CDH5 and neoplasm: Tumor ECs (TECs) are poorly interconnected due to lower levels of the junctional molecule VE-Cadherin, have lost polarity, are poorly covered with pericytes and often leave gaps which reduces barrier function and allows tumor cells to escape and metastasize to distant organs (Jain, 2005; Carmeliet and Jain, 2011; Cantelmo et al., 2016) (Figure 4A).