Longitudinal evolution of the immune suppressive glioma microenvironment in different synchronous lesions during treatment

The role of immune suppression in glioma progression has been clearly established.1 We and others have recently demonstrated that myeloid cells play a major role in the tumor microenvironment of glioblastoma (GBM) patients,2,3 and that not only bone marrow-derived macrophages (BMDMs) have a higher intrinsic immune suppressive ability compared to resident microglial cells (MG), but also that this ability greatly increases going from the periphery to the tumor core.3 In lower grade gliomas (grades II and III), a much lower amount of BMDM is present, devoid of immune suppressive ability.3 We present here a longitudinal analysis of the immune infiltrate in a patient with a synchronous occurrence of GBM in the left temporal lobe, and a low-grade glioma (LGG) in the right frontal lobe, with discordant isocitrate dehydrogenase (IDH)-mutational status,4 followed by two GBM relapses.