Gastric Intestinal Metaplasia and Tamoxifen: Can We Reverse the Inevitable?

Abstract

Gastric intestinal metaplasia can occur after chronic infection with Helicobacter pylori and is considered a precursor of gastric adenocarcinoma. Thus, interventions which can reverse intestinal metaplasia may reduce the incidence of gastric cancer. The manuscript by Moon et al. published in this issue of Digestive Diseases and Sciences [1] reports somewhat surprising results suggesting that Korean women receiving chronic tamoxifen treatment after breast cancer surgery showed a decrease in intestinal metaplasia. Previous work from the Mills laboratory had shown that high doses of tamoxifen treatment in mice led to loss of parietal cells and the evolution of Spasmolytic Polypeptide Expressing Metaplasia (SPEM). Nevertheless, in patients receiving lower therapeutic doses of tamoxifen for an extended period, the findings of Moon et al. indicate that tamoxifen may in fact impair progression of metaplasia to intestinal metaplasia. Importantly, since patients taking aromatase inhibitors did not alter the extent of intestinal metaplasia, the tamoxifen effects observed are likely due to an off-target effect rather than one associated with estrogen receptor blockade. Previous investigations have noted off-target effects of tamoxifen at various levels including alterations in calcium signaling [2], ceramide metabolism [3] and the parietal cell protonophore activities previously proposed by the Mills laboratory [4]. Thus, while it is difficult to define the mechanisms that may be responsible for the observed mucosal alterations in this treatment cohort, the results are nevertheless encouraging for the development of interventions which alter the natural history of metaplasia in the stomach.The authors acknowledge the limitations of this retrospective study. A critical question left by these studies focuses on the impact of tamoxifen treatment on the mucosal lineages. While the report demonstrates that women receiving tamoxifen have a reduced amount of intestinal metaplasia, it is not at all clear that the loss of intestinal metaplasia leads to re-establishment of a normal mucosa. Recent investigations have supported the concept that loss of parietal cells initiated by H. pylori infection leads initially to the development of Spasmolytic Polypeptide Expressing Metaplasia (SPEM) and then over time SPEM evolves into intestinal metaplasia [5]. Unfortunately, the present study did not examine either the state of remaining atrophy or the presence of SPEM in tamoxifentreated patients. Interestingly, the progression of metaplasia from SPEM to intestinal metaplasia and neoplasia may be driven by inflammatory cells, especially macrophages [6]. Indeed, alterations in inflammatory cell response are the most likely explanation for the off-target influences of tamoxifen. While the data in the present study suggest that the inflammation scores were not significantly improved by tamoxifen treatment, there is no way to judge whether this qualitative determination would reflect changes in macrophage subsets. Further studies will need to add...

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