IDO2 and neoplasm: In the context of the tumor immunophenotype, a pan-cancer analysis of IDO2 in the TCGA transcriptomic datasets revealed IDO2 mRNA expression to be strongly associated with high infiltration of immune cells in the tumor microenvironment, as well as tumor mutational load (TMB), microsatellite instability (MSI), mismatch repair (MMR), and immune checkpoint related genes (51).