How Does the PAL-E Finding Relate to the Literature?
Leenstra and coworkers [30] found PAL-E reactivity of endothelial cells in brain tumors, in diseases with a developmental etiology such as primitive tumors and congenital vascular malformations, and in the developing human brain. They suggest that PAL-E expression relates to the specialized endothelial cell function as part of the blood-brain barrier. Leenstra et al [30] also suggested that PAL-E expression relates to vascular neogenesis. We have looked into this option using EN- 4, a membrane marker for all endothelial cells, but could not find such a relation. Furthermore, we found no correlation between PAL-E reactivity and expression of adhesion molecules, endothelin, or endoglin. The membrane-associated endoglin molecule is a transforming growth factor- beta-binding protein that is expressed most abundantly on endothelial cells in tissues with inflammatory characteristics. Endoglin expression is also found in tumors and granulation tissue in which neovascularization can be found.
