HIF1A and glioma: Setting aside the specific role of hypoxia in triggering changes in HIF1α and/or HIF2α expression, hypoxia has also been reported to selectively upregulate programmed death-ligand 1 (PD-L1) on myeloid-derived suppressor cells (MDSCs) and macrophages in the TME, allowing glioma cells to escape immune checkpoints (14).