“…Increasing studies have indicated that tumor necrosis factor-alpha (TNF-α) plays a key role in the progression of COPD, where elevated TNF-α levels have been detected in sputum, bronchoalveolar lavage fluid, and bronchial biopsies of COPD patients (Keatings et al, 1996;Mueller et al, 1996;Sun et al, 1998). Several single nucleotide polymorphisms, such as -238G/A, -308G/A, -376G/A, -863C/A, +489G/A, -857T/C, and -1031T/C, have been identified in the TNF-α gene, which is located in the class III region of the major histocompatibility complex on chromosome 6, the most polymorphic region of the human genome (Brogger et al, 2006;Papatheodorou et al, 2007;Trajkov et al, 2009;Cordoba-Lanus et al, 2011). Among the above-mentioned polymorphisms, -308G/A was the best studied, and the role of increasing COPD risk of the A allele in this polymorphism was identified in Asians (Kuçukaycan et al, 2002;Hegab et al, 2005;Hsieh et al, 2008;Zhan et al, 2011;Zhang et al, 2011).…”