Consistent with our previous results, overexpression of circulating sPD-L1 occurred in glioma patients (median: 0.5594 ng/mL, range: 0–1.4235 ng/mL), while the concentrations were notably lower in HCs (0.1107, 0–0.5908, p < 0.001) and meningioma patients (0.0688, 0.0454–1.4117, p < 0.001) (Figure 1A). Here, SPDL1 is linked to central nervous system cancer.