Abstract 1411: An analysis on the usefulness of ALDH in esophageal squamous cell carcinoma

Abstract

Abstract (Background) Esophageal squamous cell carcinoma (ESCC) is a highly malignant cancer with a poor prognosis. In recent years, the existence of tumor-initiating cells (TICs) and their treatment-resistance have been noted in gastrointestinal cancer. It is thought that TICs are major contributors to cancer relapse, and removing the TICs might improve the radical cure rate. However, there have been only a few reports on the TICs of ESCC. Theoretically, the TICs can be treated by either actively removing them or making them differentiate into cells that are sensitive to chemotherapy. However, no such strategies have been established yet. (Methods) As a pre-planning stage for novel treatment strategies focused on TICs of ESCC, we identified the TIC fraction and then elucidated their characteristics, using ESCC cell lines (T.Tn and TE series). (Results) During the sphere formation assay, spheres were formed in cultures of the ESCC cell lines T.Tn, TE1 and TE2. We dissociated the spheres and cultured the resulting cells under non-adherent conditions. The spheres were formed again, so the capacity of the cells for self-renewal was confirmed. Furthermore we examined the sensitivity of the cells making up the spheres to an anticancer agent using the MTT assay. The cells showed resistance to CDDP. It is believed that the cells making up the spheres included cells with TICs properties, so we analyzed these cells for their expression of CD24, 44, 133 and EpCAM, which were reported to be TIC markers in other cancers, by flow cytometry. Compared to the ratio in the total cells, the proportion of positive cells in the cells making up the spheres was similar or lower. Therefore, we examined the expression of CD90, which has been reported to be a marker of liver cancer, in the same way. The percentage of positive cells in the cells making up the spheres was slightly increased compared to the overall cell population, but few CD90-positive cells were detected in the spheres by immunohistochemistry. It was thought that separation by cell surface markers, such as CD24, 44, 90, 133 and EpCAM was difficult, so we focused on the ALDH, which was one of functional markers. It was revealed that about 30% of total cells were positive, but almost all of the sphere cells were positive by ALDEFLUOR and immunohistochemistry. (Discussion) The ESCC cell lines T.Tn, TE1 and TE2 form spheres, so these were considered to be useful in the present experimental system. However, separation by cell surface markers was difficult, so we are currently considering separation by functional markers, including ALDH enzyme activity. We will analyze the TIC markers continuously and identify the TIC fraction of ESCC. Note: This abstract was not presented at the meeting. Citation Format: Kentaro Murakami. An analysis on the usefulness of ALDH in esophageal squamous cell carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1411. doi:10.1158/1538-7445.AM2015-1411