Prognostic value of serum exosomal microRNA-21 for patients with renal cell carcinoma

Background: Renal cell carcinoma (RCC) is the most common malignant cancer in the adult kidney. The aim of this study is to explore the prognostic values of exosomal miR-21 in patients with RCC. Methods: We retrospectively reviewed 62 patients with RCC. The expressions of exosomal miR-21 were detected by real-time PCR. Prognostic factors were evaluated using Kaplan-Meier curves and Cox proportional hazards models. Results: Of all 62 patients with RCC, miR-21 concentration was significantly higher in the exosomes than in the exosome-depleted supernatants and the whole plasma samples (P<0.001), which indicated that miR-21 mostly expressed in the exosomes. Moreover, through Kaplan-Meier survival analysis to compare OS and PFS according to miR-21 expression, we found that patients with low expression of exosomal miR-21 had a significantly better OS (P=0.03) and PFS (P=0.001) than patients with high exosomal miR-21 expression. Multivariable ananlysi showed that low exosomal miR-21 was also a favorable independent risk factor for both OS and RFS. Conclusions: In this study, we found that miR-21 concentration was significantly higher in the exosomes than in the exosome-depleted supernatants and the whole plasma samples. Furthermore, low exosomal miR-21 was also a favorable independent risk factor for both OS and PFS of patients with RCC.