CONICET | Buscador de Institutos y Recursos Humanos

Metastatic prostate tumor cells have mainly tropism to the bone, triggering the disruption of bone formation/resorption balance. Although several studies have focused on soluble factors as the paracrine signaling between prostate tumor and bone cells, there is increasing evidence on the involvement of extracellular vesicles during the metastatic process. Prostate cancer derived exosomes, which carry diverse biomolecules and are found in body fluids, have been shown to favor tumor progression and may have the potential to emerge as biomarkers in liquid biopsies. Hence, to evaluate whether prostate tumor exosomes prepare the bone metastatic niche by trafficking molecules that modulate bone cell physiology, we co-cultured CFSE-stained PC3 cells with unlabeled preosteoblastic MC3T3 or preosteoclastic Raw264.7 cells. After 48h incubation, CFSE staining was observed in the originally unlabeled bone cells, suggesting an extracellular vesicle trafficking from prostate to bone cells. Next, exosomes were isolated by ultracentrifugation and further characterized by transmission electron microscopy, flow cytometry (anti-CD63 magnetic beads and anti-CD81-PE) and Western Blot (anti-CD81, anti-TSG101 and anti-flotillin-1). The presence of 60-100 nm vesicles containing exosomal markers was confirmed. In addition, we mined RNA-seq and microarray data (GSE109356, GSE117744 and GSE35813) and assessed the exosomal RNA cargos. For further analyses, we selected 16 miRNAs that overlapped in all 3 datasets and were among the 100 most abundant of each study. Gene ontology analysis revealed these 16 miRNAs together with their target mRNAs to be associated with inflammation, bone regeneration, epithelial-mesenchymal transition, cellular adhesion and cancer pathways. Altogether, we showed prostate tumor exosomes trafficking between tumor cell and bone progenitors, and shed light into relevant miRNAs as part of the vesicle cargo that might promote the tumor seeding in the bone.