Exosome‐transmitted podoplanin promotes tumor‐associated macrophage‐mediated immune tolerance in glioblastoma

Aims Glioblastoma is the most frequent and aggressive primary brain tumor, characterized by rapid disease course and poor treatment responsiveness. The abundance of immunosuppressive macrophages in glioblastoma challenges the efficacy of novel immunotherapy. Methods Bulk RNA‐seq and single‐cell RNA‐seq of glioma patients from public databases were comprehensively analyzed to illustrate macrophage infiltration patterns and molecular characteristics of podoplanin (PDPN). Multiplexed fluorescence immunohistochemistry staining of PDPN, GFAP, CD68, and CD163 were performed in glioma tissue microarray. The impact of PDPN on macrophage immunosuppressive polarization was investigated using a co‐culture system. Bone marrow‐derived macrophages (BMDMs) and OT‐II T cells isolated from BALB/c and OT‐II mice respectively were co‐cultured to determine T‐cell adherence. Pathway alterations were probed through RNA sequencing and western blot analyses. Results Our findings demonstrated that PDPN is notably correlated with the expression of CD68 and CD163 in glioma tissues. Additionally, macrophages phagocytosing PDPN‐containing EVs (EVsPDPN) from GBM cells presented increased CD163 expression and augmented secretion of immunoregulatory cytokine (IL‐6, IL‐10, TNF‐α, and TGF‐β1). PDPN within EVs was also associated with enhanced phagocytic activity and reduced MHC II expression in macrophages, compromising CD4+ T‐cell activation. Conclusions This investigation underscores that EVsPDPN derived from glioblastoma cells contributes to M2 macrophage‐mediated immunosuppression and is a potential prognostic marker and therapeutic target in glioblastoma. The schematic diagram illustrates the mechanism of PDPN‐mediated macrophage immunosuppressive polarization. PDPN‐overexpressed GBM cells secrete PDPN‐containing EVs, followed by phagocytosis by unpolarized M0 macrophages, which induce immunosuppressive polarization of macrophages, manifested by the release of immunosuppressive cytokines, ERK phosphorylation activation, diminished MHC II expression, and incompetence to CD4+ T activation.