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 6

Fulvestrant-mediated mTOR upregulation requires signaling through the ErbB3-PI3K-Akt axis.

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Fulvestrant-mediated mTOR upregulation requires signaling through the Er...
(A) Western blot analysis of MCF7, CAMA-1, T47D, and HCC1428, whole-cell lysates harvested from serum-deprived cells after treatment for 48 hours with fulvestrant (1 μM), with the final 2 hours in the added presence of the mTOR inhibitor RAD001 (10 nM), the Akt inhibitor MK2206 (1 μM), the PI3K/p110α inhibitor BKM120 (0.5 μM), or the MEK inhibitor U0126 (5 μM). Antibodies used are indicated at the left of each panel. (B) Western blot analysis of MCF7 cells treated for 48 hours with fulvestrant or DMSO, and with RAD001 or DMSO for the final 2 hours of culture. Antibodies used are indicated. (C) Western blot analysis of MCF7 cells treated with fulvestrant (1 μM) or U3-1287 (5 μg/ml) for 48 hours prior to collection of whole-cell lysates. Antibodies used are indicated. (D) MCF7, T47D, and MDA-MB-361 cells were cultured 24 hours in the presence of fulvestrant (1 μM) or DMSO, U3-1287 (5 μg/ml) or control IgG, and RAD001 (0.2 μM) or DMSO. FITC-conjugated annexin V was added to the cultured medium to detect apoptotic cells. The number of FITC-labeled cells per ×600 field was measured using Scion Image 2.0 software. Values shown represent the average ± SD, n = 3. P values calculated with 1-way ANOVA. (E) RTK array was used to assess tyrosine phosphorylation of multiple RTKs in whole MCF7 tumor lysates.