Chronic tamoxifen use is associated with a decreased risk of intestinal metaplasia in human gastric epithelium

Guilt by association: intestinal metaplasia does not progress to gastric cancer

PURPOSE OF REVIEW

This review integrates the new thinking about relationships between gastric cancer and intestinal metaplasia/pseudopyloric metaplasia (SPEM). We address whether recent studies have closed or widened the knowledge gap regarding gastric cancer pathogenesis in mice or humans.

RECENT FINDINGS

Recent studies in mouse models have provided a variety of new insights into the cellular origin and progression of events resulting in gastric cancer. Many suggest a direct transformation from intestinal metaplasia/pseudopyloric metaplasia/SPEM to gastric cancer. However, results from different investigator and models are conflicting and often describe events not present in studies in humans.

SUMMARY

Both Helicobacter pylori-associated and autoimmune gastritis may produce gastric atrophy with extensive intestinal metaplasia and an abnormal gastric microbiome. However, only H. pylori gastritis carries a risk for adenocarcinoma. The differences reported with mouse models can best be explained as the results of different models of regeneration and repair rather than as models of gastric cancer. Overall, the data remains consistent with the original hypothesis that gastric cancer results from increased genetic instability of gastric stem cells rather than a direct transition from metaplasia to cancer. Intestinal metaplasia, pseudopyloric metaplasia, and SPEM have all been falsely accused based on guilt by association.

Risk factors for gastric intestinal metaplasia

Gastric intestinal metaplasia is the most common precancerous lesion of gastric cancer. Due to the unsatisfying treatment efficacy for gastric cancer especially advanced gastric cancer, the key steps of prevention and treatment of gastric cancer are lowering the incidence and improving the early diagnosis. Therefore, it is very important to clarify the risk factors associated with gastric cancer and its precancerous lesion for first-line prevention of gastric cancer. Accumulated evidence indicates that the development of gastric intestinal metaplasia is closely related to Helicobacter pylori infection, age, sex, family history of gastric cancer, smoking, high salt diet, bile acid reflux and so on. This review mainly focuses these factors associated with gastric intestinal metaplasia.

Changing the natural history of metachronous gastric cancer after H. pylori eradication

Metachronous gastric cancer occurs frequently following endoscopic removal of an early gastric cancer. H. pylori eradication significantly reduces that risk. While, the pathogenesis of this phenomenon remains unclear, it is clear that the natural history of metachronous gastric cancer is altered following H. pylori eradication. Genetic instability of host cells induced by inflammation, H. pylori, host or environmental factors can result in the production of malignant cells. H. pylori eradication reduces and alters the inflammation, and can reverse epigenetic damage and abnormal expression of miRNA's. Fundamentally, H. pylori eradication stops the progression and may reverse some of the damage to the mucosa resulting in improved acid secretion and improving the gastric microbiome. Because the risk of developing metachronous cancer varies among patients, prospective research is needed to identify reliable biomarkers to predict development of metachronous cancer as well as to define surveillance methods, intervals, and duration. Some candidate examples of prognostic or predictive biomarkers for the prediction of subsequent risk include the presence or absence, titers, and changes in anti-H. pylori IgG and or anti-CagA antibodies, serum pepsinogens, gastrin, and miRNAs.