On combining the in vitro and in vivo results, we revealed that: (i) IRF9 expression was significantly increased in human lung cancer samples; (ii) IRF9 overexpression increased tumor cell proliferation and migration in vitro; (iii) IRF9 silencing decreased tumor cell proliferation and migration in vitro; (iv) VCAN is a direct downstream target of IRF9; (v) IRF9 overexpression increased lung tumor growth in vivo; and (vi) IRF9 silencing reduced lung tumor growth in vivo. This evidence concerns the gene IRF9 and neoplasm.