J Cancer 2017; 8(9):1629-1639. doi:10.7150/jca.18855 This issue

Research Paper

Thyrospheres from B-CPAP Cell Line with BRAF and TERT Promoter Mutations have Different Functional and Molecular Features than Parental Cells

Paola Caria1, Rita Pillai1, Tinuccia Dettori1, Daniela Virginia Frau1, Patrizia Zavattari1, Gabriele Riva2, Gabriele Romano2, Fabiana Pani3, Angela Bentivegna2, Roberto Giovannoni2, Fabio Pagni2, Valeria Sogos1, Roberta Vanni1✉

1. Department of Biomedical Sciences, University of Cagliari, Italy;
2. School of Medicine and Surgery, University of Milano-Bicocca, Italy;
3. Department of Medical Sciences, University of Cagliari, Italy.

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Caria P, Pillai R, Dettori T, Frau DV, Zavattari P, Riva G, Romano G, Pani F, Bentivegna A, Giovannoni R, Pagni F, Sogos V, Vanni R. Thyrospheres from B-CPAP Cell Line with BRAF and TERT Promoter Mutations have Different Functional and Molecular Features than Parental Cells. J Cancer 2017; 8(9):1629-1639. doi:10.7150/jca.18855. Available from https://www.jcancer.org/v08p1629.htm

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Human thyroid cancer derived cell lines are widely used to study the mechanisms involved in thyroid carcinogenesis. However, there is limited availability of non-cross-contaminated cancer cell lines derived from papillary thyroid carcinoma (PTC), and the B-CPAP cell line is one of the few such lines. B-CPAP cells have been genetically and cytogenetically well-characterized, but details of their stemness features remain uncertain. Considering that this cell line is extensively used for in vitro studies on thyroid tumorigenesis, we broaden its functional and molecular profiles as well as the tumorigenic capacity. We used functional assays (sphere-forming capacity and efficiency), assessed self-renewal and propagation efficiency and tested in vivo tumorigenicity in Hsd:Athymic Nude-Foxn1nu mice. Expression of markers of stemness, differentiation, and epithelial-mesenchymal transition were estimated at RNA and protein levels in adherent parental cells and sphere-forming cells. Functional aspects and stemness features were compared with normal thyrocytes. Protein expression of xenograft tumors was evaluated by immunohistochemistry. B-CPAP sphere-forming cells were able to form thyrospheres theoretically indefinitely in an appropriate serum-free medium, reverting to the adherent parental cell phenotype when cultured in differentiation medium. Different expression of ALDH1-A1 and CD44 stemness markers and TTF-1 and CK19 differentiation markers allowed discrimination between isolated sphere-forming cells and adherent parental cells, indicating that sphere-forming cells retained stem-like features. In keeping with these observations, tumorigenicity assays confirmed that, relative to parental adherent cells, thyrospheres had enhanced capacity to initiate xenograft tumors. Thyrospheres from normal cell line retained very low functional capacity, as well as different stemness markers expression compared to tumor thyrospheres. Our findings may constitute a useful background to develop an in vitro model for assessing the origin and progression of papillary thyroid carcinoma bearing BRAFV600E and TERT promoter mutations.

Keywords: thyrosphere, B-CPAP cell line, TERT mutation, papillary thyroid carcinoma.