Comparative analysis of plasma and urinary EV RNA content in prostate cancer patients

Introduction:Recently, EVs have emerged as a very attractive source of cancer-derived RNA biomarkers for the early detection,prognosis and monitoring of cancer progression. However, biofluids contain a complex mixture of EVs derived from various tis-sues and to what extent their RNA cargo reflects the RNA content of cancer cells is unknown. Moreover, a systematic comparisonof RNA cargo in blood and urinary EVs has not been reported before.Methods:EVs were isolated from plasma and urine samples collected before and after the surgery from 10 patients with prostatecancer (PC) and RNAseq libraries were prepared in duplicates. A total of 80 small RNA libraries were constructed from the EV-enclosed RNA. In addition, 40 small RNA and 40 transcriptome libraries were constructed from paired PC and normal prostate
ISEV2021 Abstract Book of tissues. All libraries were sequenced using Illumina’s NextSeq instrument. RNAseq data were analysed using an in-house softwaretool.Results:The most common RNA types in EVs were miRNAs, piRNAs, tRNAs, lncRNAs and mRNAs. The majority of RNAsthat were overexpressed in the tumour tissues were detectable in the pre-operation urinary and/or plasma EVs. The levels of 63mRNAs, 3 lncRNAs, 2 miRNAs and 1 piRNA were significantly decreased in the post-operation urinary EVs thus suggesting thatthe main tissue source of these RNAs in urine is PC and/or normal prostate tissues. These RNAs represent biomarker candidatesfor the development of liquid biopsies for the detection or active surveillance of PC. No such RNA biomarkers were identifiedin plasma EVs. Moreover, both plasma and urinary EVs contained a substantial fraction of exogenous RNAs that are mapped tovarious microbial genomes thus possibly representing a human microbiome.Summary/Conclusion:This study provided new insight into the composition of RNA cargo in plasma and urinary EVs and itscorrelation with PC tissues and revealed a number of RNA biomarkers for the detection and active surveillance of PC.