Therefore, we further investigated cytotoxic lymphocytes (CD8+ T cells and natural killer [NK] cells) in human HCC tissues, and the number of cytotoxic lymphocytes significantly reduced in HBV‐infected HCC tissues, which expressed BMP9 at lower levels, compared with HBV‐uninfected HCC tissues (Figure 3C,D). This evidence concerns the gene GDF2 and hepatocellular carcinoma.