Exosomes are small double lipid membrane vesicles (typically 30-200 nm in diameter) that are secreted from all cells. Exosomes encapsulate a portion of the parent cell cytoplasm and are shed into various biofluids, such as blood, CSF and urine.
Exosomes are a rich source of cellular protein, DNA and RNA and are particularly promising for profiling RNA expression from tumor cells as they are highly representative of their cell of origin and serve as a protective environment for mRNA during sample processing.
For EPI, advanced purification techniques are used to isolate exosomes and RNA from “first-catch” (approximately 15 mLs) urine specimens without the need for a prior digital rectal exam (DRE). The EPI gene signature and score incorporates levels of the PCA3 (PCa antigen 3) Prostate Cancer Antigen 3], ERG (v-ets erythroblastosis virus E26 oncogene homologs) and SPDEF (SAM-pointed domain-containing Ets transcription factor)