Targeting the Tumor Micro-environmental in Glioblastoma: Barriers, Pathways, and Experimental Strategies

Glioblastoma (GBM) is the most common and aggressive malignant brain tumor in adults, with a median survival of 14-16 months per the Stupp regimen, a treatment which uses surgery followed by radiation and chemotherapy with temozolomide. Its resistance to treatment is largely due to the tumor microenvironment (TME), a complex network of immune cells; stromal components; and signaling pathways that promote tumor growth and suppress immune responses. In addition, the blood-brain barrier (BBB) restricts drug delivery and complicates immunotherapy strategies. This review examines the challenges and emerging directions in targeting the TME in glioblastoma. Sections include strategies for transiently and safely opening the BBB, the role of insulin-like growth factor (IGF) signaling in therapy resistance, immunosuppressive mechanisms within the TME, and the limited effectiveness of immune checkpoint blockade. We also review genetic mutations, innovative therapeutic agents, and survival-linked biomarkers. Across studies, we find that BBB disruption alters key endothelial genes, IGF signaling drives therapy resistance, the TME suppresses antitumor immunity, checkpoint inhibitors show limited benefit except in select immune-activated cases, and specific mutations such as IDH1 strongly predict patient survival. Collectively, this review highlights how understanding and targeting the TME may improve outcomes for patients with GBM and reveals how new technologies like focused ultrasound and single-cell transcriptomics are advancing the field.