TRIM25 promotes glioblastoma progression by stabilizing HIF-1α expression in normoxia through K11/K29 polyubiquitination

Glioblastoma (GBM) frequently activates hypoxia signaling even under normoxic conditions, yet the mechanism sustaining hypoxia-inducible factor-1α (HIF-1α) stability remains unclear. Here, we identify the E3 ubiquitin ligase TRIM25 as a key driver of this phenomenon. TRIM25, aberrantly upregulated in GBM, directly binds HIF-1α and catalyzes K11/K29-linked polyubiquitination at lysine 532 of hydroxylated HIF-1α, preventing its canonical proteasomal degradation. This non-canonical ubiquitin modification stabilizes HIF-1α despite normal oxygen availability and sustains a pseudohypoxic transcriptional program in GBM cells. Functional studies in GBM cell lines, patient-derived cultures, and tumor models demonstrate that TRIM25-mediated HIF-1α stabilization promotes tumor proliferation, invasion, and angiogenic potential. Importantly, small-molecule screening identified T7117 as an inhibitor that disrupts the TRIM25-HIF-1α interaction, suppresses tumor growth, and enhances temozolomide efficacy. Together, our findings uncover a previously unrecognized ubiquitin mechanism that stabilizes hydroxylated HIF-1α under normoxia, revealing the TRIM25-HIF-1α axis as a driver of GBM pseudohypoxia and a potential therapeutic target.