Prognostic relevance of programmed cell death ligand 1 expression in glioblastoma

The aim of this study was to determine the clinicopathological significance of programmed cell death ligand 1 (PD-L1) expression in glioblastoma (GBM). In a retrospective cohort of 115 consecutive patients with GBM, PD-L1 expression was determined using immunohistochemistry (IHC). Membranous and fibrillary PD-L1 staining of any intensity in > 5% neoplastic cells and tumour infiltrating immune cells (TIIs) was considered positive staining. In addition, isocitrate dehydrogenase-1 (IDH-1) (R132H) expression and cluster of differentiation 3 (CD3)-positive T-cell infiltration were investigated using IHC. O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation assay and fluorescence in situ hybridization (FISH) for the assessment of 1p/19q deletion were performed. Expression of PD-L1 in tumour cells and TIIs was found in 37 (32.2%) and 6 (5.2%) patients, respectively. Kaplan-Meier analysis indicated that PD-L1 expression in tumour cells was significantly associated with poor overall survival (OS) (P = 0.017), though multivariate Cox analysis did not confirm this association (hazard ratio 1.204; P = 0.615). PD-L1 expression in TIIs did not correlate with the patient prognosis (P = 0.545). In addition, MGMT methylation and IDH-1 (R132H) expression were associated with a better prognosis (P < 0.001 and P = 0.024, respectively). The expression of PD-L1 was associated with CD3-positive T-cell infiltration (P < 0.001), and IDH-1 wild type status (P = 0.008). A deeper insight into PD-L1 expression could help to ensure the success of future immunotherapy in GBM. Our study suggested that PD-L1 target therapy might be beneficial for PD-L1-expressing GBM patients with a poor prognosis.