Galectin-9 triggers the expansion of CD4+ CD25+ forkhead box P3 (FOXP3)+ CD127 (low) regulatory T cells (Tregs), the contraction of CD4+ effector T cells, and the apoptosis of CTLs in the HCC immune microenvironment, thereby promoting HCC development (16). The gene discussed is FOXP3; the disease is hepatocellular carcinoma.