Background: Prostaglandin E2 is one of the potential products that promotes development of tumors and also is a strong inducer of M2 phenotype macrophages, which contribute to tumor development in the immunosuppressed microenvironment. Hangeshashinto (TJ-14), a Japanese traditional medicine (Kampo medicine), has been reported to be effective in preventing chemotherapy-induced oral mucositis through the reduction of prostaglandin E2. We previously developed a surgical rat reflux model of esophageal cancer and used this well-established animal model to investigate the action of TJ-14 in preventing esophageal cancer. We also assessed the effect of TJ-14 on the downregulation of prostaglandin E2 production, utilizing esophageal squamous cell carcinoma cell line exposed to bile acid. Methods: An end-to-side esophagojejunostomy was performed for the reflux model. A daily oral diet was subsequently administered, consisting of either diet-incorporated TJ-14 or standard diet as a control group. The rats were killed at 40 weeks after surgery. The incidence of esophageal cancer, Barrett's metaplasia, and proliferative hyperplasia were assessed histologically. CD163, a M2 phenotype macrophage marker, was assessed with immunohistochemistry. Prostaglandin E2 enzyme immunoassay and lactate dehydrogenase assay were performed on chenodeoxycholic acid or gastroesophageal reflux contents exposed to esophageal squamous cell carcinoma cell line. Results: Sixty-seven percent of the controls (n = 12) developed esophageal cancer, but animals that received TJ-14 (n = 10) had a cancer incidence of 10% (P =.007). Barrett's metaplasia was found in 83% of the rats in the control group and 50% of the rats in the TJ-14 indicating a protective tendency of TJ-14 (P =.095). All of the rats developed proliferative hyperplasia. The number of M2 phenotype macrophage were significantly decreased in the TJ-14 group compared to the control group in both Barrett's metaplasia and esophageal cancer lesions. TJ-14 inhibited chenodeoxycholic acid or gastroesophageal reflux content–induced prostaglandin E2 production in esophageal squamous cell carcinoma cell. Conclusion: TJ-14 reduced the incidence of reflux-induced esophageal cancer and the infiltration of M2 macrophages in a surgical rat model or suppressed prostaglandin E2 production in esophageal squamous cell carcinoma cell. Further investigation is required regarding the potential clinical use of TJ-14 as an esophageal cancer chemopreventive agent.
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