RT Journal Article
SR Electronic
T1 The Dysregulated Pharmacology of Clinically Relevant <em>ESR1</em> Mutants is Normalized by Ligand-activated WT Receptor
JF Molecular Cancer Therapeutics
JO Mol Cancer Ther
FD American Association for Cancer Research
SP 1395
OP 1405
DO 10.1158/1535-7163.MCT-19-1148
VO 19
IS 7
A1 Andreano, Kaitlyn J.
A1 Baker, Jennifer G.
A1 Park, Sunghee
A1 Safi, Rachid
A1 Artham, Sandeep
A1 Oesterreich, Steffi
A1 Jeselsohn, Rinath
A1 Brown, Myles
A1 Sammons, Sarah
A1 Wardell, Suzanne E.
A1 Chang, Ching-yi
A1 Norris, John D.
A1 McDonnell, Donald P.
YR 2020
UL http://mct.aacrjournals.org/content/19/7/1395.abstract
AB The estrogen receptor (ER/ESR1) is expressed in a majority of breast cancers and drugs that inhibit ER signaling are the cornerstone of breast cancer pharmacotherapy. Currently, aromatase inhibitors are the frontline endocrine interventions of choice although their durability in metastatic disease is limited by activating point mutations within the ligand-binding domain of ESR1 that permit ligand-independent activation of the receptor. It has been suggested that the most commonly occurring ESR1 mutations would likely compromise the clinical activity of selective estrogen receptor downregulators and selective estrogen receptor modulators (SERMs) when used as second-line therapies. It was unclear, however, how these mutations, which are likely coexpressed in cells with ERWT, may impact response to ER ligands in a clinically meaningful manner. To address this issue, we dissected the molecular mechanism(s) underlying ESR1-mutant pharmacology in models relevant to metastatic disease. These studies revealed that the response of ESR1 mutations to ligands was dictated primarily by the relative coexpression of ERWT in cells. Specifically, dysregulated pharmacology was only evident in cells in which the mutants were overexpressed relative to ligand-activated ERWT; a finding that highlights the role of allelism in determining ER-mutant pharmacology. Importantly, we demonstrated that the antagonist activity of the SERM, lasofoxifene, was not impacted by mutant status; a finding that has led to its clinical evaluation as a treatment for patients with advanced ER-positive breast cancer whose tumors harbor ESR1 mutations.This article is featured in Highlights of This Issue, p. 1383