Fibronectin-1 expression is increased in aggressive thyroid cancer and favors the migration and invasion of cancer cells

• EMT markers are overexpressed in papillary thyroid cancers.
• Fibronectin-1 is the marker most highly overexpressed in aggressive tumors.
• FN1 silencing impairs thyroid cancer cell growth, migration, and invasion.

In this study we analyzed the expression levels of markers of epithelial-to-mesenchymal transition (EMT) in several papillary thyroid carcinomas (PTCs) and the relation with tumor genotypes and clinicopathological characteristics. The role of fibronectin-1 (FN1) was investigated by analyzing the effects of FN1 silencing in two human thyroid cancer cell lines.Most of EMT markers were significantly over-expressed in a group of 36 PTCs. In particular, FN1 mRNA levels were higher in tumor vs non-tumor tissue (117.3, p < 0.001) and also in aggressive and BRAFV600E samples. Similar results were observed (and confirmed at the protein level) when FN1 expression was analyzed in a validation group of 50 PTCs and six lymph node (LN) metastases. Silencing of FN1 in TPC-1 and BCPAP thyroid cancer cells significantly reduced proliferation, adhesion, migration, and invasion in both cell lines.Collectively, our data indicate that FN1 overexpression is an important determinant of thyroid cancer aggressiveness.