Could microRNA Analysis Help in the Management of Medullary Thyroid Cancer?

<b>Introduction.</b> In medullary thyroid carcinoma (MTC), calcitonin levels and TNM staging are established prognostic factors. However, the diagnostic accuracy of cytology in MTC is poor. In this context, microRNAs (miRNAs) may be useful as valuable biomarkers, although evidence in MTC remains scarce. The aim of this study was to determine the expression of several miRNAs in patients with MTC and to investigate their association with clinical aggressiveness. <b>Methods.</b> Twenty-five patients undergoing surgery for MTC were included. miRNA expression profiles (miR-183-5p, miR-375-5p, miR-144-3p, miR-34a-5p, and miR-200c-3p) were analyzed in both histological samples of MTC and paired healthy thyroid tissue. cDNA synthesis was performed using the miRCURY LNA RT Kit (Exiqon Ref. 339340 Qiagen, Hilden, Germany). Gene expression was studied by real-time PCR using the QuantStudio 5 kit (Applied Biosystem). Variables included epidemiological, clinical, and follow-up variables. Statistical analysis: SPSS v.29. Kruskal-Wallis, Mann-Whitney U, and Spearman's ρ tests were used. <b>Results.</b> Sixty percent (<i>n</i> = 15) were female and 56% (<i>n</i> = 14) had familial CMT. The mean age at diagnosis was 41.8 years. The median expression of miR-200c-3p, miR-144-3p, miR-34a-5p, miR183-5p, and miR-375-5p was 1.02, 0.923, 1.002, 7.666, and 2.226, respectively. Significant differences in expression were found for miR183-5p and 375-5p (<i>p</i> = 0.001) compared to paired healthy thyroid tissue. Patients with a higher disease-free survival (DFS) showed higher expression of 200c-3p (ρ = 0.456, <i>p</i> = 0.022). <b>Conclusions.</b> The expression of miRNAs 183-5p and 375-5p may help us to diagnose MTC, and a lower expression of miRNA 200C-3p may indicate a higher clinical aggressiveness.