The level of CEACAM5 (P < 0.001), CNGB1 (P < 0.001), CSTL1 (P < 0.001), RASAL1 (P < 0.001), SLC4A3 (P < 0.001) expression were also increased in lung tissues of patients with lung cancer coexisting COPD compared to controls. Here, CEACAM5 is linked to lung cancer.