Figure 4.

Tumor-derived exosomes are secreted via a constitutive/inducible pathway that can be activated by a p53-mediated response. Through this pathway (and possibly additional ones that remain unknown), exosomes can transport microRNAs into the vascular system and regulate important cellular processes such as immunosurveillance, apoptosis and angiogenesis. For example: (a) TP53 can induce the activity of TSAP6 proteins, thereby modulating key functions associated with tumor-derived exosome trafficking. Exosomes are generated by reverse budding of the membrane of multivesicular bodies (MVBs) that fuse with the plasma membrane, causing the release of these particles outside the cell. (b) From this moment on, exosomes enter the vascular or lymphatic system and circulate freely until they bind to their specific target. (c) The release from the cell is possible after the membrane is stimulated by calcium ionophores or phorbol esters. Inositol 3-kinase inhibitors can inhibit this process