Multiple recognition assay reveals prostasomes as promising plasma biomarkers for prostate cancer

Abstract

Prostasomes are microvesicles (mean diameter, 150 nm) that are produced and secreted by normal and malignant prostate acinar cells. It has been hypothesized that invasive growth of malignant prostate cells may cause these microvesicles, normally released into seminal fluid, to appear in interstitial space and therewith into peripheral circulation. The suitability of prostasomes as blood biomarkers in patients with prostate cancer was tested by using an expanded variant of the proximity ligation assay (PLA). We developed an extremely sensitive and specific assay (4PLA) for detection of complex target structures such as microvesicles in which the target is first captured via an immobilized antibody and subsequently detected by using four other antibodies with attached DNA strands. The requirement for coincident binding by five antibodies to generate an amplifiable reporter results in both increased specificity and sensitivity. The assay successfully detected significantly elevated levels of prostasomes in blood samples from patients with prostate cancer before radical prostatectomy, compared with controls and men with benign biopsy results. The medians for prostasome levels in blood plasma of patients with prostate cancer were 2.5 to sevenfold higher compared with control samples in two independent studies, and the assay also distinguished patients with high and medium prostatectomy Gleason scores (8/9 and 7, respectively) from those with low score (≤6), thus reflecting disease aggressiveness. This approach that enables detection of prostasomes in peripheral blood may be useful for early diagnosis and assessment of prognosis in organ-confined prostate cancer.

Time-dependent release of extracellular vesicle subpopulations in tumor CABA I cells

“…Moreover, there is an increasing expectation in their potential use as clinical targets and as diagnostic and prognostic biomarkers since vesicles occur in bloodstream and other biological fluids (e.g., urine, semen, amniotic fluid, saliva, synovial and bronchoalveolar fluid, breast milk, spinal fluid, ascites, malignant and pleural effusion), particularly the ones that are exposed to primary tumors (2,19,(25)(26)(27)(28).…”

Therapeutic and diagnostic applications of extracellular vesicles

“…In this respect, the EV concentration present in serum of tumor-bearing patients was shown to be increased compared to healthy controls [217,[232][233][234][235]. The EV protein abundance also has prognostic value as it was observed that patients with stage III melanoma with a high EV-associated TYRP2 protein burden showed increased risk of disease progression [207].…”

“…Moreover, following resection of the primary tumor, the EV concentration markedly decreased indicating its correlation with tumor presence [235]. However, relying solely on EV concentration lacks specificity as the same observation was made for distinct cancer types [217,[232][233][234][235] and, importantly, for non-disease stimuli (e.g. physical exercise [236]).…”

Exosomal microRNAs in liquid biopsies: future biomarkers for prostate cancer

“…Prostasomes are not only secret by normal prostatic cells but also by neoplastic cells that export prostasomes to the extracellular environment, participating in tumor proliferation and metastasis [49]. Prostasome levels are reportedly increased in prostate cancer patients and these levels are associated with the disease aggressiveness [50]. The development of future isolation techniques for prostasomes found in biological fluids will let to get better insight in the identification and analysis of the protein, lipid and nucleic acids content of them and the potential utility for the diagnosis and prognosis of prostate cancer.…”