Download RUNX1 Modulates TGF-β1-Induced Myofibroblast Differentiation in

RUNX1 Modulates TGF-β1-Induced Myofibroblast Differentiation
in Human Prostate-Derived Mesenchymal Stem Cells
Woosook Kim, David Barron, Rebeca San Martin, and David Rowley
Baylor College of Medicine, Houston, TX
Reactive stroma in prostate cancer is typified by the co-evolution of
myofibroblasts. This reactive stroma is associated with most human carcinoma
and more reactive stroma is predictive of aggressive disease progression. TGFβ1 is a key factor in regulating reactive stroma biology. However, the origin of
myofibroblasts and the mechanisms of how TGF-β1 recruits, activates, and
induces their differentiation are essentially unknown. We have identified
mesenchymal stem cells from normal human prostate gland and evaluated their
biology in a novel 3D co-culture system. Human prostate-derived mesenchymal
stem cells (hpMSCs) were CD44+CD90+ and exhibited multilineage differentiation
potential. When co-cultured with LNCaP prostate cancer cells or co-inoculated in
nude mice, self-organizing organoids formed with a core of stromal cells and a
peripheral mantel of LNCaP cells. To investigate the role of TGF-β1, hpMSCs
were co-cultured with LNCaP cells engineered to overexpress active TGF-β1.
LNCaP cells overexpressing TGF-β1 induced hpMSC differentiation to
prototypical reactive stroma myofibroblasts and expression of TGF-β1 in LNCaP
cells led to differential gene expression in hpMSCs. Of those gene expression
profiles, RUNX1 was identified as a key transcription factor in hpMSC that
mediates TGF-β1-induced myofibroblast differentiation. Knockdown of RUNX1 in
hpMSC significantly promoted differentiation to myofibroblasts. Conversely,
overexpression of RUNX1 inhibited a myofibroblast gene expression signature.
Furthermore, RUNX1 repression in hpMSC completely halted cellular
proliferation by inducing G2/M phase cell cycle arrest. Together, our data show
that reactive stroma in prostate cancer initiates from activation and differentiation
of CD44+CD90+ endogenous hpMSCs. Moreover, our data indicate that RUNX1
is required for transit-amplifying cell proliferation to gain a critical mass of
myofibroblasts that results in a tumor-promoting reactive stroma. Therefore,
RUNX1 functions as a key modulator of reactive stroma formation in cancer by
playing a permissive role in cell proliferation.