The receptor tyrosine kinase EphA2 promotes mammary adenocarcinoma tumorigenesis and metastatic progression in mice by amplifying ErbB2 signaling
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
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
View: Text | PDF
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

×

Figure 6

EphA2 physically and functionally interacts with ErbB2.

Options: View larger image (or click on image) Download as PowerPoint
EphA2 physically and functionally interacts with ErbB2. (A) COS7 cells w...
(A) COS7 cells were transfected with plasmids for expression of EphA2 or/and ErbB2. EphA2 or ErbB2 was immunoprecipitated from cell lysates, and products were analyzed for ErbB2 or/and EphA2. Coexpression of EphA2 and ErbB2 was sufficient to permit coimmunoprecipitation. (B) Endogenous ErbB2 and EphA2 were coimmunoprecipitated with anti-EphA2 or anti-ErbB2 antibodies, respectively, in EphA2+/+ MMTV-Neu tumor cells that were untreated or treated with the chemical crosslinker DTSSP. The interaction detected was specific: EphA2 and ErbB2 were not immunoprecipitated by control IgG. Uniform input was validated by probing lysates for expression of EphA2 and ErbB2. (C) COS7 cells were transfected with plasmids for expression of EphA2 or ErbB2. EphA2 was immunoprecipitated from cell lysates, and products were analyzed for EphA2 expression and tyrosine phosphorylation. Coexpression of ErbB2 and EphA2 was sufficient to induce phosphorylation of EphA2 in COS7 cells in the absence of ephrin ligand stimulation. (D) Interaction between EphA2 and HER2 in MCF10A cells overexpressing HER2 was observed, as EphA2 and HER2 were coimmunoprecipitated with anti-EphA2 antibodies in HER2-overexpressing cells, but not in parental MCF10A cells. Elevated EphA2 phosphorylation was observed in MCF10A cells overexpressing HER2 relative to parental MCF10A cells, and treatment with the ErbB2 kinase inhibitor AG825 reduced EphA2 phosphorylation as well as ErbB2 phosphorylation in MCF10A cells overexpressing HER2.