Estrogen receptor beta (ERbeta) protein expression correlates with BAG-1 and prognosis in brain glial tumours

Estrogen receptor beta (ERbeta) is an important mediator of estrogen function in a variety of tissues. Its expression declines in breast, ovarian, prostatic and colon carcinomas as well as in astrocytic tumours. BAG-1 is a multifunctional protein with an important role in neoplasia and is possibly regulated by estrogen receptors. One of the direct targets of BAG-1 is HSP70. The purpose of this study was to analyse the expression pattern of these proteins in two distinct types of glial neoplasms, to investigate their possible correlation and probe their impact on prognosis. ERbeta, BAG-1 and HSP70 protein expression was monitored immunohistochemically in 66 cases of astrocytomas and 20 oligodendrogliomas. In astrocytic tumours low ERbeta expression correlated significantly with high grade (P < 0.001), higher expression of cytoplasmic BAG-1 (P < 0.001) and worse survival (log rank P = 0.02). Multivariate analysis revealed that ERbeta expression had a prognostic value for overall survival in these patients (Cox P = 0.03), which was not dependent on grade. There was also statistically significant association of BAG-1 nuclear expression with HSP70 cytoplasmic expression. Our results strengthen the hypothesis that ERbeta, BAG-1 and HSP70 play an important role in the pathogenesis and progression of glial neoplasms. Moreover, ERbeta expression in astrocytic tumors might be an important prognostic factor for survival.