TMIC-28. Glioblastoma-derived ribosomal protein S19 exacerbates cerebral edema through C5AR1 in tumor-associated macrophages

Abstract BACKGROUND Cerebral edema in glioblastoma (GBM) leads to increased intracranial pressure, neurological dysfunctions, and fatal brain herniation. Our previous single-cell transcriptomic analysis of GBM patient samples identified a specific tumor-to-tumor-associated macrophage (TAM) interaction between tumor-derived ribosomal protein S19 (RPS19) and the C5AR1 in inflammatory TAMs in peritumoral regions. Given the critical role of inflammation in edema formation, this study investigated the underlying mechanisms in TAMs, elucidating how the RPS19-C5AR1 axis contributed to GBM-induced edema and protumoral feedback interactions. METHODS Extracellular RPS19 and downstream C5AR1 signaling molecules were analyzed by Western blotting, while mRNA levels were measured by qRT-PCR. Lentiviral shRNA targeting C5AR1 and the transcription factor PU.1/SPI1 was used in macrophage-like cells. A multicellular co-culture system modeled intercellular interactions. Recombinant proteins of RPS19 or C5a were utilized. A pharmacological inhibitor targeting C5AR1 and its downstream signaling, PMX-53, was tested in vitro and in an orthotopic GBM mouse model. Peritumoral edema and related markers were assessed by H&E and immunohistochemistry staining. RESULTS Under proliferative stress, hypoxia, chemotherapy, or oxidative stress, GBM cells released RPS19 into the extracellular space. In polarized M1 macrophage-like cells, RPS19 promoted proliferation and upregulated CD68, C5AR1, and IL-1β, effects not observed with C5a as an alternative. By pharmacologic and genetic inhibition, RPS19 transduced signaling through the C5AR1-Akt-PU.1/SPI1 axis. In vivo, disrupting RPS19-C5AR1 signaling by PMX-53 reduced peritumoral edema and the expression of AQP4. Beyond vasogenic mechanisms, RPS19-C5AR1 axis triggered astrocyte swelling and reactivation via macrophage-derived IL-1β. IL-1β further induced astrocytic CCL2, TGF-β1, and IL-6, fostering a protumoral microenvironment. CONCLUSIONS The RPS19-C5AR1 axis drives GBM-associated cerebral edema by promoting IL-1β-mediated astrocyte reprogramming and inflammatory signaling. Targeting this pathway with agents such as PMX-53 may mitigate edema and its protumoral consequences in GBM.