Fig. 4

The effects of lung cancer metabolism on immune cells within the tumor microenvironment (TME). Cancerous TME develop in lungs, lacking glucose and tryptophan, while immune-suppressive molecules such as lactate and kynurenine accumulate. In the tumor microenvironment, the high levels of lactate inhibit the tumor immune responses by (1) polarizing macrophages toward the suppressive M2 phenotypes, as well as (2) preventing monocyte migration and dendritic cell differentiation. (3) The presence of excessive lactate also inhibits the function of CD8+ T cell directly. Besides kynurenine, tumors are also known to repress T-cell activity, as is tumor-induced tryptophan deficiency and glucose deprivation. Figure created using BioRender.com