Expression of Homo Sapiens (Hsa)-miR-139-5p as a Clinically Feasible Prognostic Marker for Differentiated Thyroid Cancer

Prognostic uncertainty often leads to overtreatment of differentiated thyroid cancer (DTC) or unspecific management of more aggressive entities. MiR-139-5p (miR-139-5p) has emerged as a promising prognostic factor that may enhance current individual risk assessment systems. Therefore, we aimed to validate miR139-5p expression as a prognostic marker in DTC using a standardized method and to establish expression cutoff values for discriminating prognostic groups. In addition, we explored an in situ approach to analyze this microRNA expression as a potential molecular tool for clinical practice. We collected a tissue series of 132 samples, including thyroid tumors, adjacent normal thyroid tissue, and lymph node metastases from a long-term follow-up retrospective cohort of 60 patients with DTC with either progressive/persistent disease or an excellent response to primary treatment. We first identified recurrent tumor driver mutations and TERT promoter mutations using next-generation sequencing. Through a standardized paired tumor/normal qPCR analysis, we confirmed a significant reduction in miR139-5p expression in progressive/persistent DTCs compared with excellent response DTCs (P value = .002). Further analysis, including thyroid cancer The Cancer Genome Atlas tumor/normal pairs (n = 59), showed a strong association between reduced miR139-5p expression and TERT promoter mutations (P < .001), as well as advanced local or distant metastasis at diagnosis (P = .031). Next, we established miR139-5p^HIGH and miR139-5p^LOW tumor/normal cutoff values to discriminate prognostic groups, with high expression predicting excellent response and low expression predicting disease progression/persistence. Cutoff values were defined through logistic regression and receiver operating characteristic curve analysis and validated in an independent cohort (n = 38). Quantitative image analysis using QuPath software of an automatic chromogenic in situ hybridization assay for miR139 detection further supported the qPCR findings and revealed heterogeneous intratumor miR139 expression, which was lowest in the Ki-67 proliferation index--positive foci. Overall, our data indicate that miR139 expression assessment is a feasible tool for clinical use, potentially reducing overtreatment during primary DTC interventions and supporting a risk-adjusted follow-up schedule.