Kozuma Y, et al. - Experts gauged the association between indoleamine 2,3-dioxygenase 1 (IDO1) expression in lung adenocarcinoma and clinicopathological features and patient prognosis, including the expression of programmed cell death-ligand 1 (PD-L1). An aggressive form of lung adenocarcinoma may be defined with IDO1 and PD-L1 co-expression. In lung adenocarcinoma cell lines, both proteins were upregulated by treatment with interferon-γ and transforming growth factor-β. In multivariate analysis, findings suggested a significant association of co-expression of IDO1 and PD-L1 with shorter disease-free survival and overall survival.