Treg cells have an immunosuppressive effect in the TME by inactivating the priming and effector activities of CD4+ and CD8+ T cells.59 Moreover, several reports have confirmed the associations between the density of Treg cells and poor outcome in different types of tumour.91 A recently published report on glioblastoma showed that PTEN deficiency was linked to high macrophage densities.22 Interestingly, the authors of this study found that the density of CD8+ T cells increased in PTEN wild-type tumours after PD1 blockade therapy. The gene discussed is CD8A; the disease is glioblastoma.