TET2-driven demethylation of ANG promotes angiogenesis and malignant transformation in oligodendroglioma.

Oligodendrogliomas (OG) are indolent yet inevitably progressive gliomas in which angiogenesis is tightly linked to malignant transformation, but the underlying epigenetic mechanisms remain unclear. By integrating public datasets of primary and malignant transformed OG specimens, patient-derived cell lines and orthotopic xenograft models, we identify angiogenin (ANG) as a key pro-angiogenic regulator whose high expression correlates with increased microvessel density, enhanced proliferation and poor overall survival. Promoter methylation analyses reveal that ANG is heavily methylated in low-grade tumors and that hypomethylation of three CpG-rich regions including the prognostic site e.g., cg10850001, associates with increased ANG expression, higher tumor grade and worse outcome. Functional studies show that ANG knockdown suppresses VEGFA and Ki67 expression, reduces endothelial tube formation and intratumoral microvessel density, and significantly prolongs survival in Oligodendroglioma PDOX mice, whereas pharmacologic demethylation with decitabine decreases methylation at the ANG CpG hotspot (CpG islands 5 and 6-7), upregulates ANG and accelerates malignant phenotypes. Among TET dioxygenases, TET2 is selectively upregulated in malignant oligodendroglioma, directly binds to the ANG upstream regulatory region, with enrichment at the ANG CpG hotspot, and enhances its activity; TET2 depletion increases methylation at the ANG CpG hotspot, downregulates ANG and pro-angiogenic markers, and impairs angiogenesis, effects that are rescued by ANG re-expression. The cell-permeable itaconate derivative 4-octyl itaconate (OI), an itaconate derivative reported to inhibit TET activity, restores methylation at the ANG CpG hotspot, suppresses TET2-ANG signaling and cooperates with Temozolomide (TMZ) to inhibit tumor growth and extend survival in PDOX models. These findings define a TET2-ANG-angiogenesis axis that promotes an angiogenic program associated with malignant progression in oligodendroglioma and support itaconate-based pharmacologic TET modulation as a promising but still preclinical potential therapeutic strategy. Schematic diagram. Proposed TET2-ANG axis in oligodendroglioma progression. Solid arrows indicate relationships directly supported by experimental evidence in this study, including TET2-dependent demethylation of the ANG promoter, increased ANG expression, and downstream changes in VEGFA expression, angiogenesis, and malignant progression. These downstream effects are also supported by our previous study6. Dashed arrows indicate proposed or indirectly supported steps that were not directly tested for causality here (e.g., VEGFA secretion/transfer to the extracellular space, VEGFA-mediated activation of endothelial cells, and the contribution of angiogenesis to malignant progression). The inhibitory bar denotes pharmacologic inhibition; a dashed inhibitory bar indicates putative target engagement inferred from downstream readouts.