Abstract
FOXE1 is a thyroid-specific transcription factor essential for thyroid gland development and maintenance of the differentiated state. Interestingly, a strong association has been recently described between FOXE1 expression and susceptibility to thyroid cancer, but little is known about the mechanisms underlying FOXE1-induced thyroid tumorigenesis. Here, we used a panel of human thyroid cancer-derived cell lines covering the spectrum of thyroid cancer phenotypes to examine FOXE1 expression and to test for correlations between FOXE1 expression, the allele frequency of two SNPs and a length polymorphism in or near the FOXE1 locus associated with cancer susceptibility, and the migration ability of thyroid cancer cell lines. Results showed that FOXE1 expression correlated with differentiation status according to histological sub-type, but not with SNP genotype or cell migration ability. However, loss-and-gain-of-function experiments revealed that FOXE1 modulates cell migration, suggesting a role in epithelial-to-mesenchymal transition (EMT). Our previous genome-wide expression analysis identified Zeb1, a major EMT inducer, as a putative Foxe1 target gene. Indeed, gene silencing of FOXE1 decreased ZEB1 expression, whereas its overexpression increased ZEB1 transcriptional activity. FOXE1 was found to directly interact with the ZEB1 promoter. Lastly, ZEB1 silencing decreased the ability of thyroid tumoral cells to migrate and invade, pointing to its importance in thyroid tumor mestastases. In conclusion, we have identified ZEB1 as a bona fide target of FOXE1 in thyroid cancer cells, which provides new insights into the role of FOXE1 in regulating cell migration and invasion in thyroid cancer.
Highlights
Thyroid cancer is the most commonly occurring endocrine malignancy and its incidence has steadily increased over the last four decades, accounting for 1% of all annual cancer diagnoses (Davies & Welch 2006, Lim et al 2017)
Given that FOXE1 has been described as a susceptibility gene in thyroid cancer, we first compared its level of expression in a panel of human thyroid cancer cell lines with its expression in the normal thyroid follicular cell line NThy-ori-3-1 (NThyOri)
The cell lines used covered the spectrum of thyroid neoplasms, from well-differentiated Papillary thyroid carcinoma (PTC) and follicular thyroid carcinomas (FTC) to anaplastic thyroid carcinoma (ATC), which is the most aggressive malignancy
Summary
Thyroid cancer is the most commonly occurring endocrine malignancy and its incidence has steadily increased over the last four decades, accounting for 1% of all annual cancer diagnoses (Davies & Welch 2006, Lim et al 2017). Papillary thyroid carcinoma (PTC), a carcinoma of follicular cell origin, is the most frequent form of differentiated thyroid carcinoma and represents 80–85% of all thyroid malignancies (Zaballos & Santisteban 2017). Initiation and progression of thyroid cancer results from the acquisition of multiple genetic alterations.
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