HIF1A and hepatocellular carcinoma: These findings are in line with the findings of Tian et al. [23], who reported that the exosomal hsa-miR-21-5p is upregulated in HCC due to the acidic microenvironment and that hsa-miR-21-5p activates HIF-1 and HIF-2, promoting the growth and spread of HCC cells.