Endocrine Abstracts

The most frequent mutation in papillary thyroid carcinoma (PTC) is the p.V600E of the BRAF gene. This mutation leads to the aberrant activation of the RAS / BRAF / MEK / ERK pathway and consequently to the under-regulation of thyroid-specific genes, resulting in uncontrolled growth and de-differentiation of cancer cells. In this work, we analyzed the transcriptomics data produced by the TCGA project using a network approach. The analysis led to the identification of regulatory genes, called switch genes, involved in the network changes between mutated BRAF papillary carcinomas and normal thyroid tissues. In particular, we identified 227 switch genes. Within the network generated by these genes, 63 were found to be targets of the same microRNA, the mir-335-5p. The role of this microRNA was then investigated through an in vitro study. We selected two primary cell lines and four immortalized lines of thyroid cancer, all of them carrying the BRAF mutation, which showed lower levels of mir-335-5p expression compared with normal control cells. A synthetic microRNA was transfected in all six cell lines. After transfection, the analyses showed an increase in TSHR, PAX8, and NIS expression in the two primary cell lines and in three out of four immortalized lines. Furthermore, all the studied lines showed an increased iodine uptake following treatment with mir-335-5p. Moreover, we obtained organoids by growing the transfected lines in a semi-solid culture medium. We studied the morphology of the 3D structures generated before and after the transfection of miR-335-5p, the interaction among organoid cells and extracellular matrix components, and the protein levels of thyroid-specific genes through immunofluorescence. Our results led us to conclude that the restoration of the intracellular levels of mir-335-5p could have a role in promoting the re-differentiation of thyroid tumors with BRAF mutation.