Poster 148
IDENTIFICATION OF SIGNALING CHANGES AND
POTENTIAL COMBINATION THERAPIES WITH MDM2
INHIBITION IN DEDIFFERENTIATED LIPOSARCOMA
CELLS
Jeannine Garnett, PhD1; Kate Lynn Bill, BS2; Shen Li3;
Chad J. Creighton4; Peng Qiu3; Davis Ingram, BS2;
Ghadah A. Al Sannaa2; Svetlana Bolshakov1;
XiaoYan Ma1; Christine M. Kivlin, BS Biology1;
Caitlin May1; Raphael E. Pollock1; Dina C. Lev1;
Keila E. Torres, MD, PhD1; Alexander J. Lazar, MD, PhD2
1Surgical Oncology, The
University of Texas MD
AndersonCancerCenter,
Houston, TX, USA;
2Pathology, The
University of Texas MD
AndersonCancerCenter,
Houston, TX, USA;
3Bioinformatics and
Computational Biology,
The University of Texas
MD Anderson Cancer
Center, Houston, TX,
USA; 4Department of
Medicine, BaylorCollege
of Medicine, Houston,
TX, USA
Objective: Dedifferentiated
liposarcomas (DDLPS) are
aggressive tumors with
poor patient outcome.
DDLPS is characterized by conspicuous punctuated
12q13~22 amplification, resulting in overexpression of
MDM2. MDM2 ubiquitinates the tumor suppressor protein
p53 leading to its degradation, and sterically hinders its
activation at N-terminal phosphorylation sites. Currently,
MDM2 inhibitors are being evaluated for the treatment of
soft tissue sarcomas in early-phase clinical trials. Since
MDM2 inhibition enhances p53 activity in DDLPS, goals
of these studies included unraveling signaling changes
associated with an MDM2-p53 competitive inhibitor over
time in DDLPS cells, and identification of synergistic cotargetable
nodes.
Methods: A targeted reverse phase protein array captured
signaling changes of 4 DDLPS cell lines treated
with DMSO or an MDM2 inhibitor, Nutlin-3A, at 8 and 24
hrs. Significance was calculated using modified paired
two-sample t-tests (P <0.05), followed by controlling for
false discovery rates using the beta-uniform mixture model
(FDRs <0.05). Statistically significant protein changes were
evaluated using Ingenuity Pathway Analysis (IPA) at 8 and
24 hr timepoints. Western blot validations are ongoing, and
upregulated oncogenic signaling nodes will be co-targeted
and evaluated using proliferation assays.
Results: After DDLPS cells were treated with Nutlin-3A for
8 hrs, 28 proteins significantly changed in their expression
or activation status, and at 24 hrs 67 proteins were altered.
Fold changes of significant total proteins entered into IPA
revealed that the top signaling network affected was cell
death and survival. Interestingly this network was not predicted
to be regulated by p53 at 8 hrs, but strong pathway
interconnections suggested that it was p-53-modulated
at 24 hrs. Additionally, potential combination therapeutic
strategies have been identified.
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Conclusion: A broader understanding of signaling changes
and potential nodes of DDLPS therapeutic vulnerability
is critical for the effective use of MDM2 inhibitors in the
clinical setting.