Metabolic reprogramming mediated PD-L1 depression and hypoxia reversion to reactivate tumor therapy.

As a promising cancer treatment, photodynamic therapy (PDT) still achieved limited clinical success due to the severe hypoxia and programmed death ligand-1 (PD-L1) over-expressed immunosuppression tumor microenvironment. At present, few methods have been proven to solve these two defects simply and effectively by a single drug or nano-system simultaneously. To ameliorate this situation, we designed and constructed MB@Bu@MnO2 nanoparticles with two-step oxygen regulation ability and PD-1/PD-L1 axis cascade-disruption capacity via a biomineralization method. In such a nanosystem, manganese dioxide albumin (MnO2@Alb) was used as the drug carrier, Butformin (Bu) as mitochondria-associated oxidative phosphorylation (OXPHOS) disruption agent with PD-L1 depression and oxygen reversion ability, and methylene blue (MB) as PDT drug with programmed cell death protein 1 (PD-1) inhibition capacity. Owing to the tumor-responsive capacity of MB@Bu@MnO2 nanoparticles, Bu and MB were selectively delivered and released in tumors. Then, the tumor hypoxia was dramatically reversed by Bu inhibited oxygen consumption, and MnO2 improved oxygen generation. Following this, the reactive oxygen species (ROS) generation was enhanced by MB@Bu@MnO2 nanoparticles mediated PDT owing to the reversed tumor hypoxia. Furthermore, the immunosuppression microenvironment was also obviously reversed by MB@Bu@MnO2 nanoparticles enhanced immunogenic cell death (ICD) and PD-1/PD-L1 axis cascade-disruption, which then enhanced T cell infiltration and improved its tumor cell killing ability. Finally, the growth of solid tumors was significantly depressed by MB@Bu@MnO2 nanoparticles mediated PDT. All in all, this well-designed nanosystem could solve the defects of traditional PDT via PD-1/PD-L1 axis dual disruption and reversing tumor hypoxia by two-step oxygen regulation.