Prostate-Specific Membrane Antigen (PSMA)-Positive Extracellular Vesicles in Urine-A Potential Liquid Biopsy Strategy for Prostate Cancer Diagnosis?

All cells release extracellular vesicles (EVs) to communicate with adjacent and distant cells. Consequently, circulating EVs are found in all bodily fluids, providing information applicable for liquid biopsy in early cancer diagnosis. Studies observed an overexpression of the membrane-bound prostate-specific membrane antigen (PSMA) on prostate cancer cells. To investigate whether EVs derived from communicating prostate cells allow for reliable conclusions on prostate cancer development, we isolated PSMA-positive, as well as CD9-positive, EVs from cell-free urine with the use of magnetic beads. These populations of EVs were subsequently compared to CD9-positive EVs isolated from female urine in Western blotting, indicating the successful isolation of prostate-derived and ubiquitous EVs, respectively. Furthermore, we developed a device with an adapted protocol that enables an automated immunomagnetic enrichment of EVs of large sample volumes (up to 10 mL), while simultaneously reducing the overall bead loss and hands-on time. With an in-house spotted antibody microarray, we characterized PSMA as well as other EV surface markers of a prostate cohort of 44 urine samples in a more simplified way. In conclusion, the automated and specific enrichment of EVs from urine has a high potential for future diagnostic applications.

Compromised repair of radiation-induced DNA double-strand breaks in Fanconi anemia fibroblasts in G2.

Fanconi anemia (FA) is a rare chromosomal instability syndrome with various clinical features and high cancer incidence. Despite being a DNA repair disorder syndrome and a frequently observed clinical hypersensitivity of FA patients towards ionizing radiation, the experimental evidence regarding the efficiency of radiation-induced DNA double-strand break (DSB) repair in FA is very controversial. Here, we performed a thorough analysis of the repair of radiation-induced DSBs in G1 and G2 in FA fibroblasts of complementation groups A, C, D1 (BRCA2), D2, E, F, G and P (SLX4) in comparison to normal human lung and skin fibroblasts. γH2AX, 53BP1, or RPA foci quantification after X-irradiation was combined with cell cycle markers. Cytogenetic analyses were performed on first metaphases after irradiation in G1 and by premature chromosome condensation after exposure in G2. Furthermore, the role of canonical-NHEJ and alternative-NHEJ for the fidelity of the repair of radiation-induced DSBs was examined. In FA fibroblasts, DSB repair was normal in G1 but compromised and more error-prone in the slow repair component of G2 as suggested by higher yields of radiation-induced γH2AX and 53BP1 foci as well as chromatid exchanges. However, RPA foci quantification in G2 indicated proficiency for homology-directed repair of DSBs in FA except for FA D1 (BRCA2). In lung fibroblasts, DSB repair in G1 was conducted with normal kinetics but elevated chromosome exchanges compared to skin fibroblasts. The overall repair of radiation-induced DSBs and the formation of chromosome exchanges in normal and FA fibroblasts in G1 and G2 were governed by canonical-NHEJ with no contribution of alternative-NHEJ. Together, we show impaired repair of radiation-induced DSBs in various FA complementation groups in the slow repair component of G2 that might promote the formation of potentially oncogenic aberrations and clinical radiation hypersensitivity.