Zhang et al. (2022) indicated that tanshinone IIA sulfonate might be used as an immunotherapy for colorectal cancer by suppressing IDO1 and TDO2 that promote tumor immune evasion. Ultimately, tanshinone IIA sulfonate enhanced tumor immunotherapy by decreasing Tregs and elevating CD8+ T cells respectively. Overall, tanshinone enhances the cytotoxicity of CD8+ T cells or NK cells, avoiding tumor immune escapes. The mechanism by which it hinders tumor immune evasion is viewed in Figure 6. Here, IDO1 is linked to neoplasm.