IDO1 and neoplasm: Interestingly, these 53 upregulated genes, summarized by the GSVA as a signature of BAL cells from tumor-bearing lung segments, showed moderately high correlations with the gene expressions of multiple checkpoint proteins (Figure 5B), including PD-1/PDCD1 (r = 0.59, p = 0.0078), CTLA4 (r = 0.62, p = 0.0046), TIM-3/HAVCR2 (r = 0.56, p = 0.0130), LAG3 (r = 0.51, p = 0.0260), IDO1 (r = 0.43, p = 0.0660), and TIGIT (r = 0.52, p = 0.0220), where similar correlations, except for that with CTLA-4, were also noted in the published microarray datasets (Figure S6A in Supplementary Material).