Fig. 7.

A possible negative feedback loop to regulate CD8⁺ T cell activation. Upregulation of IDO1 occurs in tumors in response to IFN-γ, which is secreted by activated CD8⁺ T cells, while the expression of IDO1 is increased, CD8⁺ T cell response will be suppressed, resulting in tumor immune evasion and tumor growth. However, miR-448 downregulates IDO1 protein expression, and the feedback of IDO1 to CD8⁺ T cells will be impaired. Thus, the number of CD8⁺ T cells in the tumor microenvironment will be increased, resulting in tumor rejection