The receptor tyrosine kinase EphA2 promotes mammary adenocarcinoma tumorigenesis and metastatic progression in mice by amplifying ErbB2 signaling
Dana M. Brantley-Sieders, … , Rebecca S. Muraoka-Cook, Jin Chen
Dana M. Brantley-Sieders, … , Rebecca S. Muraoka-Cook, Jin Chen
Published December 13, 2007
Citation Information: J Clin Invest. 2008;118(1):64-78. https://doi.org/10.1172/JCI33154.
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Research Article Oncology

The receptor tyrosine kinase EphA2 promotes mammary adenocarcinoma tumorigenesis and metastatic progression in mice by amplifying ErbB2 signaling

Abstract

Overexpression of the receptor tyrosine kinase EPH receptor A2 (EphA2) is commonly observed in aggressive breast cancer and correlates with a poor prognosis. However, while EphA2 has been reported to enhance tumorigenesis, proliferation, and MAPK activation in several model systems, other studies suggest that EphA2 activation diminishes these processes and inhibits the activity of MAPK upon ligand stimulation. In this study, we eliminated EphA2 expression in 2 transgenic mouse models of mammary carcinoma. EphA2 deficiency impaired tumor initiation and metastatic progression in mice overexpressing ErbB2 (also known as Neu) in the mammary epithelium (MMTV-Neu mice), but not in mice overexpressing the polyomavirus middle T antigen in mammary epithelium (MMTV–PyV-mT mice). Histologic and ex vivo analyses of MMTV-Neu mouse mammary epithelium indicated that EphA2 enhanced tumor proliferation and motility. Biochemical analyses revealed that EphA2 formed a complex with ErbB2 in human and murine breast carcinoma cells, resulting in enhanced activation of Ras-MAPK signaling and RhoA GTPase. Additionally, MMTV-Neu, but not MMTV–PyV-mT, tumors were sensitive to therapeutic inhibition of EphA2. These data suggest that EphA2 cooperates with ErbB2 to promote tumor progression in mice and may provide a novel therapeutic target for ErbB2-dependent tumors in humans. Moreover, EphA2 function in tumor progression appeared to depend on oncogene context, an important consideration for the application of therapies targeting EphA2.

Authors

Dana M. Brantley-Sieders, Guanglei Zhuang, Donna Hicks, Wei Bin Fang, Yoonha Hwang, Justin M.M. Cates, Karen Coffman, Dowdy Jackson, Elizabeth Bruckheimer, Rebecca S. Muraoka-Cook, Jin Chen

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Figure 1

EphA2 deficiency reduces mammary tumorigenesis, metastasis, proliferation, and vascularity in MMTV-Neu mice.

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EphA2 deficiency reduces mammary tumorigenesis, metastasis, proliferatio...
(A) Number of surface lung lesions was significantly reduced in EphA2–/– MMTV-Neu mice (P < 0.05; single-factor ANOVA). Data are mean ± SEM. (B) Top: Whole-mount mammary gland preparations (8 mo) revealed diminished hyperplasia in EphA2–/– glands relative to controls. Shown are an EphA2+/+ gland with pervasive epithelial hyperplasia (left) and an EphA2+/– gland with a small tumor (arrowhead; middle). Asterisks indicate inguinal lymph node. Bottom: H&E-stained mammary gland sections (8 mo) reveal reduced epithelial cell content in EphA2–/– MMTV-Neu tissue samples relative to controls. Scale bar: 250 μm. (C) Top: Mammary epithelial proliferation (PCNA+ nuclei; arrowheads), was significantly reduced (P < 0.05; 2-tailed, paired Student’s t test). Scale bar: 50 μm. Bottom: Mammary epithelial apoptosis (TUNEL+ nuclei; arrowheads) was not affected. (D) Top: Proliferation of primary mammary epithelial cells from EphA2–/– animals (BrdU incorporation; arrowheads) was reduced relative to EphA2+/+ cells (P < 0.05; 2-tailed, paired Student’s t test). Bottom: Apoptosis (TUNEL+ nuclei; arrowheads) was significantly increased in EphA2–/– primary mammary epithelial cells relative to controls (P < 0.05; 2-tailed, paired Student’s t test). Scale bar: 20 μm. (E) H&E-stained tumor sections (1 yr) demonstrate increased cystic degeneration and lumen formation in EphA2–/– tumors. Scale bar: 250 μm. (F) Decreased tumor cell proliferation (PCNA+ nuclei; arrowheads) was observed for EphA2–/– MMTV-Neu tumors compared with controls (P < 0.05; single-factor ANOVA). Scale bar: 50 μm. (G) Microvascular density (CD31+ vessels; arrowheads) was significantly reduced in EphA2–/– MMTV-Neu tumors relative to controls (P < 0.05; single-factor ANOVA). Scale bar: 100 μm.