Osteoglycin promotes meningioma development through downregulation of NF2 and activation of mTOR signaling
Mei et al. Cell Communication and Signaling
Osteoglycin promotes meningioma development through downregulation of NF2 and activation of mTOR signaling
Yu Mei 0 3
Ziming Du 2
Changchen Hu 0 1 3
Noah F. Greenwald 0 3 7
Malak Abedalthagafi 2 6
Nathalie Y.R. Agar 0 3 7
Gavin P. Dunn 4 5
Wenya Linda Bi 0 3 7
Sandro Santagata 2
Ian F. Dunn 0 3
0 Center for Skull Base and Pituitary Surgery, Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School , Boston, MA , USA
1 Department of Neurosurgery, Shanxi Provincial People's Hospital, Shanxi Medical University , Taiyuan , China
2 Department of Pathology, Brigham and Women's Hospital, Harvard Medical School , Boston, MA , USA
3 Center for Skull Base and Pituitary Surgery, Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School , Boston, MA , USA
4 Center for Human Immunology and Immunotherapy Programs, Washington University School of Medicine , St. Louis, MO , USA
5 Department of Neurosurgery, Washington University School of Medicine , St. Louis, MO , USA
6 Saudi Human Genome Laboratory, King Fahad Medical City and King Abdulaziz City for Science and Technology , Riyadh , Saudi Arabia
7 Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School , Boston, MA , USA
Background: Meningiomas are the most common primary intracranial tumors in adults. While a majority of meningiomas are slow growing neoplasms that may cured by surgical resection, a subset demonstrates more aggressive behavior and insidiously recurs despite surgery and radiation, without effective alternative treatment options. Elucidation of critical mitogenic pathways in meningioma oncogenesis may offer new therapeutic strategies. We performed an integrated genomic and molecular analysis to characterize the expression and function of osteoglycin (OGN) in meningiomas and explored possible therapeutic approaches for OGN-expressing meningiomas. Methods: OGN mRNA expression in human meningiomas was assessed by RNA microarray and RNAscope. The impact of OGN on cell proliferation, colony formation, and mitogenic signaling cascades was assessed in a human meningioma cell line (IOMM-Lee) with stable overexpression of OGN. Furthermore, the functional consequences of introducing an AKT inhibitor in OGN-overexpressing meningioma cells were assessed. Results: OGN mRNA expression was dramatically increased in meningiomas compared to a spectrum of other brain tumors and normal brain. OGN-overexpressing meningioma cells demonstrated an elevated rate of cell proliferation, cell cycle activation, and colony formation as compared with cells transfected with control vector. In addition, NF2 mRNA and protein expression were both attenuated in OGN-overexpressing cells. Conversely, mTOR pathway and AKT activation increased in OGN-overexpressing cells compared to control cells. Lastly, introduction of an AKT inhibitor reduced OGN expression in meningioma cells and resulted in increased cell death and autophagy, suggestive of a reciprocal relationship between OGN and AKT. Conclusion: We identify OGN as a novel oncogene in meningioma proliferation. AKT inhibition reduces OGN protein levels in meningioma cells, with a concomitant increase in cell death, which provides a promising treatment option for meningiomas with OGN overexpression.
Osteoglycin; Autophagy; AKT inhibitor; Meningioma; Neurofibromatosis type 2; Mammalian target of rapamycin complex 1
Meningiomas represent approximately one-third of all
primary brain tumors in adults and arise from the
meninges surrounding the brain and spinal cord [
World Health Organization (WHO) classifies
meningiomas as grade I (benign), grade II (atypical), and grade
III (anaplastic/malignant), with 15 histologic subtypes
]. Most meningiomas are benign (90% grade I) and
slow growing, with effective control following surgical
resection if treatment is indicated. However, grade II-III
meningiomas and those located at the skull base offer a
management challenge due to their predilection for
recurrence and premature morbidity and mortality from
disease, despite surgery and radiation. The lack of
effective pharmacotherapeutic options motivates further
definition of meningioma biology to provide alternative
strategies for treatment.
Meningiomas represent one of the first tumors to be
associated with a genomic driver with the discovery that
Neurofibromatosis 2 (NF2), an inherited genetic disorder
characterized by the development of schwannomas and
meningiomas, arose in the setting of mutations of the
NF2 gene [
]. Recent next-generation genomic analysis
of meningiomas revealed additional recurrent mutations
in v-akt murine thymoma viral oncogene homolog 1/3
(AKT1/3), phosphoinositide-3-kinase catalytic alpha
polypeptide (PIK3CA), smoothened (SMO), homolog of
suppressor of fused (SUFU), TNF receptor-associated
factor 7 (TRAF7), krupplelike factor 4 (KLF4), SWI/SNF
related, matrix associated, actin dependent regulator of
chromatin, subfamily b, member 1 (SMARCB1), RNA
polymerase II subunit A (POLR2A), telomerase reverse
transcriptase (TERT) promoter, and BRCA1 associated
protein 1 (BAP1) [
]. These, as well as loss of
Merlin, the protein product of NF2, are additionally
associated with downstream activation of mitogenic
pathways such as the mTOR and Hedgehog cascades, to
produce uncontrolled neoplastic growth [
the precise mechanisms by which meningioma
oncogenesis occurs remains incompletely understood.
Osteoglycin (OGN), located on 9q22.31, plays critical
roles in both physiological condition, such as the
formation of bone [
] and normal vasculature [
], as well
as pathological processes including vascular differentiation
and remodeling . Cytokines associated with vascular
injury, such as basic fibroblast growth factor, transforming
growth factor-beta, platelet-derived growth factor and
angiotensin II, downregulate OGN gene expression [
Furthermore, OGN is a major regulator of ventricular
]. However, whether OGN is involved in
meningioma development is currently unknown.
We performed an integrated genomic and molecular
analysis to define the expression of OGN in meningiomas,
illustrate how OGN may contribute to meningioma cell growth
through interaction with other drivers of meningioma
formation such as NF2, AKT, and mTOR, and explore possible
therapeutic approaches for OGN-expressing meningiomas.
Expression profiling of OGN in human meningiomas
The expression profiling data were normalized from
publicly available datasets cataloged in GEO (Gene
Expression Omnibus) that had been acquired on Affymetrix
Human Genome U133 Plus 2.0 Array Platform
[HGU133_Plus_2], as previously described [
]. The following
datasets were used: GSE16155 (ependymoma), GSE16581
(meningioma), GSE34824 (pediatric glioblastoma),
GSE36245 (adult glioblastoma), GSE33331 (adult
astrocytoma), GSE35493 (atypical, teratoid, rhabdoid tumors/
ATRT; medulloblastoma) GSE19404 (primitive
neuroectodermal tumor), GSE34771 (CNS lymphoma), GSE5675
RNA scope in situ hybridization
Formalin-fixed, paraffin-embedded human meningioma
specimens were collected from the Department of
Pathology, Brigham and Women’s Hospital, with
corresponding clinical records and pathology reports.
Hematoxylin and eosin stained sections corresponding
to each tumor were reviewed by two neuropathologists
(SS, MA) for selection of specimens with greater than
70% estimated tumor purity. Two hundred seven
meningiomas (with triplicate cores, spanning 621 samples
total) were compiled in tissue microarray (TMA) format
for subsequent analysis. The study was approved by the
Institutional Review Boards of Brigham and Women’s
Hospital and Dana Farber Cancer Institute, Harvard
Medical School. In situ detection of OGN transcripts in
meningioma TMA was performed using RNAscope®
assay with Probe-Hs-OGN (Cat# 498831, Advanced Cell
Diagnostics, Newark, USA) and RNAscope® 2.0 HD
Reagent Kit (Cat# 310035, Advanced Cell Diagnostics)
following manufacturer protocols. All slides were digitally
scanned using Carl Zeiss Microimaging (Jena, Germany).
RNAscope staining was quantified by NIH ImageJ
software (Bethesda, USA). Single DAB stained images were
obtained using color deconvolution as previously
]. After adjustment of the color threshold,
the intensity of the DAB-positive staining was measured.
Optical density-log (max intensity/mean intensity) was
used for statistical analysis.
Human meningioma cell line culture
The human meningioma cell line IOMM-Lee (derived
from a grade III meningioma) [
], courtesy of Dr.
Randy Jensen (University of Utah), was cultured in
growth media composed of RPMI 1640 Medium, 10%
fetal bovine serum, 2 mM L-glutamine, 100 IU/mL of
penicillin, and 100 μg/mL of streptomycin (Life
Technology, Grand Island, USA). Cultured cells were maintained
at 37° in a 5% CO2 atmosphere.
OGN expressing stable cell line generation
IOMM-Lee cells were plated in 12-well plates at a
density of 200,000 cells/well, and transfected with pCMV/
Control Vector (C-terminal Fc-Myc-tagged) or pCMV/
OGN Vector (Myc-tagged) (Sino Biological, Beijing,
China). At 48 h after transfection, cells were trypsinized
and plated in 96-well plates for selection. Monoclonal
populations with stable expression of control vector
(Control-IOMM) or OGN (OGN-IOMM) were selected
with addition of hygromycin B (0.2 g/ml). Gene stability
was verified for at least ten passages by analysis of OGN
mRNA and protein expression.
Cell proliferation assay
Meningioma cells with and without OGN expression
were assessed for proliferation using the WST-1 assay
(Roche, Indianapolis, USA), which is a nonradioactive
method to quantify cell proliferation and survival.
Briefly, Control-IOMM and OGN-IOMM cells were
seeded in 96-well plates at a density of 10,000 cells/well
and cultured for 72 h. Cells were then incubated with
WST-1 for 2 h. Absorbance, as a measure of cell
proliferation, was measured on an Epoch Microplate
Spectrophotometer (BioTek, Winooski, USA).
Soft agar growth assay
Control-IOMM and OGN-IOMM cells (250,000/well)
were mixed with 0.4% agarose in growth medium, plated
on top of a solidified layer of 0.5% agarose in a 6-well
plate, and fed every 3 d with growth medium. After
18 days, the colonies were stained with 0.01% Crystal
Violet (EMD, Billerica, USA) and imaged by Zeiss
Axiovert 40 CFL Microimaging (Jena, Germany).
Colony size and number were quantified using ImageJ
(NIH, Bethesda, USA). Average colony sizes (total
colony size/total colony number) were used for
The impact of the AKT inhibitor AKTVIII and mTOR
inhibitor rapamycin (Cayman Chemical, Ann Arbor,
USA) on meningioma cells were assessed, with and
without OGN overexpression. Briefly, OGN-IOMM cells
were plated at a density of 400,000/well in 12-well plates
and treated with rapamycin (10 μM), cells were
harvested at 6 h after treatment and analyzed by
Western blot for mTOR activation and OGN expression.
OGN-IOMM cells were seeded in 96-well plates at a
density of 10,000 cells/well and treated with AKTVIII
before incubation with WST-1 for 2 h for assessment of
cytotoxic response. Serial dilutions of each drug were
tested to determine an optimal concentration for
synthetic lethality assessment at 24-72 h.
ControlIOMM and OGN-IOMM cells were treated with AKT
VIII to compare the response to inhibitor induced cell
cytotoxicity. Absorbance was determined by Epoch
Microplate Spectrophotometer (BioTek).
Furthermore, the influence of AKTVIII on signaling
pathways was assessed in OGN-expressing IOMM-Lee
meningioma cells. OGN-IOMM cells were plated at a
density of 200,000/well in 12-well plates and treated with
AKT VIII for 48 h, cells were harvested or fixed for protein
expression by Western blot or immunohistochemistry.
OGN-IOMM cells were plated at a density of 400,000/
well in 12-well plates and transfected with control
siRNA (Cat#12935-300, Thermal Fisher Scientific, Grand
Island, USA), NF2 siRNA (cat#HSS143098, Thermal
Fisher Scientific), or OGN siRNA (Cat#HSS107424,
Thermal Fisher Scientific) as described by manufacturer
protocol. Transfected cells were cultured for 24 or 48 h.
Cells were then washed with PBS and harvested for
mRNA or protein analysis.
Quantitative real-time PCR
Quantitative real-time PCR (qPCR) was performed to
assess expression of mRNA following specific culture
conditions. Total RNA was extracted with the Aurum™
Total RNA Mini Kit (Bio-Rad, Hercules, USA) and
cDNA was synthesized using the high capacity
RNA-tocDNA™ Kit (Life Technologies, Grand Island, USA)
according to manufacturer instructions. qPCR was
performed using gene-specific FAM-NFQ-conjugated
TaqMan primers for human OGN and NF2 (Thermal
Fisher Scientific). Level of mRNA expression was
normalized to β-actin. Expression was analyzed using
the comparative cycle threshold (ΔΔCT) with Applied
Biosystems 7300 Real Time PCR Software (Life
Human meningioma samples were obtained from the
Brigham and Women’s Hospital Department of
Pathology, under institutional IRB approval. Protein from
meningioma samples was extracted using RIPA buffer
(Cell Signaling, Danvers, USA). Cultured meningioma
cells with or without treatment were lysed using cell
lysis buffer (Cell Signaling, Danvers, USA). 20 μg of
protein from each sample was resolved by 4–20%
SDSPAGE (Bio-Rad), before transfer to a PVDF membrane
for overnight incubation with primary antibodies at 4 °C.
Primary antibodies were diluted at 1:1000 for OGN
(Abcam, Cambridge, USA), cyclinD1, cyclinA2, cyclinB1,
GAPDH, p-AKT(Ser473), p-mTOR (Ser2448),
p-4EBP1(Ser65), p-eIF4B (Ser422), p-eEF2K (Ser366),
pULK(Ser757), NF2, LC3IIB (Cell Signaling, Danvers,
USA). Membranes were then incubated with horseradish
peroxidase-conjugated goat anti-rabbit or goat
antimouse IgG (Cell Signaling, Danvers, USA) at 1:2000.
Blots were visualized by an ECL system (GE Healthcare,
Buckinghamshire, UK) and protein quantified by
densitometry analyses using ImageJ.
Protein expression of OGN was corroborated with
immunohistochemistry (IHC). Control-IOMM and
OGNIOMM cells were cultured for 48 h, and then were fixed
and washed with PBS. Cells were incubated with primary
antibody specific to OGN (Abcam, Cambridge, USA),
NF2 or anti-Rabbit IgG (Cell signaling, Danvers, USA),
OGN-IOMM cells treated with AKT VIII for 48 h were
fixed and incubated with anti-LC3BII, followed by
horseradish peroxidase-conjugated secondary antibody
(Vector lab, Burlingame, USA). Immunopositivity was
visualized using DAB system (Vector Lab, Burlingame,
USA). All slides were digitally scanned using Zeiss
Microimaging (Jena, Germany).
OGN correlation analysis
DNA sequencing data [
] of 35 meningiomas with
OGN RNAscope data were reviewed. These tumors were
grouped as OGN low (lower than average) and OGN
high (higher than average) according to their OGN RNA
level. The incidence of NF2 or chromosomal 22 loss
between the subgroups was compared. In addition, OGN
protein level in meningiomas with intact NF2 or NF2
loss was assessed by Western blotting.
All data obtained in vitro represent three independent
experiments. Results are expressed as mean ± standard
error. Statistical analysis was performed using Prism
(GraphPad, La Jolla, USA), and comparisons were made
with Student’s t-test, correlation, or ANOVA. A p value
< 0.05 was considered significant.
OGN gene expression is dramatically increased in human meningiomas
To determine the expression level of OGN in
meningiomas, microarray data for 9 brain tumors and normal
human brain were analyzed. As compared to negative
control (Additional file 1: Figure S1), OGN mRNA
expression was dramatically increased in meningiomas (68
samples) compared to 8 other CNS tumors and normal
brain tissue (p < 0.0001, Fig. 1a).
To confirm this finding, RNAscope was performed to
quantify OGN mRNA level in meningiomas across all
grades (126 grade I, 57 grade II, 24 grade III, Fig. 1b, p =
0.0338) and pathology subtypes (Fig. 1c). Transitional
and atypical meningiomas demonstrated the highest
levels of OGN mRNA while psammomatous
meningiomas demonstrated the lowest (Fig. 1d, p = 0.0041). In
meningiomas with known treatment status, OGN mRNA
expression levels in primary (74 samples) and recurrent
(24 samples) tumors were comparable (data not shown).
Consistent with the RNA level, OGN protein expression
was higher in meningothelial and atypical subtypes, but
lower in psammomatous and rhabdoid meningiomas as
determined by Western blotting (Fig. 1e).
OGN overexpression promotes cell proliferation and tumor cell colony formation
To determine the mitogenic effects of OGN on
meningioma cell proliferation, we stably transfected OGN
constructs into IOMM-Lee, a malignant human
meningioma cell line with minimal levels of endogenous
OGN, with confirmation of mRNA expression by qPCR
(Fig. 2a) and protein expression by Western blotting and
IHC (Fig. 2b-c).
Functional assessment of OGN overexpression in vitro
revealed a higher proliferation rate than control cells at
72 h (Fig. 2d) as well as more active tumor cell colony
formation in soft agar (Fig. 2e-f ). Corresponding to this
increased proliferative behavior, higher levels of protein
expression were observed for the cell cycle regulators
cyclin D1, A2, and B1 in OGN-overexpressing cells
compared to control cells (Fig. 2g).
Knockdown of OGN reduces cell proliferation
To confirm the mitogenic effects of OGN on cell
proliferation, OGN was knocked down in stably transfected
cells using siRNA, with significant reduction in mRNA
(Fig. 3a) at 24 h and protein expression (Fig. 3b) at 48 h
after transfection. Meningioma cells with knockdown of
OGN also demonstrated significantly reduced cell
proliferation (Fig. 3c) and expression of the cell cycle markers
cyclin A2 and cyclin B1 (Fig. 3d), compared to cells with
stable expression of OGN.
OGN downregulates NF2
Loss of function of the tumor suppressor NF2 plays
a driver role in the meningioma initiation and
]. We performed whole-exome
sequencing of the IOMM-Lee cell line and detected no
mutations in NF2 or loss of chromosome 22 [
To determine whether the effects of OGN in IOMM
cells are mediated by NF2, NF2 expression at the
transcription and translational level was evaluated by
qPCR and Western blotting following transfection of
OGN. NF2 mRNA expression was attenuated in
OGN-expressing meningioma cells (Fig. 4a), with
corresponding subsequent decrease in NF2 protein
level (Fig. 4b). Consistent with these findings, positive
immunostaining for Merlin, the protein product of
NF2, was observed in both groups, with attenuated
expression in OGN-expressing cells (Fig. 4c).
To confirm the in vitro findings, correlation analysis
of human meningioma RNA microarray data
demonstrated a significant negative correlation between NF2
mRNA and OGN mRNA (Fig. 4d). We further analyzed
35 meningiomas with the whole exome or whole
genome sequencing data [
], the frequency analysis of
genetic alteration reveals increased NF2 or chr22 loss in
human meningiomas with higher OGN mRNA
expression (Fig. 4e). To confirm the inverse relationship
between OGN and NF2, human meningiomas with intact
NF2 or NF2 loss were assessed for OGN protein
expression, revealing that meningiomas with NF2 loss express
higher levels of OGN (Fig. 4f-g).
OGN activates AKT and mTOR signaling
Several biological pathways in meningioma
oncogenesis, including loss of NF2 and mutation of AKT1,
are postulated to exhibit their oncogenic effects
through activation of the mTOR mitogenic pathway,
leading to uncontrolled neoplastic growth [
determine the effects of OGN on the mTOR complex
cascade, we analyzed the activation of proteins
involved in mTOR signaling. Western blotting
analysis indicated that the phosphorylation of mTOR
and its downstream signals, eukaryotic translation
initiation factor 4E-binding protein 1 (4E-BP1),
eukaryotic translation initiation factor 4B (eIF4B), and
eukaryotic elongation factor 2 kinase (eEF2K), were
all elevated in OGN-overexpressing meningioma lines
(Fig. 5a). Quantification of the band densitometry
confirmed significant increase in the expression of
phosphoeIF4BSer422, and phospho-eEF2KSer366 in OGN-IOMM
cells compared with their expression in control cell
lines. Conversely, introduction of the mTOR inhibitor
rapamycin (10 μM) effectively reduced mTOR
activation but did not alter OGN expression in OGN-IOMM
cells (Fig. 5b), suggesting that OGN acts upstream of
Furthermore, stable expression of OGN in
meningioma cells produced a significant increase in
phosphoAKT (Fig. 5c). This activation of AKT by OGN is not
affected by mTOR pathway inhibition with rapamycin
AKT inhibitor reduces mTOR activation and OGN expression in promoting cell death
To explore the possible therapeutic avenues in the
setting of OGN overexpression in meningioma and its
activation of mTOR and AKT, we tested the effect of a small
molecule inhibitor of AKT (AKTVIII) on meningioma
cells. Dose and time titration curves were established to
determine the optimal drug dose for functional analysis
(Fig. 6a). OGN-overexpressing cells demonstrated greater
sensitivity to AKT inhibition, with diminished survival,
compared to control cells at 48 h and 72 h (Fig. 6b).
Protein pathway analysis by Western blot confirmed that
AKT inhibition suppressed AKT activation as well as
downstream mTOR phosphorylation at Ser2448 (Fig. 6c),
the activation of mTOR substrates 4E-BP1, EIF4b, and
eEF2K was also reduced (Additional file 2: Figure S2A).
Interestingly, AKT inhibition also led to a reduction in
OGN expression, suggestive of a reciprocal influence
between OGN and AKT. In addition, NF2 siRNA
significantly reduced NF2 protein expression and activated AKT
while AKT inhibition conversely did not affect NF2
expression in OGN overexpressing cells which indicate
AKT activation is the downstream signal of NF2
(Additional file 2: Figure S2). Addition of AKT inhibitor
reduced the expression of the cell cycle marker cyclin B1,
increased the expression of the autophagy marker LC3IIB,
and suppressed phosphorylation of UNC-51-like kinase
(ULK) at Ser757, a negative regulator in autophagy
activation, supporting a biological cascade leading to the
consequent cell death. The presence of autophagy in
OGN meningioma cells treated with AKT inhibitor was
confirmed by immunoreactivity for LC3IIB (Fig. 6d).
Large scale genomic and epigenomic profiling has
provided new insights into meningioma oncogenesis in
recent years [
]. However, much remains unknown
about the specific signaling cascades leading to tumor
growth. We investigated the effects of OGN, a critical
regulator of bone and cardiovascular development, in
meningioma proliferation, its association with other
known signaling pathways involved in meningioma
development, and explored the treatment options for
OGN-expressing meningioma cells. Although previous
work has identified OGN expression across a range of
cancers, its oncogenic role has not been previously
]. We found that OGN overexpression
increased cell proliferation, that knockdown reduced cell
growth, and that cells expressing high levels of OGN
were sensitive to AKT inhibition; thereby, establishing
for the first time, a potential mitogenic effect for OGN
Our results implicate OGN as an important mitogenic
factor in meningioma growth across a range of tumor
subtypes. Inhibitors of recently identified meningioma
oncogenes, including AKT1, SMO, and PIK3CA, are
now in clinical trial for recurrent and progressive
meningiomas. However, alterations to these pathways
occur in only a small subset of meningiomas, which are
almost exclusively grade I [
]. We observed robust
OGN expression across a wide range of meningioma
histological subtypes and grades, at significantly higher
levels than eight other CNS tumors and normal brain,
posing OGN as an appealing target for those
meningiomas which currently do not have pharmacologic
OGN participates in meningioma formation in a distinct
manner from previously identified genetic alterations.
Genetic mutations and chromosomal aberrations
identified in meningiomas implicate a critical role for cell cycle
promotion, the Hedgehog pathway, and the PI3K/Akt
pathway in tumorigenesis [
]. We observed no
mutation or copy number alterations in OGN in an
extensive series of meningioma samples and cell lines that
underwent next-generation sequencing [
suggests that wildtype OGN may function as a
coactivator of signals that promote meningioma growth and
Interestingly, we identified synergy between OGN and
previously identified oncogenic signaling pathways in
meningioma. OGN appears to downregulate NF2, the
canonical tumor suppressor altered in approximately
half of meningiomas. In addition, meningiomas with
high OGN mRNA levels harbor more frequent NF2 or
chr22 loss than those with low OGN mRNA levels, and
OGN protein expression was higher in meningiomas
with NF2 loss. Furthermore, AKT inhibitors had a
selective effect on cells with high levels of OGN, even in
the absence of oncogenic AKT1 mutations, likely due to
the fact that OGN expression increases p-AKT levels.
Inhibition of AKT did not alter NF2 expression in OGN
cells, while knockdown of NF2 significantly reduced
AKT activation, suggesting that AKT activation could be
the downstream signal of NF2 in OGN overexpressing
cells. The sensitivity of OGN-expressing meningioma
cells to AKT inhibition suggests that OGN expression
may serve as an addition biomarker to stratify the
response of aggressive meningiomas to AKT inhibitors.
We identify OGN as a novel oncogene in meningioma
proliferation. AKT inhibition reduces OGN protein
levels in meningioma cells, with a concomitant increase
in cell death. This study lays a foundation for the
incorporation of OGN expression into personalized treatment
Additional file 1: Figure S1. OGN mRNA expression in tonsil, as a
negative control of OGN RNAscope. (PDF 1195 kb)
Additional file 2: Figure S2. AKT inhibitor reduces mTOR downstream
signaling activation, but without effects on NF2. (A) Addition of AKT
inhibitor (AKTi) to OGN overexpressing cells led to decreased activation
of the mTOR downstream signals 4E-BP1, EIF4b, and eEF2K without
altering NF2 expression. (B) Knockdown of NF2 with siRNA significantly
reduced NF2 protein expression and increased AKT activation in OGN
cells. *p < 0.05. (PDF 1796 kb)
4E-BP1: Eukaryotic translation initiation factor 4E-binding protein 1; AKT: v-akt
murine thymoma viral oncogene homolog; BAP1: BRCA1 Associated Protein
1; COSMIC: Catalogue of somatic mutations in cancer; eEF2K: Eukaryotic
Elongation Factor 2 Kinase; eIF4B: Eukaryotic translation initiation factor 4B;
IHC: Immunohistochemistry; KLF4: Krupplelike factor 4; LC3IIB:
Microtubuleassociated protein light chain 3 IIB; mTORC1: Mammalian target of
rapamycin complex 1; NF2: Neurofibromatosis; OGN: Osteoglycin;
PIK3CA: Phosphoinositide-3-kinase catalytic alpha polypeptide; POLR2A: RNA
polymerase II subunit A; qPCR: Quantitative real-time PCR; SMARCB1: SWI/
SNF related, matrix associated, actin dependent regulator of chromatin,
subfamily b, member 1; SMO: Smoothened; SUFU: Homolog of suppressor of
fused; TERT: Telomerase reverse transcriptase; TRAF7: TNF receptor-associated
factor 7; ULK: UNC-51-like kinase
This work was supported in part by a grant from the Sanad Children’s
Cancer Support Association (MA) and NIH grant K08NS092912 (GPD).
Availability of data and materials
The datasets supporting the conclusions of this article are included within
YM, SS and ID were involved in the study concept and experiment design;
YM conducted all in vitro experiments and analyzed data; YM, ZD and CH
analyzed human tissue data; YM drafted the manuscript; WLB, NG, MA, NA,
GD edited manuscript. All authors read and approved the final manuscript.
Ethics approval and consent to participate
The ethics of this study was approved by the Institutional Review Boards of
Brigham and Women’s Hospital and Dana Farber Cancer Institute, Harvard
Medical School. Consent was obtained from all patients involved in the study.
Consent for publication
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
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