Abstract 5360: Towards identification of cancer stem cells in esophageal adenocarcinoma

Abstract

Abstract Introduction: Cancer stem cells (CSC) are characterized by stem cell properties such as self-renewal potential and multilineage differentiation capacity. CSC's are thought to be the main drivers of tumor formation and progression and the main cause of therapy resistance and metastatic spread. In contrast to other cancer types such as glioblastoma and colon cancer, attempts thus far have not resulted in the identification of a proven CSC population in esophageal cancer. Therefore in this study we aim to identify and characterize CSC's in esophageal adenocarcinoma (EAC). Methods and Results: To address this goal, we attempted to culture CSC's from primary untreated EAC biopsy material using serum-free medium formulations that, however, have not been successful thus far. As an alternative model we employed two EAC cell lines, OE19 and OE33, which we were able to maintain as spheroids in serum-free Neural Basal Medium thought to enrich for stem cell growth. Dissociation of spheres and limiting dilution assays showed enhanced spheroid forming potential in OE19 but not in OE33 when compared to cells obtained from normal 10% FCS monolayer cultured counterparts. Next, the expression of several known CSC markers was determined by FACS analysis to determine self-renewal potential of sorted fractions in subsequent limited dilution assays. Side population, ALDH1, CD44/CD24 fractions were tested of which only CD44+ /CD24+ cells showed enhanced capacity to form spheroids. Tumor growths of these populations are currently being evaluated on immune-compromised mice. Other stem cell markers such as OCT4 and SOX2 were enhanced in OE19 spheroids compared to 10% FCS cultured cells. However, in OE33 spheroids expression of these markers were unchanged or downregulated. Since EAC derives from dysplastic epithelia with intestinal characteristics in Barrett's esophagus, we examined the status of the Wnt pathway known to be involved in maintenance of intestinal/ colon (cancer) stem cells. In the EAC cells β-catenin expression was present that could be enhanced by LiCl. Reporter assays to determine Wnt- activity are in progress. Finally, the sensitivity of spheroid versus monolayer cultured OE33 cells to 5-FU, cisplatin and paclitaxel was evaluated. Sensitivity did not differ much, although monolayer cultured OE33 cells were more resistant for 5-FU. Conclusion: Given the differences in the two spheroid models regarding spheroid forming potential, CSC-marker expression and chemosensitivity, caution is warranted when using esophageal adenocarcinoma cell line derived spheroids as model for CSC's. However, CD44 and CD24 might have a potential as CSC-markers in EAC, which is currently further corroborated. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5360. doi:1538-7445.AM2012-5360