Breast Tumor Kinase (Brk/PTK6) is Induced by HIF, Glucocorticoid Receptor and PELP1 Mediated Stress Signaling in Triple-Negative Breast Cancer.
By: Tarah M Regan Anderson, Shi Hong Ma, Ganesh V Raj, John A Cidlowski, Taylor M Helle, Todd P Knutson, Raisa Krutilina, Tiffany N Seagroves, Carol A Lange

Division of Hematology, Oncology, and Transplantation, Departments of Medicine and Pharmacology and The Masonic Cancer Center, University of Minnesota.
2016-1-31; doi: 10.1158/0008-5472.CAN-15-2510
Abstract

Cancer cells use stress response pathways to sustain their pathogenic behavior. In breast cancer, stress response-associated phenotypes are mediated by the breast tumor kinase, Brk (PTK6), via the hypoxia-inducible factors HIF-1α and HIF-2α. Given that glucocorticoid receptor (GR) is highly expressed in triple negative breast cancer (TNBC), we investigated crosstalk between stress hormone-driven GR signaling and HIF-regulated physiologic stress. Primary TNBC tumor explants or cell lines treated with the GR ligand dexamethasone (dex) exhibited robust induction of Brk mRNA and protein that was HIF1/2-dependent. HIF and GR co-assembled on the BRK promoter in response to either hypoxia or dex, indicating that Brk is a direct GR/HIF target. Notably, HIF-2α, not HIF-1α, expression was induced by GR signaling and the important steroid receptor coactivator PELP1 was also found to be induced in a HIF-dependent manner. Mechanistic investigations showed how PELP1 interacted with GR to activate Brk expression and demonstrated that physiologic cell stress, including hypoxia, promoted phosphorylation of GR serine 134, initiating a feed-forward signaling loop that contributed significantly to Brk upregulation. Collectively, our findings linked cellular stress (HIF) and stress hormone (cortisol) signaling in TNBC, identifying the phospho-GR/HIF/PELP1 complex as a potential therapeutic target to limit Brk-driven progression and metastasis in TNBC patients.



Copyright © 2016, American Association for Cancer Research.

PMID:26825173






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