Bone Tumor Microenvironment Is Associated with Meningioma Enlargement and Inflammatory Transcriptional States: A Candidate Role for Macrophage-Derived IL-1β.

Background/Objectives: Meningiomas frequently involve the adjacent skull bone. The bone tumor microenvironment (TME) represents a unique niche in bone-invasive tumors and bone metastases, and can promote tumor progression through tumor-stromal interactions. We hypothesized that the bone TME may contribute to tumor cell transcriptional changes and tumor growth in meningioma. Methods: Human malignant meningioma cell lines, IOMM-Lee and HKBMM, were implanted over the calvarial bone (bone TME) and into the dorsal skin (non-bone TME) of BALB/c-nu/nu mice. Tumors from the IOMM-Lee model underwent bulk RNA sequencing with computational separation of human- and mouse-derived reads, enabling ligand-target interaction analysis of stromal cell-to-tumor cell signaling. Differential gene expression analysis, enrichment analysis, ligand-target interaction analysis, multiplex immunofluorescence, and immunohistochemistry were performed. Results: Tumor volume was significantly greater in the bone TME than in the non-bone TME in both models, whereas the Ki-67 labeling index was significantly reduced. Transcriptomic analysis revealed distinct tumor cell transcriptional states in the bone TME, characterized by upregulation of inflammation-related genes and enrichment of inflammatory signaling pathways, including interferon responses and NF-κB signaling. Ligand-target interaction analysis of stromal cell-to-tumor cell signaling identified stromal IL1B as a candidate regulator of inflammatory transcriptional programs in tumor cells. F4/80-positive macrophages expressed IL-1β, and tumor cells were positive for phospho-IKKα/β and phospho-IκBα in the bone TME. Conclusions: Tumor-stromal interactions potentially involving macrophage-derived IL-1β may be associated with inflammatory transcriptional programs in meningioma cells and with meningioma enlargement in the bone TME. These interactions may be therapeutically relevant in meningioma with bone involvement.