In particular, the main aim of the study will be to highlight differences between bone and skeletal muscle microenvironments, which are respectively preferential and non-preferential metastasisation sites for breast cancer cells, in order to identify specific pathways driving breast cancer cells extravasation. To this purpose, differences in the transcriptional profile of ECs derived from bone and muscle endothelium will be investigated. These analyses will be used to select target genes differentially expressed by bone- and muscle-specific ECs. Then, ECs obtained from bone and muscle endothelium will be respectively used to mimic bone and muscle microvessel environments in microfluidic in vitro 3D models allowing for the study of breast cancer cell extravasation. The genes selected according to the results of the transcriptomic analysis (e.g. genes expressed in ECs derived from bone endothelium, but not expressed in ECs derived from muscle endothelium) will be silenced and the effect of gene silencing will be evaluated monitoring breast cancer cell extravasation in order to verify the involvement of the selected genes in this process.