Non-proliferative capacity of endocrine cells of the human gastro-intestinal tract

Correctly identifying the cells of origin is essential for tailoring treatment and understanding the emergence of cancer stem cells and late metastases

Malignancy manifests itself by deregulated growth and the ability to invade surrounding tissues or metastasize to other organs. These properties are due to genetic and/or epigenetic changes, most often mutations. Many aspects of carcinogenesis are known, but the cell of origin has been insufficiently focused on, which is unfortunate since the regulation of its growth is essential to understand the carcinogenic process and guide treatment. Similarly, the concept of cancer stem cells as cells having the ability to stop proliferation and rest in a state of dormancy and being resistant to cytotoxic drugs before "waking up" and become a highly malignant tumor recurrence, is not fully understood. Some tumors may recur after decades, a phenomenon probably also connected to cancer stem cells. The present review shows that many of these questions are related to the cell of origin as differentiated cells being long-term stimulated to proliferation.

Gastrin and Gastric Cancer

Gastric cancer although occurring in reduced frequency is still an important disease, partly because of the bad prognosis when occurring in western countries. This decline in occurrence may mainly be due to the reduced prevalence of Helicobacter pylori (Hp) infection, which is the most important cause of gastric cancer. There exist many different pathological classifications of gastric carcinomas, but the most useful seems to be the one by Lauren into intestinal and diffuse types since these types seldom transform into the other and also have different epidemiology. During the nearly 30 years that have passed since the groundbreaking description of Hp as the cause of gastritis and gastric cancer, a continuous search for the mechanism by which Hp infection causes gastric cancer has been done. Interestingly, it is mainly atrophic gastritis of the oxyntic mucosa that predisposes to gastric cancer possibly by inducing hypoacidity and hypergastrinemia. There are many arguments in favor of an important role of gastrin and its target cell, the enterochromaffin-like cell, in gastric carcinogenesis. The role of gastrin in gastric carcinogenesis implies caution in the long-term treatment with inhibitors of gastric acid secretion inducing secondary hypergastrinemia, in a common disease like gastroesophageal reflux disease.

The normal neuroendocrine cells of the upper gastrointestinal tract lack E-cadherin

OBJECTIVE

E-cadherin plays a crucial role in the adhesion between epithelial cells and thus epithelial integrity. Moreover, germline mutations in the E-cadherin gene (CDH1) causing loss of E-cadherin function (adhesion) leads to hereditary gastric cancer of the diffuse type, according to Laurén. Even sporadic gastric carcinomas of the diffuse type often lose E-cadherin expression due to mutations. Lack of E-cadherin has been recorded at an early phase in such carcinomas. For 25 years, we have provided evidence for neuroendocrine (NE) cell origin of gastric carcinomas of diffuse type. The present study was, therefore, done to examine whether normal NE cells in the gastrointestinal tract express E-cadherin or not.

METHODS

During upper gastrointestinal endoscopy, biopsies were taken from normal oxyntic mucosa, gastric carcinoids, gastric carcinomas, and from normal duodenal mucosa. Tissues were examined by immunohistochemistry (IHC) using antibodies toward chromogranin A, synaptophysin, and E-cadherin. Isolated mucosal cells were prepared from biopsies of normal mucosa and examined by antibodies against the same markers by immunofluorescence.

RESULTS

Normal gastrointestinal NE cells did not express E-cadherin as assessed by IHC or immunocytochemistry. No expression of E-cadherin was found on tumor cells from gastric carcinoids or cancer of diffuse type examined by IHC.

CONCLUSION

Our findings, which are in contrast to some previous studies, may explain why there is a discrepancy between lack of atypia and malignant biological behavior of such tumors. Since they normally lack the adhesion molecule E-cadherin, reflected in their spread occurrence, only minor changes may result in malignant behavior.

The regulation of gastric acid secretion - clinical perspectives

The purpose of this review, based upon 40 years of research, is to clear old controversies. The gastric juice is a strong acid with active enzymes (pepsin and lipase); ideal for killing swallowed microorganisms. Totally isolated rat stomach and histamine determination. Human gastric carcinomas were examined for ECL cell differentiation because tumours found in rodents after dosing with inhibitors of acid secretion were reclassified to be of ECL cell origin. The gastrin receptor is localized to the ECL cell only, where gastrin stimulates the function and growth. Drug-induced hypo-acidity induces hypergastrinaemia and ECL cell hyperplasia responsible for rebound acid hypersecretion. Every condition with long-term hypergastrinaemia disposes to ECL cell neoplasia. In man, both atrophic gastritis and gastrinoma lead to ECL cell carcinoids. Proton pump inhibitors induce hypergastrinaemia with ECL cell hyperplasia and ECL cell carcinoids that disappear when stopping treatment. The gastrin antagonist netazepide induces regression of ECL cell carcinoids due to atrophic gastritis. Human gastric carcinomas of diffuse type, particularly the signet-ring subtype, show ECL cell differentiation, suggesting involvement of gastrin in the carcinogenesis. Helicobacter pylori (Hp) causes gastritis and peptic ulcer, and when infecting the antrum only gives a slight hypergastrinaemia with acid hypersecretion predisposing to duodenal ulcer, but protecting from gastric cancer. When Hp infection spreads to oxyntic mucosa, it induces atrophy, reduced acid secretion and marked hypergastrinaemia and cancer.It is remarkable that the interaction between Hp and gastrin may explain the pathogenesis of most diseases in the upper gastrointestinal tract.

Chromogranin A-positive tumor cells in human esophageal squamous cell carcinomas

Gastrointestinal cancers have frequently shown neuroendocrine (NE) differentiation, but whether NE differentiation occurs in esophageal squamous cell carcinoma (ESCC) remains unclear. In this study, tissue sections obtained from 43 patients with ESCC from a high-incidence area of Northern China were used for the assessing of NE differentiation by immunohistochemistry using antibody against chromogranin A (CGA). In addition, the malignant characteristics and proliferation capacity of CGA-positive cells were also examined by immunohistochemistry. The clinicopathological significance of these CGA-positive tumor cells in ESCC was assessed. Of 43 ESCC samples, CGAimmunoreactive tumor cells were detected in 10 cases (23.26%). However, the CGA-positive tumor cells were scattered at a very low number among non-immunoreactive tumor cells and were rarely constituted a major part of cancer cell nests. Only 4.65% (2/43) cases showed a high density (>10 cells but <1% of total tumor cell mass) of CGA-positive tumor cells. P53 immunoreactivity was frequently shown, while Ki67 was hard to detect in these CGApositive cells. In addition, no relationship between CGA positivity rate and clinicopathological parameters was found. Thus, we concluded that lowdensity CGA-positive tumor cells can be detected in ESCC, supporting the notion that heterogeneous NE differentiation also exists in tumors that lack neuroendocrine cells in their normal epithelial counterparts.