MicroRNAs constitute a class of small cellular noncoding RNAs (typically 19-23 nt) which function as post-transcriptional regulators of gene expression. The involvement of microRNA in both normal development as well as disease is well established and microRNAs are considered important biomarkers in several diseases including cancer. Surprisingly cell free microRNAs are also found in several biofluids where they have been shown to be very stable, most likely because they are protected from degradation by protein complexes and other particles including exosomes.

Exosomes are nanovesicles secreted into the extracellular environment by a wide range of cell types under normal and pathological conditions. As the profile of exosomal microRNAs may be a fingerprint of the releasing cell type and because they are released in easily accessible body fluids such as blood and urine, their microRNA content holds potential as biomarkers for early detection of malignancy.

We have developed different technologies enabling the detection of prostate cancer microRNA biomarkers in exosomes derived from urine from non-prostate massaged men. The first of these technologies is a highly sensitive LNA™-based qPCR platform for microRNA detection, which enables profiling in biofluids where microRNA levels are extremely low. At this point we have already applied this platform on thousands of biofluid samples including serum/plasma and urine to establish normal reference ranges for circulating microRNAs as well as to identify biomarkers of disease. The second technology is a simple exosome precipitation system which only requires low speed centrifugation to harvest urine exosomes.

Our developed technologies was applied to cell-free urine from three different cohorts including individuals with prostate cancer (PCa) and benign prostate hyperplasia, to identify several differentially regulated microRNAs in urine from PCa bearing individuals. PCa specific signatures were obtained by different combinations of these differentially regulated microRNAs. In conclusion, cell free urine samples holds potential as a liquid biopsy source for exosomal microRNA markers in prostate cancer. Data showing that small miRNA signatures (down to two miRNAs) hold strong diagnostic potential in PCa will be presented.

Citation Format: Thorarinn Blondal, Anne I. Rasmussen, Anni R. Thomsen, Michael Borre, Jacob Fredsøe, Ditte Andreasen, Torben Falck Ørntoft, Karina D. Sørensen, Peter Mouritzen. A microRNA signature in urinary exosomes for diagnosis of prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1943.