To decipher how IRG1 expression is induced in TAMs, we cocultured mouse bone marrow–derived macrophages (BMDMs) with different types of syngeneic tumor cells or treated BMDMs with tumor cell–conditioned medium (TCM) and found that either treatment led to Irg1 induction and ITA accumulation (to millimolar level) in BMDMs (fig. Here, ACOD1 is linked to neoplasm.