Upregulation of Indoleamine 2,3-Dioxygenase 1 in Tumor Cells and Tertiary Lymphoid Structures is a Hallmark of Inflamed Non–Small Cell Lung Cancer

IDO1 pathway in NSCLC is driven by the immune system rather than by tumor cells. Targeting IDO1 in combination with anti-PD-1/PD-L1 might be beneficial only in patients with inflamed tumors and particularly in those bearing TLS.