(A) Representative micrographs of BT12 xenografts immunostained with anti–collagen IV (green) and anti-podocalyxin (red). Nuclei were counterstained with DAPI (blue). Scale bar: 40 μm. Arrows indicate empty basement membrane sleeves devoid of endothelium. (B) Quantification of collagen IV⁺/PODXL^– empty sleeves in control and CD109-silenced BT12 xenografts (n = 10). (C) Representative micrographs of BT12 xenografts immunostained with anti-human vimentin (green) and anti-mouse CD31 (red). Nuclei were counterstained with DAPI (blue). Scale bars: 2 mm or 40 μm as indicated. Quantification of the average tumor blood vessel size (D) and density (E) in control and CD109-silenced BT12 xenografts (n = 10). (F) Quantification of the secreted ANG1 and ANG2 levels from the cell culture supernatants of CD109-silenced and nontargeted control BT12 GSCs (n = 2). (G) Expression of ANGPT1 and ANGPT2 mRNA levels determined by total RNA-Seq in CD109-silenced and nontargeted BT12 GSCs at the indicated time points. (H) Representative micrographs of BT12 xenografts immunostained with anti-human NUMA (green) and anti-NG2 (red). Nuclei were counterstained with DAPI (blue). Scale bars: 2 mm or 40 μm as indicated. (I) Representative micrographs of BT12 xenografts immunostained with anti–α-SMA (green) and anti-CD31 (red). Nuclei were counterstained with DAPI (blue). Scale bar: 40 μm. (J) Quantification of the α-SMA⁺ tumor pericytes in control and CD109-silenced BT12 xenografts (n = 10). (K) Representative micrographs of BT12 xenografts immunostained with anti-NG2 (green) and anti-CD31 (red). Nuclei were counterstained with DAPI (blue). Scale bar: 40 μm. (L) Quantification of the pericyte coverage in control and CD109-silenced BT12 xenografts (n = 10). P values were calculated by using the unpaired 2-tailed t test except for F and G, where a t test with Mann-Whitney post hoc test was used.