Previous studies have provided evidence that cigarette smoking plays an important role in epigenetic regulation of oxidative stress genes (e.g., glutamate-cysteine ligase catalytic subunit (GCLC)) and immune-related genes (IL-12RB2 and WIF-1) involved in the pathogenesis of COPD and lung cancer (CCDC37, and MAP1B) [5, 11, 59–61]. The gene discussed is GCLC; the disease is chronic obstructive pulmonary disease.