In order to evaluate the feasibility of our tetraspanin-based cathepsin B-targeting strategy, as a first step we expressed CD9/CD63/CD81-RFP CS/NACS recombinant constructs in 5637 cancer cell line, characterized by high cathepsin B expression level, and compared the 3 resulting phenotypes in terms of fluorescence pattern, amount of protein produced with respect to basal, and amount of protein sorted into the EV fraction (Figure 2). This evidence concerns the gene CD63 and cancer.