PDCD1 and osteosarcoma: (55) combined a functional inhibitor of PMN-MDSCs via selectively suppressing PI3Kδ/γ, (S)- (–)-N-[2-(3-Hydroxy-1H-indol-3-yl)-methyl]-acetamide (SNA), with an anti-PD-1 antibody to treat mice bearing osteosarcoma, and they validated that tumor growth was restrained and survival time was prolonged.