CD274 and central nervous system cancer: In the recurrent samples, low-grade gliomas expressed PD-1 and PD-L1 in 5 (62.5%) and 4 (50.0%), respectively, of the patients, whereas they were expressed in 21 (63.6%) and 26 (76.5%), respectively, of the patients with recurrent high-grade gliomas (Figure 2).