SPDL1 and central nervous system cancer: To address whether circulating sPD-L1 molecules are directly targeted by an anti-PD-L1 antibody, we performed in vivo studies using the glioma murine model treated with IR (20 Gy), anti-PD-L1 or IR plus anti-PD-L1; we found that there was no difference in baseline sPD-L1 expression levels among the different groups (1.58 ± 0.315 pg/ml, 1.69 ± 0.24 pg/ml, and 1.18 ± 0.51 pg/ml, respectively, P = 0.227; Figures 5A, B).