Tumor-Derived Exosomal Long Noncoding RNAs as Promising Diagnostic Biomarkers for Prostate Cancer.

BACKGROUND/AIMS: Exosomal circulating long non-coding RNAs (lncRNAs) in blood are emerging as clinically useful and non-invasive biomarkers for tumor diagnosis. However, normal cells can also secrete exosomes, so it is a prerequisite to obtain tumor-derived exosomes for better understanding of their diagnostic impacts in cancer. In this study, a dual-antibody-functionalized immunoaffinity system was established to isolate exosomes and investigate their lncRNAs expression pattern and clinical significance in prostate cancer (PCa). METHODS: A commercially available kit was used to isolate total exosomes, which were then purified by a dual-antibody-functionalized immunoaffinity system. RT-qPCR was performed to detect the expression of exosomal lncRNAs. Receiver operating characteristic (ROC) curves were plotted to assess the diagnostic value. RESULTS: Expression levels of two lncRNAs in tumor-derived exosomes were significantly higher than those in total exosomes. The levels of SAP30L-AS1 were upregulated in benign prostatic hyperplasia (BPH), and SChLAP1 levels were significantly higher in PCa than in BPH and healthy individuals. The area under the ROC curve indicated that SAP30L-AS1 and SChLAP1 had adequate diagnostic value to distinguish PCa from controls. Two lncRNAs separately combined with prostate specific antigen (PSA) possessed a moderate ability for discrimination. SAP30L-AS1 expression level was related to PSA values and tumor invasion. SChLAP1 expression was significantly higher in patients with higher Gleason scores, and was also effective in differentiating between BPH and PCa when the concentration of PSA was in the gray zone. CONCLUSION: The isolation of tumor-derived exosomes by dual-antibody-functionalized immunoaffinity systems and detection of their lncRNAs in plasma may lead to the identification of suitable biomarkers, with potential diagnostic utility.