Our analysis found that significantly greater gene expressions of HAVCR2 and ENTPD1 (but not PDCD1, CTLA4, LAG3, CD160, KLRG1, CD96, BTLA, 2B4, or TIGIT) were observed in glioblastoma compared to normal brain tissue (Figure 1A and Figure S1A), while HAVCR2 and ENTPD1 had the greatest significant differences between glioblastoma (grade IV) and grade II and III glioma of the 11 genes examined (Figure 1B and Figure S1B). Here, PDCD1 is linked to central nervous system cancer.