COL4A1 and cancer: Moreover, Lineage Program 5 exhibits downregulation of characteristic endothelial markers (e.g., PECAM1, VWF) and enrichment for mesenchymal markers (e.g., VIM, FN1, POSTN, COL4A1, COL4A2) (Figure 1F), suggestive of an endothelial-to-mesenchymal transition (EndMT) phenotype that is similar to epithelial–mesenchymal transition (EMT) and associated with abnormal pericyte recruitment, vasculogenesis, proliferation of radioresistant cancer cells with stem-like properties, and promotion of radiation-induced tissue fibrosis (16).