HMGA2 Overexpression in Papillary Thyroid Cancer Promotes Thyroid Cell Dedifferentiation and Invasion, and These Effects Are Counteracted by Suramin.

Thyroid cancer is the most prevalent endocrine malignancy, and papillary thyroid carcinoma (PTC) is the most common type of thyroid malignancy. While PTC generally has a favorable prognosis, a subset dedifferentiates into aggressive forms. However, the molecular mechanisms responsible for aggressiveness and dedifferentiation are still poorly understood. We previously showed that HMGA2, a non-histone architectural transcription factor overexpressed in PTC, is involved in cell invasion. This study aimed to further analyze the role of HMGA2 in PTC tumorigenesis by exploring the expression of thyroid-specific and EMT-related genes following HMGA2 knockdown in thyroid cancer cell lines. Then, the clinical relevance of our data was evaluated in vivo. HMGA2 silencing did not modulate the expression of EMT related genes but led to the increased expression of thyroid differentiation genes. Our data also suggest that the MAPK pathway induces thyroid cell dedifferentiation through HMGA2. On the other hand, forskolin, promoting thyroid differentiation, decreased HMGA2 expression. The negative correlations between HMGA2 and thyroid-specific gene expressions were confirmed in a transgenic mouse model of PTC and in human PTC. Finally, we showed that HMGA2 inhibition by suramin reduced cell invasion and induced differentiation expression in vitro, indicating a new therapeutic strategy for treating thyroid cancer.