MMP12 and neoplasm: In the CCSP-rtTA/(TetO)7-CMV-MMP12 spontaneous lung tumor mouse model, the average CHI3L1 concentration in BALF of doxycycline-treated mice with tumor was 3-fold higher (159.7±22.4 ng/ml) compared with that in BALF of doxycycline-untreated mice (49.6±22.8 ng/ml, p<0.001, Figure 3A, upper left panel).