PDCD1 and neoplasm: Considering the tumor population, several correlations were observed between serum VISTA levels and distinct immune checkpoint molecules, such as serum PD-1 (p < 0.0001, r = 0.6523; Figure 3A) and PD-L1 (p < 0.0001, r = 0.7434; Figure 3B) levels [19], serum CTLA-4 (p < 0.0001, r= 0.6136; Figure 3C) levels [22] and serum LAG-3 p = 0.0002, r = 0.5336; Figure 3D) levels.