In addition, the level of CEACAM5 (P = 0.030), CNGB1 (P = 0.042), CSTL1 (P = 0.046), RASAL1 (P = 0.039), SLC4A3 (P = 0.035) expression were higher in patients with lung cancer coexisting COPD than that in patients with lung cancer alone (Figures 9A–E). Here, SLC4A3 is linked to lung cancer.