TNF and chronic obstructive pulmonary disease: As early as 2009, Smolonska et al. [8] conducted meta-analyses about 20 polymorphisms in 12 genes and demonstrated that three polymorphisms in TGF-β1 (rs2241712, rs1982073, and rs6957) were significant with COPD risk in the “diverse populations.” Another three polymorphisms were reported significantly only in Asians (IL1RN rs2234663, TNF-α rs1800629, and GSTP1 rs1695).