CTSK and chronic obstructive pulmonary disease: Of the top 15 most significantly up-regulated genes upon cigarette smoke exposure in the murine model, 7 were also found to be significantly up-regulated in the lungs of COPD patients (MMP12, SPP1, CCL22, ITGAX, GPNMB, CTSK, and CD68; Figure 1D–J), 5 genes were not significantly elevated (CD177, LCN2, SLC6A20, CYP1A1, and MSR1; Supplementary Figure S1), while the 3 remaining genes (Wfcd17, Clec4n, and Ms4a7) or their human orthologs were not present in the database.