Thyroid Follicular Cell Loss of Differentiation Induced by MicroRNA miR-17-92 Cluster Is Attenuated by CRISPR/Cas9n Gene Silencing in Anaplastic Thyroid Cancer.

Loss of the expression of thyroid differentiation markers such as sodium iodide symporter (NIS) and, consequently, radioiodine refractoriness is observed in aggressive papillary thyroid cancer and anaplastic thyroid cancer (ATC) that may harbor the BRAF mutation. Activation of the BRAF oncogene in thyroid follicular cells induces the expression of the cluster that comprises seven mature microRNAs (miRNAs). miRNAs are a class of endogenous small RNAs (∼22 nt) that regulate gene expression post-transcriptionally. Indeed, is overexpressed in ATC, and prediction shows the potential targeting of thyroid transcription factors and tumor suppressor pathways. In this study, we aimed to investigate the role of the cluster in thyroid cell differentiation and function. silencing was performed using CRISPR/Cas9n-guided genomic editing of the gene in the KTC2 ATC cell line, and cluster or individual miRNAs were overexpressed in PCCl3 thyroid cells to evaluate the influence in thyroid cell differentiation and cell function. In this study, we demonstrate that CRISPR/Cas9n gene editing of the cluster results in promotion of thyroid follicular cell differentiation (NIS, thyroperoxidase, thyroglobulin, PAX8, and NKX2-1 expression) in the KTC2 ATC cell line and inhibits cell migration and proliferation by restoring transforming growth factor beta (TGF-β) signaling pathway responsiveness. Moreover, induction of the cluster in normal thyroid follicular cells strongly impairs thyroid differentiation and induces a pro-oncogenic effect by blocking TGF-β signaling and increasing cell migration. is a potent regulator of thyroid follicular cell differentiation, and CRISPR/Cas9n-mediated editing of the gene efficiently blocks expression in the KTC2 ATC cell line, resulting in improvement of thyroid differentiation. Thus, targeting could provide a potential molecular approach to restoring thyroid cell differentiation and NIS expression in aggressive thyroid cancer.