Abstract 4898: Association of CD44 expression and ALDH1 activity in thyroid cancer.

Abstract

Abstract Background: Anaplastic thyroid cancer (ATC) is considered to be one of the most aggressive human malignancies, and the mean survival time (MST) after diagnosis is approximately six months, regardless of treatments. ATC is known to arise from differentiated thyroid cancers such as papillary (PTC) or follicular (FTC) cancers. The purpose of this study is to examine whether the characteristics of cancer stem cell are associated with ATC. Materials and methods: One PTC cell line (TPC1), one FTC cell line (FTC-133), and two ATC cell lines (FRO, ACT-1) were analyzed for surface markers (CD24/CD44, CD44 variant isoform, EpCAM), and ALDH1 enzymatic activities (ALDEFLUOR) by FACS. In addition, relative mRNA expression of these molecules were determined by real-time RT-PCR. Results: CD44s (standard form) expressions in the PTC cell line (TPC1) and the FTC cell line (FTC-133) were higher than those in the ATC cell lines (FRO and ACT-1). On the other hand, ALDH1 activities of ATC cell lines were higher than those of the PTC and the FTC cell lines. An inverse correlation between the expression of CD44s and ALDH1 activity was observed in the thyroid cancer cell lines. As for the expressions of CD44 variant forms, ACT-1 showed a higher and FRO showed a moderate expressions of CD44v6. On the other hand, either TPC1 or FTC-133 showed negative expression of CD44v6. The expressions of EpCAM in the ATC cell lines were higher than those in the differentiated cancer cell lines, and EpCAM expressions were inversely correlated with the expressions of CD44s. ATC cell lines showed higher levels of ALDH1 enzymatic activities and EpCAM expressions compared with those in the differentiated cancer cell lines. A strong positive correlation was observed between the expression of EpCAM and ALDH1 activity in the thyroid cancer cell lines. Both ALDH1 and EpCAM mRNA expressions were higher in the ATC cell lines compared with those in the differentiated cancer cell lines in the RT-PCR analyses. Conclusion: In our present study, the expressions of CD44 and EpCAM, and ALDH1 enzymatic activity were different between the differentiated thyroid cancer cell lines and the anaplastic thyroid cancer cell lines. Our data suggest that these molecules might be involved in the development and aggressive phenotype of anaplastic thyroid cancer. Citation Format: Toshihiro Okada. Association of CD44 expression and ALDH1 activity in thyroid cancer. [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 4898. doi:10.1158/1538-7445.AM2013-4898