Introduction. The potential use of non-steroidal anti-inflammatory drugs (NSAIDs) in the prevention of esophageal cancer has been highlighted recently. Taking aspirin was reported to reduce the risk of developing Barrett's esophagus and prevent the development of both esophageal squamous cell cancer and adenocarcinoma. However, the underlying mechanism is still unclear. Some researchers indicated that aspirin could induce tumor cells apoptosis and might modulate cancer stem cells regulation through the Wnt/beta-catenin pathway. Pervious results have shown that side population (SP) cells in esophageal cancer cell lines have stem cell-like properties and may be responsible for therapy resistance. Our objective was to determine whether aspirin by targeting Wnt signaling affects the biological properties of side population cells in esophageal cancer and its therapeutic effect both in vitro and in vivo.

Methods. In vitro cytotoxicity assays using aspirin were performed in three different esopahgeal cancer cell lines (OE19, OE21, and OE33). After treatment with aspirin Hoechst 33342 staining was used to define the proportion of SP cells. And the expression of Wnt signaling targets with and without aspirin treatment was further evaluated by PCR array. SP and non-SP cells in OE19 were isolated by flow cytometric sorting and further treated with aspirin. The efficacy of aspirin alone and combined with 5-FU and Cisplatin administration by intraperitoneal injection regarding OE19 tumorigenicity was evaluated in a subcutaneous xenograft model.

Results. Aspirin inhibits in a dose and time dependent manner cell proliferation in esophageal cancer cell lines. In OE19, SP cells were dramatically decreased from 19.7±1.0 to 6.9±1.0, 3.4±0.9 and 1.8±0.4 (p 2 fold change). In particular, aspirin can reduce 5-FU or cisplatin induced enhancement of SP and displayed a relative stronger effect on SP proliferation as compared to non-SP cells together with a significant reduction of ABCG2+ subpopulation. 5-FU and Cisplatin combined with daily aspirin severely impaired tumor weight comparing to chemotherapy alone (0.14±0.11g vs 0.75±0.2g, p=0.0004) However, administration of aspirin alone did not have effect on tumor growth significantly as compared to vehicle group (1.58±0.36g vs 1.50±0.28, p=0.728).

Conclusion. Aspirin may affect on esophageal cancer cells by targeting the chemoresistant side population cells through wnt signaling pathway. This finding indicates a potential therapeutic strategy considering NSAIDs for esophageal cancer.

Citation Format: Yue Zhao, Bettina Schwarz, Lu Zhao, Yan Wang, Anneli Tischmacher, Josef Mysliwietz, Joachim Ellwart, Qi Bao, Hanno Nieß, Dominik Modest, Peter Camaj, Karl-Walter Jauch, Peter Nelson, Christiane Bruns. Aspirin decreases side population cells by targeting the Wnt pathway in esophageal cancer cells in vitro and enhances the combination chemotherapeutic effect of 5-FU and cisplatin in vivo. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3717. doi:10.1158/1538-7445.AM2013-3717