FLT1 and astrocytoma (excluding glioblastoma): VEGF is a primary regulator, and its expression increases with tumor grade, promoting vascular proliferation and tumor progression.198 VEGFR-1 and VEGFR-2 activation play distinct roles in GBM initiation and malignancy.199 The overexpression of VEGF and VEGFR-1 in low-grade astrocytomas is correlated with poor prognosis, indicating their potential as prognostic biomarkers.200 Angiogenic factors in GBM are regulated by oncogene activation, tumor suppressor loss, and hypoxia.