This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Bergenheim, A. T. Articles by Henriksson, R. Search for Related Content PubMed PubMed Citation Articles by Bergenheim, A. T. Articles by Henriksson, R.

Estramustine-Binding Protein and Specific Binding of the Anti-Mitotic Compound Estramustine in Astrocytoma¹

Departments of Oncology [A. T. B., E. v. S., R. H.] and Neurosurgery [A. T. B.], Umeå University Hospital, S-901 85, Umeå; Department of Immunology, Pharmacia Oncology Immunology, S-223 63 Lund [P. B. H., S.]; and Department of Oncology, Akademiska Sjukhuset, S-751 85 Uppsala [J. B.], Sweden

Estramustine-binding protein (EMBP) is a M_r 46,000 heterodimeric protein originally isolated from prostatic tissue. It has a demonstrated high affinity for, and selective binding of, estramustine, which is a derivative of 17ß-estradiol and nornitrogen mustard with antimitotic activity. In this study, we have analysed the expression of an EMBP-like protein in astrocytoma specimens. Immunohistochemistry revealed a pronounced reactivity for EMBP in astrocytoma grades III–IV as well as in metastatic prostatic adenocarcinoma used as positive control. In astrocytoma grades I–II, the expression was weak. The EMBP-like protein was quantified by radioimmunoassay in astrocytoma tumor tissue with higher concentrations in malignant astrocytoma, grades III–IV, compared to grades I–II tumors. Western immunoblotting of immunoaffinity purified EMBP-like protein under nonreducing conditions revealed an immunoreactivity corresponding to M_r 138,000 and 200,000, indicating a different structure of EMBP in astrocytoma compared to prostatic tissue. Specific binding and the presence of saturable binding sites for ³H-labeled estramustine were demonstrated in astrocytoma tissues expressing EMBP-like protein. Scatchard plot analysis showed a K_d at 30 nM, which suggests a binding affinity for estramustine in the same range as previously reported for EMBP in the prostate, Moreover, the number of estramustine binding sites/g tumor as calculated from the Scatchard plots was well correlated with the EMBP levels determined in the radioimmunoassay. In conclusion, an EMBP-like protein is expressed in astrocytoma. This protein may be responsible for the specific binding of estramustine in the tumor tissue. Whether this specific binding of estramustine is of importance for the cytotoxic effect in glioma cells remains to be evaluated.

¹ This investigation was supported by grants from The Swedish Cancer Society and The Lion Cancer Foundation, Umeå; Swedish Society for Medical Research, Karolinska Institutet, Stockholm; Umeå University; and Lundbergs Foundation for Medical Research, Gothenburg, Sweden.

² To whom requests for reprints should be addressed.

Received 4/18/94. Accepted 7/20/94.