Investigation of plasma exosomal miRNA as a biomarker and its potential function in prostate cancer castration resistant development

Prostate cancer (PCa) ranks as the second most frequent cancer and the fifth leading cause of cancer death in men worldwide. Androgen-deprivation therapy is the principal treatment for locally advanced and metastatic disease. Although a majority of patients initially respond well to ADT, most will progress to castration-resistant prostate cancer (CRPC), which contributes to the majority of PCa deaths. Exosomes are small vesicles that contain numerous molecular constituents, including lipids, proteins, RNAs and DNAs, and can mediate cell-cell communications. The aim of this study is to identify plasma exosomal miRNAs correlated with CRPC development, which may serve as a biomarker to monitor disease status and may reveal new role of exosome in CRPC development. Next-generation sequencing (NGS) of plasma exosomal miRNAs was performed in 24 treatment-naive PCa patients and 24 CPRC patients. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to validate candidate miRNAs in 108 treatment-naive PCa patients and 42 CRPC patients and a group of 38 non-CRPC patients under hormone therapy (treated non-CRPC). To study the miRNA function, hormone-dependent PCa cell line LNCaP was cultured in hormone-depleted media. MiRNA was overexpressed by transient transfection of miRNA mimic. Post transfection, transwell assays and cell viability assays were performed to determine the effect of miRNA on cell migration and proliferation. RNA NGS generated an average of approximately 5-million reads per sample and identified differentially expressed miRNAs. QRT-PCR validation showed six miRNAs were significantly differentially expressed between treatment-naïve PCa and CRPC (p-value<0.05). It also showed that five of these miRNAs were differently expressed in CRPC compared treated non-CRPC patients (p-value<0.001). When receiver operating characteristic curve was applied, one of the exosomal miRNAs, miR-423-3p, achieved area under the curve (AUC) = 0.784 when predicting CRPC from treatment-naïve PCa and AUC = 0.883 when predicting CRPC from treated non-CRPC. Overexpression of miR-423-3p had no effect on LNCaP proliferation, but significantly increased cell migration. This study demonstrated that plasma exosomal miRNAs play important roles in CRPC development and may serve as a biomarker for CRPC occurrence prediction.Citation Format: Tianyu Guo, Yang Wang, Xueying Mao, Lei Xu, Jacek Marzec, Edwina Burke, Glenda Scandura, Elzbieta Stankiewicz, Caitlin R. Davies, John Hines, Greg Shaw, Jonathan Shamash, Daniel Berney, Prabhakar Rajan, Karen Tipples, Alistair Grey, Yong-jie Lu. Investigation of plasma exosomal miRNA as a biomarker and its potential function in prostate cancer castration resistant development [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 2580.