We have performed immunohistochemical studies of mortalin in normal an
d tumor human brain sections, In normal brain sections, the expression
was seen mainly as being confined to neurons. Normal astrocytes showe
d undetectable expression of this unique member of the heat shock 70 p
rotein family. Three grades of astrocyte tumors (low-grade astrocytoma
, anaplastic astrocytoma, and glioblastoma), however, showed an increa
sing number of mortalin-positive cells. Other types of brain tumors, s
uch as meningiomas, neurinomas, pituitary adenomas, and metastases, al
so showed elevated levels of mortalin expression compared to those in
the normal brain. Mortalin has earlier been reported to have different
ial intracellular distribution in normal and transformed cells in vitr
o. Therefore, we substantiated the present study with immunofluorescen
ce localization of the protein in normal and glioblastoma cells. The o
bservations indicated that the tumors might be expressing a nonpancyto
solic mortalin. An increase in number of mortalin-positive cells with
malignant progression of brain tumors and its correlation with Ki-67 (
a cell proliferation marker)positive cells further suggested an involv
ement of nonpancytosolic mortalin(s) in malignant transformation of ce
lls in vivo. (C) 1997 Academic Press.