Low- and high-grade glioma-associated vascular cells differentially regulate tumor growth [project1]
Glioma vascular cells (GVC) from high-grade IV gliomas (HG) are molecularly and functionally distinct from normal brain EC, and secrete higher levels of pro-tumorigenic factors that promote glioma growth and progression. However, it remains unclear whether GVC  from Low- Grade II/II gliomas (LG) also express pro-tumorigenic factors, and to what extent they functionally contribute to glioma growth. Here, we profile the transcriptomes of GVC from IDH-mutant (mIDH) LG and IDH-wildtype (wIDH) HG and show that they exhibit significant molecular and functional heterogeneity. LG-GVC show enrichment of extracellular matrix and cell cycle-related gene sets and sensitivity to anti-angiogenic drugs, whereas HG-GVC display an increase in immune response-related gene sets and anti-angiogenic resistance. Strikingly, conditioned media from LG-GVC inhibits the growth of wIDH glioblastoma cells, whereas HG-GVC promotes growth. In vivo co-transplantation of LG-GVC with tumor cells reduces growth, whereas HG-GVC enhances tumor growth in orthotopic xenografts. We identify ASPORIN (ASPN), a small leucine-rich repeat proteoglycan, enriched in LG-GVC as a growth suppressor of wIDH glioblastoma cells in vitro and in vivo. Together, these findings indicate that GVC from LG and HG gliomas are heterogeneous and differentially regulate tumor growth. Overall design: To determine the molecular identity of GVC isolated from primary GBM tumors by CD31-MACS sorting. CD31-positive GVC and CD31-negativeGBM tumor cell fractions were isolated and cultured for RNA extraction. Differential gene expression analysis was performed to characterize the enrichment of endothelial markers in GVC fractions. We also performed transcriptmic profiling of GVC cultured at different passages, early (EP, P2) and late passage (LP, P7) to determine if they maintain their identity in culture over long-term