Endocrine Abstracts

Anaplastic Thyroid Carcinoma (ATC) is the most aggressive thyroid gland malignancy characterized by undifferentiated morphology. It has been suggested that cancer stem cells (CSCs) might play a central role in ATC. Previously on the basis of CD133 positivity, our group suggested that CD133+ cancer stem cells (CSCs) might play a central role in ATC. Here we analyzed a panel of different stem cell markers in order to identify a peculiar CSC pattern in ATC.

Aim: i) to characterize CSCs from ex vivo ATC specimens; ii) to evaluate in a well characterized ATC cell line (SW1736) the percentage of CSCs and the influence of transcription factor SOX2 on Oct-4 and Nanog expression and drug resistance.

Methods: Ex vivo: Eight formalin-fixed, paraffin-embedded ATC specimens were analyzed by RT and qRT-PCR, immunohistochemistry and immunofluorescence for pluripotent CSC markers (CD133, SSEA4, Thy1, ABCG2, c-kit, SOX2, Oct-4, Nanog, Lin28, Klf4 and c-Myc). In vitro: CSC marker expression was evaluated in SW1736 cells by qRT-PCR, flow cytometry and immunofluorescence; the SOX2 effect on Oct-4 Nanog and ABCG2 expression and chemosensitivity were evaluated after SOX2 silencing by siRNA method.

Results: Stem cell markers expression in ATCs and SW1736 cell line proved to be as follows in the table.

SOX2 plays a pivotal role in this model: SOX2 silencing down-regulated Oct-4 (67.6%±2.0 P<0.05) and Nanog (85.5%±5.4 P<0.01) expression. SOX2 silencing sensitized SW1736 cells causing a significant mortality increase of 1.8 fold with 10 μM cisplatin and 1.4 (P<0.01) fold with 1.5 μM doxorubicin in comparison to control cells. Conclusions: The analysis of multiple pluripotent stem cell markers is useful to identify CSCs in ATC. In particular, SOX2 exerts a fundamental role in regulating Oct-4 and Nanog expression. Our data suggest that SOX2 switch-off may be essential for overcoming CSC chemotherapy resistance in ATC.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.