Hunk is required for HER2/neu-induced mammary tumorigenesis
Elizabeth S. Yeh, … , Robert D. Cardiff, Lewis A. Chodosh
Elizabeth S. Yeh, … , Robert D. Cardiff, Lewis A. Chodosh
Published February 14, 2011
Citation Information: J Clin Invest. 2011;121(3):866-879. https://doi.org/10.1172/JCI42928.
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Research Article Oncology

Hunk is required for HER2/neu-induced mammary tumorigenesis

Abstract

Understanding the molecular pathways that contribute to the aggressive behavior of human cancers is a critical research priority. The SNF1/AMPK-related protein kinase Hunk is overexpressed in aggressive subsets of human breast, ovarian, and colon cancers. Analysis of Hunk–/– mice revealed that this kinase is required for metastasis of c-myc–induced mammary tumors but not c-myc–induced primary tumor formation. Similar to c-myc, amplification of the proto-oncogene HER2/neu occurs in 10%–30% of breast cancers and is associated with aggressive tumor behavior. By crossing Hunk–/– mice with transgenic mouse models for HER2/neu-induced mammary tumorigenesis, we report that Hunk is required for primary tumor formation induced by HER2/neu. Knockdown and reconstitution experiments in mouse and human breast cancer cell lines demonstrated that Hunk is required for maintenance of the tumorigenic phenotype in HER2/neu-transformed cells. This requirement is kinase dependent and resulted from the ability of Hunk to suppress apoptosis in association with downregulation of the tumor suppressor p27kip1. Additionally, we find that Hunk is rapidly upregulated following HER2/neu activation in vivo and in vitro. These findings provide what we believe is the first evidence for a role for Hunk in primary tumorigenesis and cell survival and identify this kinase as an essential effector of the HER2/neu oncogenic pathway.

Authors

Elizabeth S. Yeh, Thomas W. Yang, Jason J. Jung, Heather P. Gardner, Robert D. Cardiff, Lewis A. Chodosh

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Figure 5

Expression of a kinase-dead allele of Hunk impairs growth of HER2/neu-induced tumors.

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Expression of a kinase-dead allele of Hunk impairs growth of HER2/neu-in...
(A) Western blot analysis confirming expression of HER2/neu, Hunk–wild-type, and Hunk-K91M in HC11 cells. Left panel shows a longer autoradiographic exposure to illustrate the previously observed increase in endogenous Hunk levels in empty vector cells expressing HER2/neu. (B) Gross comparison of tumors derived from HC11;Hunk–wild-type and HC11;Hunk-K91M cells sacrificed at the same time after injection. Average volume of wild-type Hunk–derived tumors was 237.9 mm3, compared with 15.5 mm3 for Hunk-K91M–derived tumors. White arrows indicate tumors. (C) Mean tumor growth rates of tumors derived from HC11;vector control–, HC11;Hunk–wild-type–, or HC11;Hunk-K91M–expressing cells. **P < 0.01, Hunk–wild-type versus Hunk-K91M. Data represent mean ± SEM. (D) Western blot analysis for Hunk in MMTV-neu;Hunk–deficient cells reconstituted with vector control, Hunk–wild-type, or Hunk-K91M. (E) Mean tumor growth rate of orthotopic tumors derived from MMTV-neu;Hunk–deficient cells reconstituted with Hunk–wild-type, Hunk-K91M, or vector control. *P < 0.01, control versus Hunk–wild-type; **P < 0.001, Hunk–wild-type versus Hunk-K91M. Data represent mean ± SEM.