Estradiol increases cell growth in human astrocytoma cell lines through ERα activation and its interaction with SRC-1 and SRC-3 coactivators

Estradiol (E2) regulates several cellular functions through the interaction with estrogen receptor subtypes, ER alpha and ER beta, which present different functional and regulation properties. ER subtypes have been identified in human astrocytomas, the most common and aggressive primary brain tumors. We studied the role of ER subtypes in cell growth of two human astrocytoma cell lines derived from tumors of different evolution grades: U373 and D54 (grades III and IV, respectively). E2 significantly increased the number of cells in both lines and the co-administration with an ER antagonist (ICI 182, 780) significantly blocked E2 effects. ER alpha was the predominant subtype in both cell lines. E2 and ICI 182, 780 down-regulated ER alpha expression. The number of U373 and D54 cells significantly increased after PPT (ER alpha agonist) treatment but not after DPN (ER beta agonist) one. To determine the role of SRC-1 and SRC-3 coactivators in ER alpha induced cell growth, we silenced them with RNA interference. Coactivator silencing blocked the increase in cell number induced by PPT. The content of proteins involved in proliferation and metastasis was also determined after PPT treatment. Western blot analysis showed that in U373 cells the content of PR isoforms (PR-A and PR-B), EGFR, VEGF and cyclin D1 increased after PPT treatment while in D54 cells only the content of EGFR was increased. Our results demonstrate that E2 induces cell growth of human astrocytoma cell lines through ER alpha and its interaction with SRC-1 and SRC-3 and also suggest differential roles of ER alpha on cell growth depending on astrocytoma grade. (C) 2011 Elsevier B.V. All rights reserved.