Prognostic implication of estramustine-binding protein in astrocytoma

Estramustine-binding protein (EMBP) is a glycoprotein shown to be expressed in the cytoplasm of astrocytoma cells. Originally, it was found in rat prostatic tissue and described as a secretory protein. Its expression has been demonstrated to positively correlate with the degree of neoplastic transformation in astrocytoma tissue. EMBP has been proposed to be responsible for a specific and high affinity binding of estramustine in astrocytoma tumor tissue. In this study the expression of EMBP was evaluated by immunohistochemistry and radioimmunoassay in a series of astrocytoma of different grades. Staining intensity and the number of stained cells increased with the degree of malignancy. The levels of EMBP were 1.3-6.2 ng/g tumor tissue with higher levels in tumors of grade III to IV compared to grade I and II. It was found that a high expression of EMBP always implied a short survival of the patients. On the other hand, a low expression of EMBP did not always assure a favorable prognosis. It is proposed that EMBP might have a value to predict survival in patients with astrocytoma, especially if estramustine is to be included in the treatment schedule. However, further extended studies are needed before final conclusions can be made.