Wu et al. map an Nf1-Stat3-Arid1b/ b-catenin pathway that initiates
Neurofibromatosis type 1 (Nf1) neurofibromas, using unbiased
insertional mutagenesis screening. Stat3 transcriptionally represses Gsk3b and Arid1b, thereby activating b-catenin in Schwann cell precursors and resulting in neurofibroma initiation and maintenance.
Stat3-mediated modification plays a role in early tumorigenesis.
PM-18. EGFR-STAT3 ACTIVATES b-CATENIN SIGNALING TO
DRIVE NEUROFIBROMA INITIATION IN NF1, AND PLAYS A
ROLE IN TUMOR MAINTENANCE
Nancy Ratner1, Vincent Keng2, Deanna M. Patmore1, Jed K. Kendall1,
Edwin Jousma1, Kwangmin Choi1, Danhua Fan2, Eric B. Schwartz2, James
R. Fuchs2, Yuanshu Zou2, Mi-Ok Kim1, Eva Dombi5, David E. Levy6, Jose
A. Cancelas1, Anat Stemmer-Rachamimov4, Robert J. Spinner3, and David
A. Largaespada2;
1
Cincinnati Children’s, Cincinnati, OH, USA; 2
University of
Minnesota, Minneapolis, MN, USA; 3
Mayo Clinic, Rochester, MN, USA; 4
Massachusetts General Hospital, Boston, MA, USA; 5
National Cancer
Institute Pediatric Branch, Bethesda, MD, USA; 6
New York University School
of Medicine, New York, NY, USA
To identify genes and signaling pathways that drive peripheral nerve tumor
initiationand growth beyond the Ras-MAPK pathwaywe used unbiased insertional
mutagenesis screening. We identified Stat3 as a potential driver of
Neurofibromatosis type 1 neurofibroma. Targeted genetic deletion of Stat3
in Schwann cell precursors (SCPs) and Schwann cells (SCs) largely prevented
neurofibroma formation, and self-renewal of tumor initiating cells. Genetic
gain- and loss-of-function identified EGFR as the major upstream regulator
of P-Stat3 in mouse and human neurofibroma SCP and in neurofibroma initiation;
IL-6 reinforced EGFR/Jak/Stat signaling. Preclinical tests of a Jak2/
Stat3 inhibitor reduced established neurofibroma growth, supporting an additional
role for Stat3 in benign nerve tumor maintenance. Unexpectedly, downstream
of Stat3, we identified b-catenin, and b-catenin expression rescued
phenotypic effects of Stat3 loss in SCPs. Phosphorylated STAT3 (Y705) and
b-catenin were strongly correlated in NF1 human plexiform neurofibromas.
The data support testing of JAK/STAT inhibition and Wnt/ b-catenin
pathway inhibition in neurofibroma therapeutic trials. Supported by: NIH
R01 NS28840 to N.R. and NIH P50 NS057531 to N.R. and D.L.), a
DAMD New Investigator Award (W81XWH-11-1-0259) and an Ohio State
University Comprehensive Cancer Center Pelotonia Idea Grant (to J.W.).
The American Cancer Society (IRG-67-003-44) supported J.R.F.
Overnight, room temperature hold
(ONH) of whole blood before component processing
offers several benefits. This study evaluated the storage
and in vivo recovery characteristics of ONH red blood
cells (RBCs) stored in additive solution-7 (AS-7).
Patients in organ failure of vascular origin have increased circulating hematopoietic stem cells and
progenitors (HSC/P). Plasma levels of angiotensin II (Ang-II), are commonly increased in
vasculopathies. Hyperangiotensinemia results in activation of a very distinct Ang-II receptor set,
Rho-family GTPase members, and actin in bone marrow endothelial cells (BMEC) and HSC/P,
which results in decreased membrane integrin activation in both BMEC and HSC/P, and in HSC/P
de-adhesion and mobilization. The Ang-II effect can be reversed pharmacologically and
genetically by inhibiting Ang-II production or signaling through BMEC AT2R, HSCP AT1R/
AT2R or HSC/P RhoA, but not by interfering with other vascular tone mediators.
Hyperangiotensinemia and high counts of circulating HSC/P seen in sickle cell disease (SCD) as a
result of vascular damage, is significantly decreased by Ang-II inhibitors. Our data define for the
first time the role of Ang-II HSC/P traffic regulation and redefine the hematopoietic consequences
of anti-angiotensin therapy in SCD.
Chromosome 5q deletions (del[5q]) are common in
high-risk (HR) myelodysplastic syndrome (MDS) and
acute myeloid leukemia (AML); however, the gene
regulatory networks that sustain these aggressive
diseases are unknown. Reduced miR-146a expression
in del(5q) HR MDS/AML and miR-146a/ hematopoietic
stem/progenitor cells (HSPCs) results in
TRAF6/NF-kB activation. Increased survival and proliferation
of HSPCs from miR-146alow HR MDS/AML is
sustained by a neighboring haploid gene, SQSTM1
(p62), expressed from the intact 5q allele. Overexpression
of p62 from the intact allele occurs through
NF-kB-dependent feedforward signaling mediated
by miR-146a deficiency. p62 is necessary for
TRAF6-mediated NF-kB signaling, as disrupting the
p62-TRAF6 signaling complex results in cell-cycle arrest
and apoptosis of MDS/AML cells. Thus, del(5q)
HR MDS/AML employs an intrachromosomal gene
network involving loss of miR-146a and haploid overexpression
of p62 via NF-kB to sustain TRAF6/NF-kB
signaling for cell survival and proliferation. Interfering
with the p62-TRAF6 signaling complex represents a
therapeutic option in miR-146a-deficient and aggressive
del(5q) MDS/AML.
Severe congenital neutropenia (SCN) is often associated with inherited heterozygous point mutations in ELANE, which
encodes neutrophil elastase (NE). However, a lack of appropriate models to recapitulate SCN has substantially hampered
the understanding of the genetic etiology and pathobiology of this disease. To this end, we generated both normal and SCN
patient–derived induced pluripotent stem cells (iPSCs), and performed genome editing and differentiation protocols that
recapitulate the major features of granulopoiesis. Pathogenesis of ELANE point mutations was the result of promyelocyte
death and differentiation arrest, and was associated with NE mislocalization and activation of the unfolded protein
response/ER stress (UPR/ER stress). Similarly, high-dose G-CSF (or downstream signaling through AKT/BCL2) rescues
the dysgranulopoietic defect in SCN patient–derived iPSCs through C/EBPβ-dependent emergency granulopoiesis. In
contrast, sivelestat, an NE-specific small-molecule inhibitor, corrected dysgranulopoiesis by restoring normal intracellular
NE localization in primary granules; ameliorating UPR/ER stress; increasing expression of CEBPA, but not CEBPB; and
promoting promyelocyte survival and differentiation. Together, these data suggest that SCN disease pathogenesis includes
NE mislocalization, which in turn triggers dysfunctional survival signaling and UPR/ER stress. This paradigm has the
potential to be clinically exploited to achieve therapeutic responses using lower doses of G-CSF combined with targeting to
correct NE mislocalization.