MicroRNAs (miRs) are small non-coding RNA molecules, which are involved in the development of various malignancies, including prostate cancer (PCa). miR-17-5p is considered the most prominent member of the miR-17-92 cluster, with an essential regulatory function of fundamental cellular processes. In many malignancies, up-regulation of miR-17-5p is associated with worse outcome. In PCa, miR-17-5p has been reported to increase cell proliferation and the risk of metastasis. In this study, prostatectomy specimens from 535 patients were collected. Tissue microarrays were constructed and in situ hybridization was performed, followed by scoring of miR-17-5p expression on different tumor compartments. High expression of miR-17-5p in tumor epithelium was associated with biochemical failure (BF, p < 0.001) and clinical failure (CF, p = 0.019). In multivariate analyses, high miR-17-5p expression in tumor epithelial cells was an independent negative prognostic factor for BF (HR 1.87, 95% CI 1.32–2.67, p < 0.001). In vitro analyses confirmed association between overexpression of miR-17-5p and proliferation, migration and invasion in prostate cancer cell lines (PC3 and DU145). In conclusion, our study suggests that a high cancer cell expression of miR-17-5p was an independent negative prognostic factor in PCa.

Objective: assessing the prognostic role of miR-20a-5p, in terms of clinical outcome, in a large multi-institutional cohort study. Methods: Tissue microarrays from 535 patients’ prostatectomy specimens were constructed. In situ hybridization was performed to assess the expression level of miR-20a-5p in different tissue subregions: tumor stroma (TS) and tumor epithelium (TE). In vitro analysis was performed on prostate cancer cell lines. Results: A high miR-20a-5p expression was found negatively in association with biochemical failure in TE, TS and TE + TS (p = 0.001, p = 0.003 and p = 0.001, respectively). Multivariable analysis confirmed that high miR-20a-5p expression in TE independently predicts dismal prognosis for biochemical failure (HR = 1.56, 95% CI: 1.10–2.21, p = 0.014). Both DU145 and PC3 cells exhibited increased migration ability after transient overexpression of miR-20a-5p, as well as significant elevation of invasion in DU145 cells. Conclusion: A high miR-20a-5p expression in tumor epithelium is an independent negative predictor for biochemical prostate cancer recurrence.