Next-generation sequencing of circulating exosomal RNA from metastatic castrate-resistant prostate cancer patients.

Abstract

233 Background: PCa has proven to be an extraordinarily complex disease, with both genetic and phenotypic heterogeneity. Exosomes are membranous nano-sized (50-100nm) vesicles derived from both normal and tumor cells, and function in cell-to-cell communication. These vesicles and their nucleic acid cargo may serve as a peripheral biomarker for genetic risk assessment of PCa prognosis and therapeutic response. The goal of this study was to characterize exosome derived RNA (exoRNA) isolated from blood of metastatic CRPC patients. Methods: Blood samples from 18 consented clinically annotated mCRPC patients and 1 normal control; exosomes were isolated with ultracentrifugation and exoRNA extracted. Following library prep, paired-end sequencing was performed using Illumina Hi-Seq 2000. A bioinformatics pipeline was used for data pre-possessing including alignment, duplicate removal, normalization and variant calling. Visualization and differential analyses were performed with SNP & Variation Suite v8.x. Results: Through preliminary analyses we identified 39 genes commonly expressed in the exosomes of these mCRPC patients. These include PDPK1, USP9X, MAGI2, HMGA2 and PTGFR all of which have been previously expressed in prostate cancer. In exoRNA there is evidence of extensive chromosomal rearrangement resulting in a myriad of gene fusions and isoforms. A diverse variety of lcnRNA, ncRNA and miRNA were also identified in circulating exosomes. Differential expression analyses will be presented. PCR validation is ongoing. Conclusions: The identification of PCa associated transcripts in blood derived exosomes provide evidence that exosomes and exosomal cargo may serve as biomarker in CRPC patients. Exosomes and exoRNA may provide otherwise unattainable insight into tumor evolution and disease progression. Additional studies evaluating the clinical relevance and prognostic value of exosomal RNA will be critical for biomarker development.