50P - Integrin-fibronectin interplay is a pivotal biological and clinical determinant in papillary thyroid carcinoma

Background

Papillary thyroid carcinoma (PTC) has a specific integrin expression signature that correlates with histopathology, specific driver gene mutations, and aggressiveness of the disease. α3β1 integrin is overexpressed, it is involved in PTC cell motility and invasion and is associated with an advanced disease and a worst outcome. Histopathology studies indicate that fibronectin 1 (FN1) and its integrin ligand αVβ3 are overexpressed in PTC. In normal thyroid cells, fibronectin (FN) stimulates DNA synthesis, proliferation and survival through αVβ3 binding.

Methods

The mRNA expression of integrins and FN1 genes in normal thyroid tissues and PTC were assessed in the TCGA database. -The level of FN and αVβ3 in was assessed by immunofluorescence in PTC cell lines (BCPAP, K1) and in a normal thyroid cell line (Nthy-ori3-1). -The release and deposition of FN were estimated by enzyme-linked immunoassay. - The proliferation was measured by MTT assay. -The silencing of gene FN1 in the K1 cell line was performed with KN2.0, non-homology mediated CRISPR knockout kit (ORIGENE®).

Results

Analysis of the TCGA database on 402 PTC and 82 healthy tissues demonstrates that FN1 mRNA is 60 times more expressed in PTC than in healthy tissue and that the ITGAV and ITGB1 subunits are more expressed. The increase in FN1 and ITGAV mRNA expression is associated with metastatic lymph nodes, more advanced staging, extrathyroidal extension, and higher risk. PTC cells show higher expression of integrin αVβ3, the main receptor of FN1 and at the same time a high production of fibronectin. The gene FN1 was silenced in K1 cell line (K1FN1-/-). Both K1 and K1FN1-/- seeded in collagen coated plates attached and survived in the absence of serum. While K1 proliferated under these culture conditions, proliferation was almost absent in K1FN1-/- and was rescued by soluble FN.

Conclusions

Papillary thyroid carcinoma cells express high amounts of αVβ3 integrin and produce more fibronectin. - Fibronectin/ αVβ3 interaction could be a mechanism of disease progression in PTC. - Fibronectin can be a powerful prognostic indicator and a site of pharmacological intervention.

Editorial acknowledgement

Clinical trial identification

Legal entity responsible for the study

University of Salerno.

Funding

Department of Medicine, Surgery and Dentistry, University of Salerno.

Disclosure

All authors have declared no conflicts of interest.