ERβ alters the chemosensitivity of luminal breast cancer cells by regulating p53 function

// Igor Bado 1 , Eric Pham 2 , Benjamin Soibam 3 , Fotis Nikolos 1 , Jan-Åke Gustafsson 1, 4 and Christoforos Thomas 1 1 Department of Biology and Biochemistry, Center for Nuclear Receptors and Cell Signaling, University of Houston, Houston, Texas, USA 2 Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA 3 Department of Computer Science and Engineering Technology, University of Houston-Downtown, Huston, Texas, USA 4 Center for Innovative Medicine, Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden Correspondence to: Christoforos Thomas, email: thomaschristoforos@gmail.com Keywords: estrogen receptor β; p53; breast cancer; DNA damage response; therapy response Received: September 27, 2017      Accepted: March 21, 2018      Published: April 27, 2018 ABSTRACT Estrogen receptor α (ERα)-positive breast cancers tend to develop resistance to both endocrine therapy and chemotherapy. Despite recent progress in defining molecular pathways that confer endocrine resistance, the mechanisms that regulate chemotherapy response in luminal tumors remain largely elusive. Luminal tumors often express wild-type p53 that is a major determinant of the cellular DNA damage response. Similar to p53, the second ER subtype, ERβ, has been reported to inhibit breast tumorigenesis by acting alone or in collaboration with p53. However, a synergistic mechanism of action has not been described. Here, we suggest that ERβ relies on p53 to elicit its tumor repressive actions in ERα-positive breast cancer cells. Upregulation of ERβ and treatment with ERβ agonists potentiates the tumor suppressor function of p53 resulting in decreased survival. This effect requires molecular interaction between the two proteins that disrupts the inhibitory action of ERα on p53 leading to increased transcriptional activity of p53. In addition, we show that the same interaction alters the chemosensitivity of endocrine-resistant cells including their response to tamoxifen therapy. Our results suggest a collaboration of ERβ and p53 tumor suppressor activity in breast cancer cells that indicates the importance of ligand-regulated ERβ as a tool to target p53 activity and improve the clinical management of resistant disease.