Journal Club: Transfer of microRNA via Macrophage-Derived Extracellular Vesicles Promotes Proneural-

Proneural-to-mesenchymal transition (PMT) is a common process in glioblastoma (GBM)49 progression that leads to increased radiotherapy resistance. However, the mechanism50 underlying PMT is poorly understood. Here, we found that tumor-associated macrophages51 (TAMs) triggered PMT in glioma stem cells (GSCs) via small extracellular vesicles (sEVs). sEVs from monocyte-derived macrophages transferred miR-27a-3p, miR-22-3p and miR-221-3p to GSCs, and these microRNAs (miRs) promoted several mesenchymal (MES) phenotypes in proneural(PN) GSCs by simultaneously targeting CHD7. We found that CHD7 played a critical role in the maintenance of the PN phenotype and CHD7 knockdown significantly promoted PMT in GSCs via the RelB/P50 and p-STAT3 pathways. The induction of PMT by sEVs containing miR-27a-3p, miR-22-3p and miR-221-3p in a xenograft nude mouse model exacerbated radiotherapy resistance and thus decreased the benefits of radiotherapy. Collectively, these findings identified macrophage-derived sEVs (MDEs) as key regulators of PMT in GSCs and demonstrated that CHD7 is a novel inhibitor of PMT.