Phosphorylation of serine 367 of FOXC2 by p38 regulates ZEB1 and breast cancer metastasis, without impacting primary tumor growth.
Metastatic competence is contingent upon the aberrant activation of a latent embryonic program, known as the epithelial-mesenchymal transition (EMT), which bestows stem cell properties as well as migratory and invasive capabilities upon differentiated tumor cells. We recently identified the transcription factor FOXC2 as a downstream effector of multiple EMT programs, independent of the EMT-inducing stimulus, and as a key player linking EMT, stem cell traits and metastatic competence in breast cancer. As such, FOXC2 could serve as a potential therapeutic target to attenuate metastasis. However, as FOXC2 is a transcription factor, it is difficult to target by conventional means such as small-molecule inhibitors. Herein, we identify the serine/threonine-specific kinase p38 as a druggable upstream regulator of FOXC2 stability and function that elicits phosphorylation of FOXC2 at serine 367 (S367). Using an orthotopic syngeneic mouse tumor model, we make the striking observation that inhibition of p38-FOXC2 signaling selectively attenuates metastasis without impacting primary tumor growth. In this model, circulating tumor cell numbers are significantly reduced in mice treated with the p38 inhibitor SB203580, relative to vehicle-treated counterparts. Accordingly, genetic or pharmacological inhibition of p38 decreases FOXC2 protein levels, reverts the EMT phenotype and compromises stem cell attributes in vitro. We also identify the EMT-regulator ZEB1-known to directly repress E-cadherin/CDH1-as a downstream target of FOXC2, critically dependent on its activation by p38. Consistent with the notion that activation of the p38-FOXC2 signaling axis represents a critical juncture in the acquisition of metastatic competence, the phosphomimetic FOXC2(S367E) mutant is refractory to p38 inhibition both in vitro and in vivo, whereas the non-phosphorylatable FOXC2(S367A) mutant fails to elicit EMT and upregulate ZEB1. Collectively, our data demonstrate that FOXC2 regulates EMT, stem cell traits, ZEB1 expression and metastasis in a p38-dependent manner, and attest to the potential utility of p38 inhibitors as antimetastatic agents.
Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
S J
SJ
Werden
Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
N
N
Sphyris
Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
T R
TR
Sarkar
Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
A N
AN
Paranjape
Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
A M
AM
LaBaff
Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
J H
JH
Taube
Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
B G
BG
Hollier
Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
E Q
EQ
Ramirez-Peña
Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
R
R
Soundararajan
Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
P
P
den Hollander
Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
E
E
Powell
Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
G V
GV
Echeverria
Department of Biochemistry, Hamamatsu University School of Medicine, Hamamatsu, Japan.
N
N
Miura
Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, TX, USA.
J T
JT
Chang
Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
H
H
Piwnica-Worms
Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA.|Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA.
J M
JM
Rosen
Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.|Metastasis Research Center, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.|Center for Stem Cell and Developmental Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
S A
SA
Mani
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004195:Disease Models, Animal; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics; D005260:Female; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D064593:Heterografts; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000378:metabolism; D051379:Mice; D009362:Neoplasm Metastasis; D014411:Neoplastic Stem Cells / Q000378:metabolism; D010641:Phenotype; D010766:Phosphorylation; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D012694:Serine / Q000378:metabolism*; D000071799:Zinc Finger E-box-Binding Homeobox 1 / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D000970:Antineoplastic Agents; D051858:Forkhead Transcription Factors; D034741:RNA, Small Interfering; D000071799:Zinc Finger E-box-Binding Homeobox 1; C082078:mesenchyme fork head 1 protein; D012694:Serine; D048051:p38 Mitogen-Activated Protein Kinases