PMC

Release of extracellular miRNA in body fluids from various cancer types.

Liquid biopsy is the analysis in biological fluids of circulating cells or other cellular components, such as miRNAs, to provide information on cancer appearance and development in target tissues. The liquid biopsy in oncology may be used for early diagnosis (secondary prevention), cancer staging, prognosis, predicting the response to a specific therapy, evaluating therapy outcome, and patient follow up to individuate early relapses (tertiary prevention).

Urine is emerging as a biological fluid suitable to perform liquid biopsy in a minimally invasive manner, a fundamental attribute for secondary and tertiary prevention of cancer. Several extracellular miRNAs have been isolated in urine. It is possible to analyze miRNAs in voided urine, in urine sediment and urine supernatant. The choice of urine fraction is crucial because the miRNAs isolated are quite different: (a) supernatant contains exosomal miRNAs filtered by glomeruli; (b) sediment also contains microRNAs released by different cell types contained in this urine fraction; (c) voided urine contains both miRNA fractions. Because of this reason, supernatant miRNAs have a high accuracy as biomarker of cancer located outside the genitourinary system than sediment miRNAs. In urine it is possible to identify also prostatic miRNAs, especially after a prostate massage. In the circles we indicate the organs where the miRNAs originate from. In squared boxes we indicate the miRNA typologies and in rounded square boxes we indicate urine typologies. Black arrows indicate total miRNA displacement; grey dashed arrows indicate a partial miRNA displacement, and grey dotted arrows indicate which miRNA typology is more expressed in the different urine fractions.