SMAD3 and hepatocellular carcinoma: In addition, exosomal circGSE1 secreted by hepatocellular carcinoma cells (HCC) can induce the expansion of Treg cells by regulating the miR-324-5p/TGFBR1/Smad3 pathway, which promotes the secretion of immunosuppressive factors, inhibits the function of CD8+ T cells, and causes tumor immune escape (Huang et al., 2022).