SUN-119 Identification of Novel Mirnas Found to Be Differentially Expressed Between ATA Risk Stratification Groups in Papillary Thyroid Carcinoma

The study of miRNAs in PTC has shown that these molecules can help in the diagnosis, prognosis and also as therapeutic candidates [1]. miRNAs are known to be differentially expressed in PTC compared to non-cancerous tissue and a few studies have shown association with some clinico-pathological features. However, little is known regarding their expression in relation to risk of disease progression. In this study, we examined the expression of miRNAs in patients diagnosed with PTC in association with risk of disease recurrence and/or persistence. Patients were classified by three endocrinologists to either high (H) or low (L) risk according to ATA Risk Stratification. PTC tissue was micro-dissected from Formalin Fixed Paraffin Embedded (FFPE) tissue for analysis. OPenArray analysis showed that 21 miRNAs were differentially expressed in H-L groups (n=4/grp). qRT-PCR was used to confirm these differences in a larger cohort of PTC (H=46; L=58). This comparison also included comparisons between cancer and normal tissue and investigation of miRNAs known to be differentially expressed (i.e miRNAs 222, 221 and 146b). All analysis was performed in Rstudio using ΔΔCt relative to expression of miR-16 which was not altered by PTC. By qRT-PCR, only 3 of the 21 miRNAs identified by OpenArray analysis, were differentially expressed in H vs L risk (each P<0.05). These miRNAs are known to be involved in cancer progression pathways but have not been reported in PTC. Individual Receiver Operating Characteristic (ROC) curve analysis of these 3 miRNAs had AUC as follows (miR 1: 0.62, miR 2: 0.62, miR 3: 0.64,) and when analyzed together, the AUC model was improved (AUC=0.76). Examination of cancer vs normal tissue confirmed higher expression miR-146b, miR-221 and miR-222 (each P<0.05). However, these miRNAs were not differentially expressed when H vs L risk were analysed. In this study, we identified 3 miRNAs with potential utility for the stratification of patients into those with H or L risk disease recurrence/persistence. As the current ATA 3-tiered system used is still a reflection of the continuum of risk that patients have, whether these 3 miRNAs may have the utility to further stratify those in the intermediate group remains to be investigated. Reference: 1. Ramírez-Moya, J. and P. Santisteban, miRNA-Directed Regulation of the Main Signaling Pathways in Thyroid Cancer. Frontiers in Endocrinology, 2019. 10: p. 430.