miR-221/222 cluster expression improves clinical stratification of non-muscle invasive bladder cancer (TaT1) patients' risk for short-term relapse and progression.

Clinical heterogeneity of bladder cancer prognosis requires the identification of bladder tumors' molecular profile to improve the prediction value of the established and clinically used markers. In this study, we have analyzed miR-221/222 cluster expression in bladder tumors and its clinical significance for patients' prognosis and disease outcome. The study included 387 tissue specimens. Following extraction, total RNA was polyadenylated at 3'-end and reversed transcribed. SYBR-Green based qPCR assays were performed for the quantification of miR-221/222 expression. Extensive statistical analysis was completed for the evaluation of miR-221/222 cluster's clinical significance. The expression of miR-221/222 is significantly downregulated in tumors compared to normal urothelium, while ROC curve and logistic regression analysis highlighted cluster's discriminatory ability. However, miR-222 levels were increased in muscle-invasive (T2-T4) compared to superficial tumors (TaT1), and in high compared to low-grade tumors. Kaplan-Meier survival curves and Cox regression analysis revealed the stronger risk of TaT1 patients overexpressing miR-222 for disease short-term relapse and progression following treatment. Moreover, multivariate Cox models highlighted the independent prognostic value of miR-222 overexpression for TaT1 patients' poor prognosis. Finally, the analysis of miR-222 expression improved significantly the positive prediction strength of the clinically used prognostic markers of tumor stage, grade, EORTC risk-stratification and recurrence at the first follow-up cystoscopy for TaT1 patients' outcome, and resulted to higher clinical net benefit following decision curve analysis. In conclusion, the expression of miR-221/222 cluster is deregulated in bladder tumors and miR-222 overexpression results to a superior positive prediction of TaT1 patients' short-term relapse and progression.