COL4A1 and neoplasm: Cluster 6 ECs may be involved in mediating tumor vascular growth and basement membrane (BM) remodeling, as evidenced by the upregulation of BM remodeling genes (COL4A1, COL4A2, LAMB1, LAMC1, LAMA4, HSPG2, PXDN, PLOD1, and MMP2), angiogenesis-related genes (PGF, APLN, and SPARC), and cytoskeletal genes (TMSB4X, ACTB, ACTG1, TMSB10, CFLS, and VIM) in cluster 6 ECs (Figures 6C, D).