ELEVATED LEVELS OF MORTALIN EXPRESSION IN HUMAN BRAIN-TUMORS

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.