It has been suggested that PD-L1 expression, particularly at the invasive front, may be an immune-suppressive mechanism in other cancers.65 However, given that we have demonstrated that PD-L1 expression is generally low in most glioblastomas, other mechanisms are likely to exist for T-cell suppression, particularly in the tumour core where we observed an absence of a correlation between PD-L1 and CD8+ T cells. This evidence concerns the gene CD8A and cancer.