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Diffuse Midline Glioma (DMG), often formerly called Diffuse Intrinsic Pontine Glioma (DIPG) when in the brainstem, DMG/DIPG is a lethal pediatric brain tumor defined by infiltrative growth, resistance to conventional therapies, and a profound immunosuppressive tumor microenvironment (TME). Tumor-associated macrophages (TAMs), including resident microglia and infiltrating monocyte-derived macrophages, are the predominant immune population in DMG/DIPG. These cells adopt an immunosuppressive, pro-tumor state, promoting immune evasion and limiting the efficacy of therapies such as chimeric antigen receptor (CAR) T cells. Reprogramming TAMs toward a pro-inflammatory, anti-tumor phenotype offers a promising strategy to remodel the DMG/DIPG microenvironment. This review is the first to provide a comprehensive, integrative perspective on TAM-directed strategies in DMG/DIPG, spanning molecular, epigenetic, and biophysical approaches. We summarize TAM-mediated tumor progression and therapy resistance, and discuss molecular reprogramming strategies, including colony-stimulating factor 1 receptor (CSF1R) inhibition, microRNA-based circuits, and epigenetic modulators such as histone deacetylase (HDAC) and bromodomain and extra-terminal domain (BET) inhibitors. Nanoparticle-mediated delivery systems allow selective TAM targeting and enhanced blood-brain barrier (BBB) penetration. Additional strategies, including oncolytic viruses and macrophage-specific checkpoint blockade (e.g., CD47/SIRPα axis inhibitors), simultaneously promote tumor clearance and immune activation. We also highlight emerging biophysical approaches to modulate TAM function in situ . Photodynamic therapy (PDT) induces immunogenic cell death and pro-inflammatory macrophage activity, while focused ultrasound (FUS) transiently disrupts the BBB to enhance drug delivery and immune infiltration. Photobiomodulation and low-level light therapy (LLLT) may influence macrophage metabolism and phenotype, though their application in DMG/DIPG remains largely unexplored. Finally, we discuss combinatorial strategies integrating TAM reprogramming with CAR T cell therapy or chemotherapy to overcome the immunologically “cold” nature of DMG/DIPG. By uniting mechanistic insights with translational opportunities, this review establishes TAM reprogramming as a critical, underexplored frontier in DMG/DIPG immunotherapy, offering the potential to render an otherwise intractable tumor immunologically targetable.
Khorsandi et al. (Tue,) studied this question.