PEAK1 Acts as a Molecular Switch to Regulate Context-Dependent TGFβ Responses in Breast Cancer.
Transforming Growth Factor β (TGFβ) has dual functions as both a tumor suppressor and a promoter of cancer progression within the tumor microenvironment, but the molecular mechanisms by which TGFβ signaling switches between these outcomes and the contexts in which this switch occurs remain to be fully elucidated. We previously identified PEAK1 as a new non-receptor tyrosine kinase that associates with the cytoskeleton, and facilitates signaling of HER2/Src complexes. We also showed PEAK1 functions downstream of KRas to promote tumor growth, metastasis and therapy resistance using preclinical in vivo models of human tumor progression. In the current study, we analyzed PEAK1 expression in human breast cancer samples and found PEAK1 levels correlate with mesenchymal gene expression, poor cellular differentiation and disease relapse. At the cellular level, we also observed that PEAK1 expression was highest in mesenchymal breast cancer cells, correlated with migration potential and increased in response to TGFβ-induced epithelial-mesenchymal transition (EMT). Thus, we sought to evaluate the role of PEAK1 in the switching of TGFβ from a tumor suppressing to tumor promoting factor. Notably, we discovered that high PEAK1 expression causes TGFβ to lose its anti-proliferative effects, and potentiates TGFβ-induced proliferation, EMT, cell migration and tumor metastasis in a fibronectin-dependent fashion. In the presence of fibronectin, PEAK1 caused a switching of TGFβ signaling from its canonical Smad2/3 pathway to non-canonical Src and MAPK signaling. This report is the first to provide evidence that PEAK1 mediates signaling cross talk between TGFβ receptors and integrin/Src/MAPK pathways and that PEAK1 is an important molecular regulator of TGFβ-induced tumor progression and metastasis in breast cancer. Finally, PEAK1 overexpression/upregulation cooperates with TGFβ to reduce breast cancer sensitivity to Src kinase inhibition. These findings provide a rational basis to develop therapeutic agents to target PEAK1 expression/function or upstream/downstream pathways to abrogate breast cancer progression.
Department of Biology, California State University Northridge, Northridge, CA 91330, United States of America.
Megan
M
Agajanian
Department of Biology, California State University Northridge, Northridge, CA 91330, United States of America.
Anaamika
A
Campeau
Department of Biology, California State University Northridge, Northridge, CA 91330, United States of America.
Malachia
M
Hoover
Department of Biology, California State University Northridge, Northridge, CA 91330, United States of America; Department of Biology, Georgetown University, Washington, DC 20057, United States of America.
Alexander
A
Hou
Department of Biology, California State University Northridge, Northridge, CA 91330, United States of America.
Daniel
D
Brambilla
Department of Biology, California State University Northridge, Northridge, CA 91330, United States of America.
Sa La
SL
Kim
Department of Pathology & Moores Cancer Center, University of California San Diego, La Jolla, CA 92093, United States of America.
Richard L
RL
Klemke
Department of Biology, California State University Northridge, Northridge, CA 91330, United States of America.
Jonathan A
JA
Kelber
D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects; D006801:Humans; D061986:MCF-7 Cells; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D016212:Transforming Growth Factor beta; C573947:PEAK1 protein, human; D011505:Protein-Tyrosine Kinases