The tumor volume (TNFR2 KO, 79.10 ± 10.86; BDNF injected TNFR2 KO, 155.78 ± 17.62 mm3, Fig. 7A) and weight (TNFR2 KO, 31.75 ± 11.27 mg; BDNF injected TNFR2 KO, 65.00 ± 13.22 mg, Fig. 7B) in BDNF injected TNFR2 KO mice xenografted with A549 lung cancer cells were significantly higher compared with the TNFR2 KO mice xenografted with A549 lung cancer cells. This evidence concerns the gene BDNF and lung cancer.