AQP4 and brain neoplasm: Previous evidence reveals a significantly positive relationship of AQP4 upregulation with increased expression of VEGF and HIF-1α proteins, which are involved in neovascularization (Mou et al. 2010; Yang et al. 2012), contrary to occludin expression, a tight junction protein, which is downregulated in brain tumors and meningiomas with PTBE (Park et al. 2006).