TY - JOUR
T1 - Resistance to antiestrogen arzoxifene is mediated by overexpression of cyclin D1
AU - Zwart, Wilbert
AU - Rondaij, Mariska
AU - Jalink, Kees
AU - Sharp, Z. Dave
AU - Mancini, Michael A.
AU - Neefjes, Jacques
AU - Michalides, Rob
N1 - Copyright:
Copyright 2009 Elsevier B.V., All rights reserved.
PY - 2009/9
Y1 - 2009/9
N2 - Resistance to tamoxifen treatment occurs in approximately 50% of the estrogen receptor (ER)α-positive breast cancer patients. Resistant patients would benefit from treatment with other available antiestrogens. Arzoxifene is an effective growth inhibitor of ERα-positive breast cancer cells, including tamoxifen-resistant tumors. In this study, we show that overexpression of a regular component of the ERα transcription factor complex, cyclin D1, which occurs in approximately 40% of breast cancer patients, renders cells resistant to the new promising antiestrogen, arzoxifene. Overexpression of cyclin D1 alters the conformation of ERα in the presence of arzoxifene. In this altered conformation, ERα still recruits RNA polymerase II to an estrogen response element-containing promoter, inducing transcription of an ERα-dependent reporter gene and of endogenous pS2, and promoting arzoxifene-stimulated growth of MCF-7 cells. Arzoxifene is then converted from an ERα antagonist into an agonist. This can be explained by a stabilization of the ERα/steroid receptor coactivator-1 complex in the presence of arzoxifene, only when cyclin D1 is overexpressed. These results indicate that subtle changes in the conformation of ERα upon binding to antiestrogen are at the basis of resistance to antiestrogens.
AB - Resistance to tamoxifen treatment occurs in approximately 50% of the estrogen receptor (ER)α-positive breast cancer patients. Resistant patients would benefit from treatment with other available antiestrogens. Arzoxifene is an effective growth inhibitor of ERα-positive breast cancer cells, including tamoxifen-resistant tumors. In this study, we show that overexpression of a regular component of the ERα transcription factor complex, cyclin D1, which occurs in approximately 40% of breast cancer patients, renders cells resistant to the new promising antiestrogen, arzoxifene. Overexpression of cyclin D1 alters the conformation of ERα in the presence of arzoxifene. In this altered conformation, ERα still recruits RNA polymerase II to an estrogen response element-containing promoter, inducing transcription of an ERα-dependent reporter gene and of endogenous pS2, and promoting arzoxifene-stimulated growth of MCF-7 cells. Arzoxifene is then converted from an ERα antagonist into an agonist. This can be explained by a stabilization of the ERα/steroid receptor coactivator-1 complex in the presence of arzoxifene, only when cyclin D1 is overexpressed. These results indicate that subtle changes in the conformation of ERα upon binding to antiestrogen are at the basis of resistance to antiestrogens.
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U2 - 10.1210/me.2008-0268
DO - 10.1210/me.2008-0268
M3 - Article
C2 - 19477949
AN - SCOPUS:69449095853
VL - 23
SP - 1335
EP - 1345
JO - Molecular Endocrinology
JF - Molecular Endocrinology
SN - 0888-8809
IS - 9
ER -