CD274 and central nervous system cancer: In Zeng's study (Zeng et al., 2016) involving 229 glioma specimens of grade I-IV, no significant correlation between PD-L1 and OS was found in all gliomas, but further analysis revealed a negative correlation between PD-L1 and OS (P = 0.018) if OS > 12 months is set a criterion in grade IV glioma only.