PDCD1 and neoplasm: Adjusted by tumor purity (Figure 2G), the ST8SIA1 expression level was also significantly positively associated with the expression of PDCD1 (Rho = 0.699, p < 0.001), CD274 (Rho = 0.271, p < 0.001), CTLA4 (Rho = 0.579, p < 0.001), LAG3 (Rho = 0.711, p < 0.001), HAVCR2 (Rho = 0.217, p = 0.005), TIGIT (Rho = 0.79, p < 0.001), and VSIR (Rho = 0.329, p < 0.001).