ErbB3 downregulation enhances luminal breast tumor response to antiestrogens
Meghan M. Morrison, … , Suleiman Massarweh, Rebecca S. Cook
Meghan M. Morrison, … , Suleiman Massarweh, Rebecca S. Cook
Published September 3, 2013
Citation Information: J Clin Invest. 2013;123(10):4329-4343. https://doi.org/10.1172/JCI66764.
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Research Article Oncology

ErbB3 downregulation enhances luminal breast tumor response to antiestrogens

Abstract

Aberrant regulation of the erythroblastosis oncogene B (ErbB) family of receptor tyrosine kinases (RTKs) and their ligands is common in human cancers. ErbB3 is required in luminal mammary epithelial cells (MECs) for growth and survival. Since breast cancer phenotypes may reflect biological traits of the MECs from which they originate, we tested the hypothesis that ErbB3 drives luminal breast cancer growth. We found higher ERBB3 expression and more frequent ERBB3 gene copy gains in luminal A/B breast cancers compared with other breast cancer subtypes. In cell culture, ErbB3 increased growth of luminal breast cancer cells. Targeted depletion of ErbB3 with an anti-ErbB3 antibody decreased 3D colony growth, increased apoptosis, and decreased tumor growth in vivo. Treatment of clinical breast tumors with the antiendocrine drug fulvestrant resulted in increased ErbB3 expression and PI3K/mTOR signaling. Depletion of ErbB3 in fulvestrant-treated tumor cells reduced PI3K/mTOR signaling, thus decreasing tumor cell survival and tumor growth. Fulvestrant treatment increased phosphorylation of all ErbB family RTKs; however, phospho-RTK upregulation was not seen in tumors treated with both fulvestrant and anti-ErbB3. These data indicate that upregulation of ErbB3 in luminal breast cancer cells promotes growth, survival, and resistance to fulvestrant, thus suggesting ErbB3 as a target for breast cancer treatment.

Authors

Meghan M. Morrison, Katherine Hutchinson, Michelle M. Williams, Jamie C. Stanford, Justin M. Balko, Christian Young, Maria G. Kuba, Violeta Sánchez, Andrew J. Williams, Donna J. Hicks, Carlos L. Arteaga, Aleix Prat, Charles M. Perou, H. Shelton Earp, Suleiman Massarweh, Rebecca S. Cook

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Figure 3

Upregulation of ErbB3 signaling upon ER inhibition in luminal breast cancer cells.

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Upregulation of ErbB3 signaling upon ER inhibition in luminal breast can...
(A and B) Immunofluorescence (A) and flow cytometry (B) of ErbB3 in cells cultured for 24 hours with or without fulvestrant. Original magnification, ×200. (B) Left panel shows the ErbB3hi percentage of cells (n = 50,000). Right panel shows average fluorescent intensity per cell. (C–E) Western blot analysis of cell lysates harvested after 0–72 hours of 1 μM fulvestrant. (F) Cells transfected with ErbB3-siRNA or control-siRNA were treated 24 hours with fulvestrant or DMSO prior to Western blot analysis for ErbB3 and ERα. (G) Real-time qPCR analysis of ERBB3 in cells treated 0–24 hours with fulvestrant (1 μM). Average relative ErbB3 levels shown ± SD. *P < 0.05, 1-way ANOVA. (H) Increased mRNA encoding ErbB receptors and ligands ± SD in fulvestrant-treated MCF7 cells measured in publicly available expression data (GSE14986). (I) MCF7 cells transfected with a human ERBB3 gene promoter (–1000/+1) luciferase reporter plasmid were treated with increasing fulvestrant doses for 24 hours. Average (n = 3) RLUs per μg protein ± SD are shown. One-way ANOVA. (J) Real-time qPCR analysis of ERBB3 mRNA in MCF7 cells treated 24 hours ± fulvestrant and actinomycin D (ActD). Average fold change is shown ± SD. ***P < 0.001. (K) Western blot analysis of fulvestrant-treated MCF7 lysates. Cycloheximide (CHX) was added for the final 0–4 hours.