ENDOTHELIAL-CELL MARKER PAL-E REACTIVITY IN BRAIN-TUMOR, DEVELOPING BRAIN, AND BRAIN DISEASE

Background. The endothelial cell marker PAL-E is not reactive to vesse ls in the normal brain. The present study concerns the PAL-E reactivit y in brain tumors in contrast to normal brain and nonneoplastic brain disease. Methods. A total of 122 specimens were examined: brain tumors (n = 94), nonneoplastic brain disease (n = 19), normal brain (n = 8), and fetal brain (n = 1). Standard immunohistochemical procedures usin g a panel of endothelial cell markers were applied to detect vessels r eactive to PAL-E. Results. PAL-E reactivity to endothelial cells was f ound in all cases of glioblastoma multiforme, in 75% of the cases of a naplastic astrocytoma, and in 46% of the cases of astrocytoma. Further more, PAL-E reactivity was present in diseases with a developmental et iology, such as primitive tumors and congenital vascular malformations . The developing human brain (6-weeks' gestation age) and special site s of the mature brain, sites without blood-brain barrier, showed a str ong reactivity, which indicates a relation with the status of blood-br ain barrier development. Conclusions. PAL-E is the only marker out of a panel of endothelial cell markers that shows no reactivity to endoth elial cells in the normal brain with an intact blood-brain barrier. In primary and metastatic brain tumors, PAL-E is reactive to endothelial cells, except for 25% of anaplastic astrocytoma and 54% of astrocytom a. PAL-E reactivity in brain tumors most likely is related to angiogen esis and to blood-tumor barrier properties not present in the normal b lood-brain barrier.