High programmed cell death 1 ligand-1 expression: association with CD8+ T-cell infiltration and poor prognosis in human medulloblastoma.

OBJECTIVE Medulloblastoma is a type of malignant tumor arising in the cerebellum. The clinical importance of programmed cell death 1 ligand-1 (PD-L1) expression in medulloblastoma remains unknown. The aim of the present study was to examine the expression of PD-L1 and tumor-infiltrating T cells, and to evaluate their relationships to the prognosis of patients with medulloblastoma. METHODS The authors immunohistochemically analyzed PD-L1 expression and CD3+ and CD8+ lymphocyte infiltrations in tumor specimens from 16 patients with medulloblastoma. RESULTS High expression of PD-L1 was observed in 9 (56.3%) of 16 samples studied. High expression of PD-L1 was associated with low infiltrations of CD3+ or CD8+ lymphocytes. Patients with high expression of PD-L1 had shorter progression-free survival and overall survival times than those with low expression (p = 0.076 and p = 0.099, respectively). In addition, patients with high expression of PD-L1 and with low infiltration of CD8+ lymphocytes had a significantly worse outcome, with a 5-year survival rate of 15%, as compared with the other patients, who had a 5-year survival rate of nearly 90% (p = 0.0048 for progression-free survival and p = 0.010 for overall survival). CONCLUSIONS These findings indicate that PD-L1 expression was associated with a reduced infiltration of CD8+ T cells and poor prognosis in human medulloblastoma.