CD274 and neoplasm: Harnessing the crucial role of L-arginine in anti-tumor T cell responses and its synergistic effect with PD-L1 blockade, an engineered EcN strain was developed by deletion of the arginine repressor (ArgR), proficient in colonizing tumors and converting ammonia to L-arginine.644 The metabolism of the tumor microenvironment can be effectively regulated by these engineered bacteria, leading to improved outcomes of immunotherapy.