First, pro-inflammatory enzyme cyclooxygenase-2 (COX-2) is expressed and active during involution, and correlations between COX-2 expression and PD-L1 expression have been reported in lung cancer, melanoma, a mouse model of mammary cancer, and in tumor-associated macrophages and myeloid derived suppressor cells (55–59). This evidence concerns the gene PTGS2 and lung cancer.