TNFSF12 and chronic obstructive pulmonary disease: TWEAK expression was also measured by western blot analysis, whereby it was observed that levels of TWEAK in the COPD model group were significantly higher than that in the control group (0.8910 ± 0.0512 vs. 0.5803 ± 0.0733, respectively, P < 0.05; Fig. 3c).