Expression of estramustine-binding protein in ependymomas and in human and developing rat ependymal cells

Summary The mainstays of primary treatment of ependymoma are aggressive surgery followed by radiotherapy. Although spreading occasionally occurs in the cerebrospinal pathways, chemotherapy is still not established and no ultimate drug has so far been found. Estramustine-phosphate (EMP), with a demonstrated effect on astrocytomain vitro, has been shown to penetrate the blood-tumor barrier and to accumulate in human brain tumor tissue including ependymoma. It has been proposed that the cytotoxic effect of EMP depends on the presence of a binding protein, estramustine-binding protein (EMBP). In the present paper we have, for the first time, immunohistochemically demonstrated an EMBP-like protein in a series of ependymomas. Immunoreactivity was found within the cytoplasm of the tumor cells with a tendency to increase with increasing malignancy of the tumor. In addition, the occurence of EMBP-like protein was demonstrated in human ependymal cells. In the rat brain, a weak immunoreactivity was detected in early fetal neuroepithelial cells while the staining intensity was increased in mature ependymal cells in late fetal, neonatal, and adult rat. Thus, immunoreactivity for an EMBP-like protein was demonstrated in ependymoma tissue, normal human ependyma and in the developing rat ependymal cells.