Western blot analysis results displayed that EV markers CD9, CD81, and Alix were not expressed or weakly expressed in osteosarcoma cells, but were highly expressed in EVs, while endoplasmic reticulum membrane protein Calnexin was robustly induced in osteosarcoma cells, but not expressed or expressed very little in EVs (Fig. 2E and Supplementary Fig. 1A). This evidence concerns the gene CD81 and osteosarcoma.