CD81 and prostate cancer: Because it had a direct association with several exosome markers, such as CD9, CD81 and CD82, we carried out exosome extraction and analysis for the prostate cancer cell lines PC3 and Du145 cells with EWI‐2 CRISPR/Cas9 knockout (Fig. 1A,B,E) as well as the overexpression of EWI‐2 in PC3 cells (Fig. 1E).