Inhibition of fibroblast growth by Notch1 signaling is mediated by induction of Wnt11-dependent WISP-1.
Fibroblasts are an integral component of stroma and important source of growth factors and extracellular matrix (ECM). They play a prominent role in maintaining tissue homeostasis and in wound healing and tumor growth. Notch signaling regulates biological function in a variety of cells. To elucidate the physiological function of Notch signaling in fibroblasts, we ablated Notch1 in mouse (Notch1(Flox/Flox)) embryonic fibroblasts (MEFs). Notch1-deficient (Notch1(-/-)) MEFs displayed faster growth and motility rate compared to Notch1(Flox/Flox) MEFs. Such phenotypic changes, however, were reversible by reconstitution of Notch1 activation via overexpression of the intracellular domain of Notch1 (NICD1) in Notch1-deficient MEFs. In contrast, constitutive activation of Notch1 signaling by introducing NICD1 into primary human dermal fibroblasts (FF2441), which caused pan-Notch activation, inhibited cell growth and motility, whereas cellular inhibition was relievable when the Notch activation was countered with dominant-negative mutant of Master-mind like 1 (DN-MAML-1). Functionally, "Notch-activated" stromal fibroblasts could inhibit tumor cell growth/invasion. Moreover, Notch activation induced expression of Wnt-induced secreted proteins-1 (WISP-1/CCN4) in FF2441 cells while deletion of Notch1 in MEFs resulted in an opposite effect. Notably, WISP-1 suppressed fibroblast proliferation, and was responsible for mediating Notch1's inhibitory effect since siRNA-mediated blockade of WISP-1 expression could relieve cell growth inhibition. Notch1-induced WISP-1 expression appeared to be Wnt11-dependent, but Wnt1-independent. Blockade of Wnt11 expression resulted in decreased WISP-1 expression and liberated Notch-induced cell growth inhibition. These findings indicated that inhibition of fibroblast proliferation by Notch pathway activation is mediated, at least in part, through regulating Wnt1-independent, but Wnt11-dependent WISP-1 expression.
Department of Surgery, Miller School of Medicine, University of Miami, Miami, Florida, United States of America.
Zhao-Jun
ZJ
Liu
Yan
Y
Li
Yurong
Y
Tan
Min
M
Xiao
Jialin
J
Zhang
Freddy
F
Radtke
Omaida C
OC
Velazquez
D000818:Animals; D055511:CCN Intercellular Signaling Proteins / Q000096:biosynthesis* / Q000235:genetics; D002460:Cell Line; D049109:Cell Proliferation / Q000502:physiology*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D051379:Mice; D009154:Mutation; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism*; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*; D060449:Wnt Signaling Pathway / Q000502:physiology*
D055511:CCN Intercellular Signaling Proteins; C116396:CCN4 protein, human; C492067:CCN4 protein, mouse; C497761:NOTCH1 protein, human; C497762:Notch1 protein, mouse; D011518:Proto-Oncogene Proteins; D051881:Receptor, Notch1; D051153:Wnt Proteins; C540523:Wnt11 protein, human; C508957:Wnt11 protein, mouse