COL4A1 and neoplasm: We found that tumor endothelial cells from brain metastases were highly expressed in angiogenesis-related genes such as COL4A1, COL4A2, HSPG2, COL15A1, and SPARC (Fig. 5E), and GSVA results also showed that tumor endothelial cells from brain metastases were enriched in angiogenesis (Fig. 5F), these results suggest that endothelial cells in brain metastases have a higher angiogenic capacity than primary tumor tissues.