CD63 and hepatocellular carcinoma: We extracted the exosomes secreted from HCC cells and found that the level of total exosomal protein, exosome markers (CD9, CD63, HSP70 and TSG101) and extracellular vesicle proteins (CD81, ERBB2 and HLA-A) was obviously decreased when PRR34-AS1 was downregulated (Fig. 4A–D).