CTSB inhibited lung metastases in vitro and in vivo . (A) The number of lung metastatic nodules was dramatically reduced in CTSB-shRNA-treated mice compared with controls (a: PBS; b: Lipo; c: NC; d: CTSB-shRNA). (B) The lung weight of mice reached 0.6 ± 0.158, 0.56 ± 0.114, 0.56 ± 0.152, 0.24 ± 0.114 for PBS, Lipo, NC, and CTSB-shRNA, respectively (P < 0.05). The animal experiment was repeated three times. (C) Kaplan-Meier survival curves of tumor-bearing mice demonstrated the treatment of CTSB-shRNA prolonged the survival of mice with lung metastasis (P < 0.01). (D &E) CTSB-shRNA was effective in decreasing the invasive capacity of lung cancer cells (a: PBS; b: Lipo; c: NC; d: CTSB-shRNA). The invasive capacity of lung cancer cells decreased nearly 80% after treatment with CTSB-shRNA by quantitative analysis (P < 0.05).