In vivo tumor xenograft mouse model

BALB/c nude mice (Institute of Zoology, Chinese Academy of Sciences) that were 4–6 weeks old were challenged subcutaneously with lung cancer A549 cells modified with a control lentiviral construct (A549shmock) and those modified to express TOPK-targeted shRNA (A549shTOPK) (1×10⁷) to allow tumor development. When palpable tumors (approximately 100 mm³) arose, the mice in each group were randomly allocated to treatment groups of five animals: (1) no treatment (control) or (2) gefitinib (25 mg/kg/d) by oral gavage. Tumor growth was monitored by caliper measurements of the two perpendicular diameters every 3 days, and the volume of the tumor was calculated with the formula V = (width²×length/2). All procedures were performed in compliance with the Regulations for the Administration of Affairs Concerning Experimental Animals (approved by the State Council of the People's Republic of China) and were approved by the Experimental Animal Ethics Committee of Fourth Military Medical University.