The BTB is characterized by reduction in the expression of tight junctions, induced by vascular endothelial growth factor (VEGF) secretion from tumor cells, heterogeneous pericyte coverage with increased desmin and reduced PDGFR-β expression on the cell surface, increased number of reactive astrocytes with shrinkage of astrocyte endfeet and breakdown of basal membrane [26,27]. The gene discussed is VEGFA; the disease is neoplasm.