Despite the analysis of non-cancer tissues from the specimen, the fact that the lung sections used for immunohistochemical analysis were from patients that underwent lung resection to treat lung cancer might conceal a regulatory effect of COPD or smoking status on CEACAM expression, since CEACAM1, CEACAM5, and CEACAM6 have all been shown to be up-regulated in lung cancer [49-53]. Here, CEACAM6 is linked to cancer.