Characterisation of Castration-Resistant Cell-Derived Exosomes and Their Effect on the Metastatic Phenotype.

Background/objectives: Prostate cancer (PCa) is characterised by its progression to a metastatic and castration-resistant phase. Prostate tumour cells release small extracellular vesicles or exosomes which are taken up by target cells and can potentially facilitate tumour growth and metastasis. The present work studies the effect of exosomes from cell lines that are representative of the different stages of the disease on the tumoral phenotype of PC3 cells.

Methods: Exosomes were isolated by ultracentrifugation from human prostate epithelial cells (RWPE-1) and androgen-dependent PCa cells (LNCaP) and castration-resistant PCa cells (CRPC) with moderate (DU145) or high (PC3) metastatic capacity. The biophysical and biochemical properties of the exosomes were characterised as well as their effects on PC3 cell viability and migration.

Results: The study of the exosomes of prostate cell lines shows heterogeneity in their size, presenting in some of them two types of populations; in both populations, a larger size in those derived from PC3 cells and a smaller size in those derived from non-tumourigenic prostate cells were detected. Differences were found in the physical properties of those derived from healthy and PCa cells, as well as between cells representative of the most aggressive stages of the disease. The highest gamma-glutamyl transferase (GGT) activity was observed in androgen-dependent cells and differences in the pro-metalloproteinases (MMP) activity were detected in healthy cells and in castration-resistant cells with moderate metastatic capacity with respect to PC3 cells. The treatment of PC3 cells with their own exosomes increased PC3 cell viability and migration.

Conclusion: Exosomes represent a promising field of research in the diagnosis, prognosis, and treatment of prostate cancer.