DPP9 in human liver cancer cells (HepG2 and Huh7) could promote apoptosis and reduce proliferation by inhibiting the EGFR/PI3K/Akt signaling pathway (Yao et al., 2011; Chowdhury et al., 2013), and inhibiting the expression and activity of DPP9 in Huh7 cells could decrease the adhesion and migration ability of cells (Zhang et al., 2015b). This evidence concerns the gene DPP9 and liver cancer.