Engulfment by adjacent epithelial cells and sub-epithelial macrophages accounts for the removal of apoptotic bodies. Apoptotic bodies are not randomly distributed but are found towards the distal end of the known cellular migration routes of both epithelial and mesenchymal cells. Furthermore, consideration of the absolute numbers of apoptotic bodies, their rapid clearance and the dimensions of the small intestinal villi and colonic crypts indicates that the cell loss in the normal murine intestine can largely be explained on the basis of the observed apoptosis. Despite being inconspicuous in histological material, apoptosis probably accounts for the bulk of cell loss in the gut and is a central feature of the regulation of cell number in adult tissues.

Cell adhesion molecules in oesophageal epithelium

The distribution of a range of integrins, E-cadherin, and carcino-embryonic antigen (CEA) like molecules in normal human oesophageal epithelium was investigated immunohistochemically on frozen sections of endoscopic biopsy specimens. The integrin subunits alpha 2, alpha 3, alpha 6, alpha v, beta 1, and beta 5 were expressed throughout the epithelium. There was strong expression of alpha 2, alpha 3, and beta 1 subunits in the basal cell layer and for all the subunits studied the intensity of the staining decreased as cells moved towards the lumen. The heterodimer alpha v beta 3 was expressed weakly in the basal aspect of the basal cell layer only. The CEA molecules were not present in the basal cells layer but there was weak expression in the prickle cell layer and strong positivity in the mature functional layer. E-cadherin was found throughout the epithelium but was weakly expressed at the basal aspect of the basal cells layer and showed strong positivity in the prickle cell and squamous cell layers. These results indicate that cell-cell (E-cadherin, CEA) and cell-matrix (integrins) adhesion molecules show a well defined spatial pattern of immunoreactivity in the oesophageal mucosa and may play a part in the maintenance of normal tissue architecture and physiological homeostasis.

The prognostic significance of the accumulation of p53 tumour-suppressor gene protein in gastric adenocarcinoma

We have studied the expression of p53 in 206 patients with gastric adenocarcinomas. A standard immunohistochemical technique employing the CM-1 anti-p53 polyclonal antibody was applied to the routinely fixed and paraffin-embedded material from these tumours; overexpression of p53 was defined as positive nuclear staining: 46% (94/206) of gastric carcinomas expressed high levels of p53. There was no significant correlation between p53 positivity and the tumour grade, growth pattern, the Lauren type or lymph node metastases. Correlation with disease stage was only marginally significant (P = 0.05). Life table analysis revealed a highly significant association between p53 expression and survival (P = 0.0062), the odds ratio of death being 1.89 (95% confidence interval 1.33-2.69). The overall 5-year survival of patients with p53-positive tumours was 3% compared with 16% for those with p53-negative tumours (median survival time being 5.6 and 11.4 months respectively). These data suggest that overexpression of the p53 oncoprotein is an independent marker of shortened survival in gastric cancer patients.

Secretory and absorptive activity of oesophageal epithelium: evidence of circulating mucosubstances

The space between the oesophageal basal and prickle epithelial cells appears empty by standard ultrastructural preparative techniques. Fixation of human oesophageal biopsies with a variety of agents, including tannic acid, glutaraldehyde-lysine, cetylpyridinium chloride and Ruthenium Red shows that this space is filled with mucosubstances, some free, some attached to the cells as a glycocalyx. There is evidence that this material is secreted constitutively by the basal and prickle cells. This secretion may be changed or blocked by incubating oesophageal biopsies in the presence of colchicine or dinitrophenol. Incubation at 16 degrees C has the same effect. Absorption from the intercellular space may be followed using the fluid phase marker, horseradish peroxidase. Early endosomes may also be shown by their acid phosphatase activity. Incubation of biopsies at 20-22 degrees C allows early endosomes to accumulate material, but not pass it on the late endosomes.

Enzyme-linked immunosorbent assay for p53 in gastrointestinal malignancy: comparison with immunohistochemistry

Mutations in the p53 nuclear oncogene occur frequently in a wide spectrum of human malignancies and the mutant protein may prove to be a useful diagnostic or prognostic marker. It can be detected in fixed tissues by immunohistochemistry, but the type of fixative and conditions of fixation used can introduce variability. For routine clinical use, a method of analysis which is more easily standardized would, therefore, be of benefit. A two-site enzyme-linked immunosorbent assay (ELISA) was used to measure the level of p53 protein in soluble extracts from 20 gastrointestinal cancers (11 colonic, nine gastric). Immunohistochemistry was also performed on the paraffin-embedded sections of these tumours and the results of the two assays were compared. ELISA detected p53 at various levels in 10 cases, all of which were also positive by immunohistochemistry. Of the other 10, eight were immunohistochemically negative but two were positive. When the immunohistochemically positive specimens were ranked by scoring the degree of staining, there was a highly significant correlation with the quantitative ELISA results. Our study shows that the ELISA is sensitive and highly specific. It offers an alternative and simple method of assessing the p53 status in human tissues.

Monoclonal antibodies to cytoskeletal proteins: an immunohistochemical investigation of human colon cancer

Monoclonal antibodies raised to a number of microfilament-associated proteins were shown to recognize the appropriate proteins in extracts from human colon tissue. They were then used in an immunohistochemical study of normal colonic mucosa, adenomas, and adenocarcinomas. A strong reaction was seen in stromal cells within the tumours (both adenomas and adenocarcinomas) when frozen sections were stained with antibodies to filamin and caldesmon. In addition, a similar reaction was seen in the adenocarcinomas when stained with antibodies to talin and gelsolin. We believe that immunohistochemical staining with these antibodies reveals a tumour-induced process in the surrounding cells, possibly related to a host response to tumours.

Expression of p53 protein in normal, dysplastic, and malignant gastric mucosa: an immunohistochemical study

Mutations in the p53 nuclear oncogene are the most frequent genetic abnormalities encountered in human malignancies. Using the polyclonal antibody CM-1, we have examined the expression of the p53 oncoprotein immunohistochemically in archival material of normal, dysplastic, and malignant gastric mucosa. Abnormal expression of this protein was not observed in biopsies of normal gastric tissue (n = 30) but was detected in 22 of the 36 gastric cancers analysed (61 per cent). Nuclear staining was diffuse in 15 of the positive cancer cases, the remaining seven showing a more varied heterogeneous staining pattern. Abnormal p53 protein was not detected in mild (n = 14) or moderate (n = 16) gastric dysplasia but was present in 3 out of 15 severe dysplasia cases. The results suggest that expression of the p53 oncoprotein is a common finding in gastric cancer and occurs as a late event in the malignant transformation process.

Departmental audit in histopathology

Audit is now part of any laboratory service. Histopathology is no exception, and we have set up a system which allows us to review 4% of our specimens. These specimens are identified using a random number generator and reviewed by a consultant pathologist. Both slides and wet specimens are reviewed and graded according to a set scheme. The results from the first year of operation (1990) show a high rate of accuracy with no serious diagnostic disagreements between the auditor and the reporting pathologist. However, some errors which we would wish to prevent were detected and the audit has allowed us to take corrective measures. In our opinion, this form of audit is useful and necessary to maintain good clinical practice. The cost is considerable--histopathology is by its nature labour intensive. Recognition of this fact by health boards is essential if such systems are to continue.

Hyperplastic polyps: a cell lineage which both synthesizes and secretes trefoil-peptides and has phenotypic similarity with the ulcer-associated cell lineage

Hyperplastic polyps are common benign lesions of uncertain histogenesis, which occur in the colon in populations at risk for colorectal carcinoma. They contain neutral/MUC1 gene-related mucin which in turn is closely associated with the trefoil-peptide pS2, a major component of the ulcer-associated cell lineage, previously termed pseudopyloric metaplasia. We have examined 17 hyperplastic polyps for expression of the trefoil-peptides pS2 and human spasmolytic polypeptide by in situ hybridization and immunohistochemistry, as well as by using antisera to epidermal growth factor/urogastrone and its receptor and to epitopes of the product of the MUC1 gene to characterize any further similarity between these lesions and the ulcer-associated cell lineage and thus help elucidate the nature of the lesions. Our investigations show both human spasmolytic polypeptide and pS2 messenger RNA within the polyps, whereas only pS2 peptide could be demonstrated immunohistochemically. Epidermal growth factor/urogastrone, its receptor, and antisera to the MUC1 gene also showed widespread staining of these polyps. We suggest that hyperplastic polyps are formed of a lineage that both synthesizes and secretes trefoil-peptides and the MUC1 mucin and that hyperplastic polyps may be related to the phenotypically similar ulceration-associated cell lineage.

Increased expression of epidermal growth factor receptors in Barrett's esophagus associated with alkaline reflux: a putative model for carcinogenesis

A 49-yr-old male was reviewed who had a 10-yr history of reflux esophagitis. He presented initially with frequent heartburn of moderate severity and, on subsequent endoscopy, was noted to have erosive esophagitis and, at that time, a high maximal gastric acid output. During the next 5 yr, his symptoms and acid output diminished. Eight years after presentation, he was noted to have developed a small area of Barrett's metaplasia, without dysplastic change. Ten years after the initial presentation he was completely asymptomatic, despite having extensive Barrett's metaplasia, now with high grade dysplasia. As a result, he was referred for esophagogastrectomy. At the time of surgery, he had alkaline reflux, with antacid gastric contents and, subsequently, hypochlorhydria was proven by a pentagastrin test. A second individual (male, 46 yr) who presented initially with reflux symptoms and gastric-type metaplasia, underwent gastric secretory studies that revealed a peak acid output of 16 mmol/L in 1986. During the period 1989 to 1991, his symptoms progressed despite H2 antagonist therapy. In this regard he was reinvestigated, and his peak acid output in 1991 was 0 mmol/L, and subsequent esophageal biopsies demonstrated intestinal metaplasia in four of six biopsies (two biopsies had high-grade dysplasia; the two others had gastric-type metaplasia). He has refused esophageal resection, and is being reviewed regularly at the endoscopy clinic. Flow cytometric analysis of the esophagus in both individuals revealed expression of epidermal growth factor receptor which was increased in the areas of high grade dysplasia, compared with Barrett's mucosa without dysplasia or normal cardiac mucosa. We conclude that alkaline reflux may accelerate the development of Barrett's esophagus (and intestinal type metaplasia) in patients with gastroesophageal reflux disease. The increased expressed of epidermal growth factor receptors in Barrett's mucosa with dysplasia compared with Barrett's mucosa without dysplasia may reflect the higher malignant potential of the former mucosa.

Expression of epidermal growth factor, transforming growth factor alpha and their receptor in gastro-oesophageal diseases

This article is a review of aspects of the expression of the regulatory peptides; epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha), and their receptor (EGF-R) in the epithelium of the human oesophagus and stomach in health and disease. It has become clear that TGF-alpha has increased expression in metaplastic, dysplastic and neoplastic tissue of the oesophagus compared with normal mucosa. The degree of abnormal expression becomes more marked as dysplasia increases. TGF-alpha expression is also increased in gastric neoplasias. EGF has a different pattern of expression, being decreased in oesophagitis and increased in gastritis. Although EGF is present in Barrett's oesophagitis, the expression of EGF does not discriminate between dysplastic and neoplastic epithelium. EGF-R is normally expressed on all gastro-intestinal epithelia, but its expression is increased in Barrett's epithelium, as well as in adenocarcinomas of the oesophagus and the stomach. The two peptides bind to their receptors on the mucosal cell membranes, and the co-expression of peptide and receptor is positively associated with varying degrees of cellular proliferation. The density of receptor expression may modulate the proliferative stimulus, leading to either mitogenic (regulated) or oncogenic (unregulated) growth.

Adverse influence of fibrin sealant on the healing of high-risk sutured colonic anastomoses

The effect of fibrin glue sealing on sutured colonic anastomoses was studied using a 'high-risk' colon anastomosis model in the rat. Animals (n = 104) were randomized to have their sutured anastomosis sealed with fibrin glue or left untreated. They were assessed clinically until they were killed on the fourth day after surgery when contrast radiology, detailed post-mortem examination, anastomotic bursting pressure (ABP) and assessment of adhesion formation were performed. The clinical outcome was worse in the glued group (toxic or death from sepsis: 18 versus seven in the non-glued group; P = 0.0354), which also showed a significantly higher moderate to major leak rate (17 versus two in the non-glued group; P = 0.0009). The median ABP was significantly higher in the glued anastomosis group (96 versus 68 cmH2O in the non-glued group; P = 0.0367). Excessive perianastomotic adhesion formation was significantly greater in the glued group. Microscopic examination showed an extremely intense inflammatory reaction in the glued anastomoses compared with that in the untreated group. These results indicate that sealing of a sutured anastomosis with fibrin glue containing an antiproteinase impairs healing the of anastomotic wound, probably by resisting the ingrowth of vascular granulation tissue during the early stages of repair.

Epidermal growth factor in the oesophagus

Epidermal growth factor (EGF) has been implicated in mitogenesis and oncogenesis in the gastrointestinal tract. To determine the role of EGF in oesophageal disease, its quantity and distribution in the oesophageal mucosa of control subjects and patients with oesophageal disease were studied. Oesophageal biopsy specimens, taken 20-40 cm from the incisors in 72 patients, were graded histologically and adjacent specimens were taken for immunohistochemical analysis of the distribution of EGF. In patients with Barrett's columnar lined oesophagus, specimens were also taken from the gastric cardia for comparison. Twenty two biopsy specimens showed oesophagitis, 20 Barrett's mucosa, and 30 were histologically normal. EGF was found in the capillary endothelium of the normal oesophageal papillae and basal mucosa. Significantly more EGF positive papillae were found in the normal mucosa (81%) than in the inflamed mucosa (42%) (p < 0.001). The 20 patients with Barrett's mucosa showed abnormal expression of EGF in 25% of the isthmus and superficial epithelial cells. This study has shown that EGF is found only in the endothelial cells of the capillaries of the normal oesophageal mucosa and that the peptide is detectable significantly less frequently than normal in the inflamed oesophageal mucosa. EGF is also abnormally present, in large quantities, in the cytoplasm of the epithelial cells of Barrett's mucosa compared with gastric mucosa.

Oncogenes and onco-suppressor gene in adenocarcinoma of the oesophagus

While the activation of the proto-oncogenes has been implicated in the development and progression of cancer of many tissues, the role of oncogenes in the development of oesophageal adenocarcinoma has not been defined. Fifteen patients who had undergone resection for oesophageal adenocarcinoma and 15 who had undergone oesophagectomy or biopsy for Barrett's oesophagus were studied. The latter patients also had adjacent normal gastric mucosa biopsied for comparison with the metaplastic oesophageal mucosa. The mucosal samples were snap frozen and subsequently stained with monoclonal antibodies to the following oncogene associated proteins; c-erbB2 (neu and CE-1) (external domain), c-erbB2 (NCL-CB11) (internal domain), c-src, c-ras, c-myc, c-fos, c-jun, and the onco-suppressor gene--p53. All tumours were well or moderately differentiated adenocarcinomas arising from the lower third of the oesophagus. Eleven specimens showed strong membraneous staining with both c-erbB2 (neu) and c-erbB2 (CBL-CB11). Seven specimens showed strong nuclear staining with p53 onco-suppressor gene. Three specimens were positive for c-ras and c-src, and two were positive for c-jun. In Barrett's epithelium, nine specimens were positive for c-erbB2 (neu and CB11), three were positive for c-src, two were positive for c-ras and c-jun, and one was positive for c-fos. Two of the gastric mucosal biopsy specimens expressed c-erbB2 weakly but no other oncogenes were found. The frequency of positive staining for c-erbB2 is very high, compared with the expression of these genes in other tumours. It is also concluded that errors in the onco-suppressor gene p53, and especially in the external and internal domains of c-erbB2, which is also often expressed in Barrett's mucosa, may be implicated in the development of adenocarcinoma of the oesophagus.

Flow cytometry of oesophageal mucosal biopsies; epidermal growth factor receptor, and CD15

Flow cytometry may be used to examine the properties of single or isolated cells. We have shown that it is possible to disaggregate and label oesophageal epithelial cells for two surface markers, CD15 and epidermal growth factor receptor. We have previously demonstrated these markers in oesophageal squamous cells using immunoperoxidase techniques. These labelled disaggregated cells could then be measured by flow cytometry.

Proliferating cell nuclear antigen in oesophageal diseases; correlation with transforming growth factor alpha expression

This study was designed to correlate mucosal proliferation in Barrett's oesophagus with expression of a growth promoting peptide, transforming growth factor alpha (TGF alpha). Oesophageal mucosa was studied from 50 patients with oesophageal disease who had been treated by oesophagectomy. Histological analysis showed a range of oesophageal pathology - 18 patients had gastric type Barrett's mucosa, 18 had intestinal type Barrett's mucosa, and 14 had oesophageal adenocarcinomas. Sections were stained immunohistochemically for proliferating cell nuclear antigen (PCNA) (an index of cellular proliferation) and TGF alpha. PCNA immunostaining was seen mainly in the basal cells of the neck/foveolar epithelial compartment of the glands in Barrett's oesophagus. However, in mucosa with high grade dysplasia, the proliferative compartment extended upwards into the superficial layers of the glands. At least 2000 cells were counted in each patient to determine the proportion with PCNA immunoreactivity (PCNA labelling index). The labelling index was highest in adenocarcinoma (25%) and in Barrett's intestinal type mucosa with high grade dysplasia (26%) compared with intestinal type mucosa with no significant dysplasia (20%) and Barrett's gastric type mucosa (12%). There was a significant positive correlation between PCNA labelling indices and TGF alpha expression in Barrett's mucosa (p less than 0.01). In glands showing high grade dysplasia, TGF alpha immunoreactivity was seen in the same regions of the glands as PCNA immunoreactivity, indicating the possibility of involvement of TGF alpha in (pre) neoplastic proliferation in Barrett's oesophagus.

Growth regulatory peptides in gastric mucosa

1. Epidermal growth factor and the related peptide transforming growth factor alpha have been implicated in the stimulation of gastric mucosal proliferation. We assessed the immunohistochemical distribution of these peptides and their receptor, epidermal growth factor receptor, in mucosa from the antrum and body of the stomach from 28 patients. Twenty-three of the 56 biopsies were histologically normal (12 antrum and 11 body), whereas the other 33 showed varying degrees of inflammation. 2. Epidermal growth factor, transforming growth factor alpha and epidermal growth factor receptor had maximal density of distribution on the apical surfaces of the superficial epithelial cells, but were also expressed to a lesser extent on neck and body cells of the glandular tissue (P less than 0.05). We also demonstrated that epidermal growth factor expression was greater in the epithelial cells of inflamed mucosa than in those of normal mucosa (P less than 0.05). 3. We assessed mucosal proliferation by the Ki-67 labelling index. Ki-67-positive cells were found predominantly in the neck area of the glands and were more frequent in glandular antral tissue than in body glandular tissue (P less than 0.05). Expression of epidermal growth factor receptor in the neck and isthmus cells had a significant correlation with the Ki-67 labelling index (P less than 0.05). 4. We conclude that epidermal growth factor and epidermal growth factor receptor may be important in the adaptation of gastric mucosa to inflammation.

Membranous expression of carcinoembryonic antigen (CEA) in the normal cervical squamous mucosa

Using a panel of polyclonal and monoclonal antibodies to CEA-related antigens in paraffin-processed cervical biopsies, CEA and NCA expression has been demonstrated on the cell membrane of normal mature cervical squames. Cytofluorimetry of disaggregated cervical squames confirmed membranous expression and immunogold labelling of ultrathin cryostat sections localized CEA to the glycocalyx and to within cytoplasmic membrane-bound vesicles of mature squames. Immunoblotting of cervical tissue showed that most of the CEA reactivity was expressed as a glycoprotein of molecular weight around 180 k, probably CEA itself. Localization of the CEA to the cell membrane of mature cervical squames suggests a key role for these antigens in maintaining the integrity of the squamous mucosa, through the putative function of an adhesion molecule.

Epidermal growth factor receptors in the oesophagus

The quantity and distribution of epidermal growth factor receptors (EGF-R) in oesophageal mucosa was studied in the oesophagus in order to determine its role in oesophageal disease. Fifty five biopsies were taken from different levels of the oesophagus in 25 consecutive patients undergoing endoscopy. Another group of eight patients with histologically proven Barrett's oesophagitis had a biopsy taken from the area of columnar lined oesophagus. A peripheral, membranous pattern was seen predominantly confined to the basal and immediately suprabasal cells in all of the first group of patients. In the superficial cells a few granular cytoplasmic structures were positive. All patients with Barrett's oesophagitis showed EGF-R staining of the surface epithelium. A computerised planimeter was used to determine the proportion of stained areas of squamous cells which were expressed as a percentage of the total area of squamous cells. The difference in the area of cells stained for EGF-R between normal and inflamed oesophageal mucosa (29.5% and 43.1% respectively) was significant (p less than 0.001).