On the other hand, the inefficient killing of tumor cells is mostly due to a direct effect of EGFR-mutated lung cells through the over-production of negative modulators of immune cells including tumor necrosis factor-β (TGF-β), interleukin-10 (IL-10), vascular endothelial growth factor (VEGF), indolamine 2,3-dioxygenase (IDO), C-C chemokine ligand 2 (CCL-2), arginase (ARG)-1, and adenosine. This evidence concerns the gene IDO1 and neoplasm.