PDCD1 and central nervous system cancer: Similarly, we also found that the expression of MK3 was significantly positively correlated with PD-1 (r = 0.520, p < 0.001), PD-L1 (r = 0.570, p < 0.001), and CTLA-4 (r = 0.360, p < 0.001) in glioma (Figures 8G–I).