Figure 1.

Mechanisms of cytogenetic transformation of NECs to TECs. Proposed mechanisms: (a) Trans-differentiation: TECs arise from tumor cells, cancer stem cells or vascular progenitor cells. (b) Gene uptake: NECs can accept oncogenes by phagocytosis of apoptotic bodies or exosomes, released by tumor cells or endothelial progenitor cells. (c) Cell fusion: VPC or tumor cells can fuse with normal endothelial cells. (d) Tumor microenvironment: hypoxia, reactive oxygen species (ROS), growth factors, or cytokines in the tumor microenvironment may be another factor causing genetic instability. CSC—cancer stem cell; MVB—multivesicular body; NEC—normal endothelial cell; TEC—tumor endothelial cell; VPC—vascular progenitor cell.