SPDL1 and central nervous system cancer: sPD-L1 is associated with a higher histological tumor grade/stage of cancer in patients with gastric cancer [50], hepatocellular carcinoma [69, 71], glioma [20, 22], nasopharyngeal carcinoma [55], triple-negative breast cancer [64], renal cell carcinoma [72], and clear cell renal cell carcinoma [41].