Abstract 3554: miR-139 is associated with improved prognosis in patients with localized prostate cancer

Background: We previously identified a panel of five miRNAs associated with biochemical recurrence and metastasis following prostatectomy based on NGS-based whole miRNome discovery and qPCR-based validation analysis. In this analysis, we examine the effect of miR-139-5p, one of the down-regulated miRNAs identified in the panel, in greater detail. Methods: Using a cohort of 585 patients treated with radical prostatectomy, we examined the prognostic significance of miR-139 (dichotomized around the median) using the Kaplan Meier method and Cox proportional hazard models. We validated these results using The Cancer Genome Atlas (TCGA) data. We created cell lines that over-expressed miR-139 or transiently transfected cells using miR-139 mimics for functional assays. Finally, we examined pathways through which miR-139 may function using prediction algorithms and confirmed targets by Western blotting and reporter assays. Results: MiR-139 down-regulation was significantly associated with a variety of accepted prognostic factors in prostate cancer, including Gleason score, pathologic stage, margin positivity and lymph node status. MiR-139 was associated with prognosis: the cumulative incidence of biochemical recurrence and metastasis were significantly lower among patients with high miR-139 expression (p=0.0004 and 0.038, respectively). After adjusting for known prognostic factors, patients with high miR-139 expression had significantly lower risk of recurrence (HR 0.77, 95% 0.58-1.04). Validation in the TCGA dataset showed a significant association between dichotomized miR-139 expression and biochemical recurrence (OR 0.52, 95% CI 0.33-0.82). Over-expression of miR-139 in prostate cancer cells led to a significant reduction in cell proliferation and migration compared to control cells, with cells arrested in G2 of cell cycle. IGF1R, RUNX1 and AXL were identified as potential gene targets of miR-139 based on their association with prostate cancer growth pathways and multiple miRNA binding site prediction tools. The reporter assays using luciferase gene constructs containing the predicted miRNA targeting sequence from IGFR1 and RUNX1 verified them as direct targets of miR-139. Furthermore, Western blotting of prostate cancer cells demonstrated RUNX1 and AXL expression were inhibited by miR-139 treatment, which was reversed by addition of miR-139 antagomir. Examination of the molecular mechanism of growth inhibition by miR-139 revealed the downregulation of activated Akt and cyclin D1, with upregulation of the CDK inhibitor p21. Conclusions: miR-139 is associated with improved prognosis in patients with localized prostate cancer, which may be mediated through inhibition of IGF1R, RUNX1 and/or AXL and their associated growth signaling pathways. Citation Format: Tania Benatar, Robert K. Nam, Elizabeth Kobylecky, Yutaka Amemiya, Arun K. Seth. miR-139 is associated with improved prognosis in patients with localized prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3554.