CTLA4 and chronic obstructive pulmonary disease: In addition to the changes in the tumor immune microenvironment, an increased expression of PD-L1 in tumor cells [11, 26], promoter methylation of CTLA4, LAG3, and PD-L1, and an abnormal expression of microRNAs [27–29] can affect the efficacy of ICIs in NSCLC patients with COPD.