Tumor-associated astrocytes augment cholesterol synthesis to support glioblastoma growth through alternatively spliced Quaking (QKI) isoforms

Background Glioblastoma (GBM) is a highly aggressive brain tumor with limited treatment options. Tumor-associated astrocytes (TAAs) are crucial components of the GBM microenvironment, yet the contribution of alternative splicing (AS) in TAAs to tumor progression remains unclear. Methods Transcriptomic and molecular analyses of GBM-associated astrocytes revealed a GBM-induced isoform switch in the RNA-binding protein Quaking (QKI) from the QKI-6 isoform to QKI-5 isoform. The biological role of QKI-5 was examined through gain- and loss-of-function approaches in human astrocytes and co-culture systems with patient-derived glioma stem-like cells (GSCs). In vitro proliferation and sphere-formation assays, along with in vivo orthotopic xenograft models, were used to evaluate tumor growth. Immunoprecipitation and AlphaFold3 structural prediction were performed to investigate the mechanistic interaction between QKI-5 and sterol regulatory element-binding protein 2 (SREBP2). Results GBM-induced QKI-5 interacts with SREBP2 to transcriptionally activate cholesterol metabolic enzymes, enhancing astrocyte-derived cholesterol production and promoting GBM growth. Knockdown of QKI-5 or inhibitors for SREBP2-driven signaling suppressed astrocyte-mediated tumor-supportive effects in vitro and in vivo. Conclusion QKI-5 drives astrocytic metabolic reprogramming via the QKI-5–SREBP2 axis, fostering a cholesterol-rich tumor microenvironment that supports GBM progression. Targeting this pathway offers a potential therapeutic strategy.