ESTRO 36 Abstract Book

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S543 ESTRO 36
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effectively induced ubiquitination and degradation of
Nrf2, and inhibited translocation of Nrf2 to the nucleus.
Consequently, expression of Nrf2 downstream genes was
reduced, and the Nrf2-dependent antioxidant system was
suppressed. Endogenous ROS was higher than before ISL
treatment, causing redox imbalance and oxidative stress
in HepG2 cells. Moreover, pretreatment with ISL for 6 h
followed by X-ray irradiation significantly increased γ-
H2AX foci and cell apoptosis, and reduced clonogenic
potential compared with cells irradiated with X-rays
alone. In addition, HepG2 xenografts, ISL, and X-ray
cotreatments induced greater apoptosis and tumor growth
inhibition, when compared with X-ray treatments alone.
Additionally, HepG2 xenografts, in which Nrf2 was
expressed at very low levels due to ectopic expression of
Keap1, showed that ISL-mediated radiosensitization was
Keap1 dependent.
Conclusion
ISL inhibited the Nrf2-antioxidant pathway by increasing
the levels of Keap1 and ultimately inducing oxidative
stress via disturbance of the redox status. The antioxidant
ISL possessed pro-oxidative properties, and enhanced the
radiosensitivity of liver cancer cells, both in vivo and in
vitro . Taken together, these results demonstrated the
effectiveness of using ISL to decrease radioresistance,
suggesting that ISL could be developed as an adjuvant
radiosensitization drug. Disturbance of redox status could
be a potential target for radiosensitization.
PO-0982 Fused Toes Homolog (FTS) is a potential
target for Notch-mediated radioresistance in cervical
cancer
W.Y. Park1, P.D. Subramania1, J.R. Yu2
1 Chungbuk National University Hospital, Dept of
Radiation Oncology, Cheongju, Korea Republic of
2 Konkuk University, Department of Environmental and
Tropical Medicine, Chungju, Korea Republic of
Purpose or Objective
Radiation therapy is one of the major treatment
modalities for cervical cancer. Increasing evidences
suggest that cancer stem cells (CSC) in tumours contribute
to radioresistance and recurrence. Notch pathway plays a
vital role in maintenance of cancer stemness and its
activation leads to disease progression and metastasis. FTS
gene was initially identified as one of six genes deleted in
a mouse mutant called Fused Toes, due to defects in limb
development, and referred as FT1/FTS. However, the
function of FTS has not been elucidated well in human. We
previously reported that FTS plays an essential role in
nuclear phosphorylation of EGFR and repair of DNA
damage, and epithelial-mesenchymal transition. In this
study, we evaluated the role of FTS in Notch signaling and
CSCs.
Material and Methods
A human cervical cancer cell line (ME180) was used.
Silencing of FTS was obtained using siRNA. Western blot
and immunofluorescence was done to analyze the
expression and localization of the proteins.
Results
Protein expression of Notch 1, cleaved Notch1, Notch 3,
γ-secretase complex and its downstream Hes-1was
increased by ionizing radiation and it was reduced by FTS-
silencing. Spheroid formation ability and cancer stem cell
markers Nanog, Oct-4A, Sox2 were reduced by FTS-
silencing. Cell survival was decreased by FTS-silencing.
Conclusion
FTS is involved in the regulation of Notch signaling and CSC
maintenance. FTS can be a target to overcome Notch–
mediated radioresistance in cervical cancer.
PO-0983 Antrodia cinnamomea Regulates DNA Repair
and Enhances Radiosensitivity of Esophageal Cancer
Cells
Y.M. Liu1, Y.J. Chen2, Y.K. Liu3, T.H. Tsai4
1Taipei Veteran General Hospital, Div. of Radiation
Oncology- Dept. of Oncology, Taipei, Taiwan
2MacKay Memorial Hospital, Department of Radiation
Oncology, New Taipei City, Taiwan
3Chang Gung University, Department of Chemical and
Material Engineering, Taoyuan City, Taiwan
4National Yang Ming University, Institute of Traditional
Medicine, Taipei, Taiwan
Purpose or Objective
This study investigated the adjunctive effects of Antrodia
cinnamomea mycelial fermentation broth (AC-MFB), a
Taiwanese medicinal fungus, in enhancing the
radiosensitivity of esophageal cancer cells. in vitro and in
vivo.
Material and Methods
Materials: Antrodia cinnamomea mycelial fermentation
broth, Human CE81T/VGH squamous and BE3
adenocarcinoma esophageal cancer cells, BALB/c mice.
Method: MTT assay, colony formation assay, DNA
histogram study, γ-H2AX immunofluorescence assay,
Western blotting assay, BALB/c mice animal model study.
Results
A colony formation assay showed that pretreatment with
AC-MFB decreased the survival of irradiated esophageal
cancer cells, with a maximum sensitizer enhancement
ratio of 1.91 and 37% survival. A DNA histogram study
showed that AC-MFB pretreatment enhanced cell cycle
arrest at the G2/M phase, the most radiosensitive phase.
An immunofluorescence assay and a Western blotting
assay showed that AC -MFB delayed the abrogation of γ-
H2AX, upregulated p21 expression, and attenuated the
radiation-induced phosphorylation of ataxia
telangiectasia-mutated kinase and checkpoint kinase 2. An
in vivo validation study showed that AC -MFB treatment
tended to have a synergistic effect with radiation on the
tumor growth delay of CE81T/VGH cells in BALB/c mice.
Conclusion
These data suggest that this edible fungus product could
enhance the effect of radiotherapy against esophageal
cancer.
PO-0984 Checkpoint HLA-G or its ligands ILT2/ILT4
changes radiosensitivity of renal carcinoma cell lines
C. Hennequin1, M. Daouya1, D. Tronik-Le Roux1, J.
LeMaoult1, N. Rouas-Freiss1, F. Desgrandchamps1, E.
Carosella 1
1Hôpital Saint-Louis, Research in Immuno-hematology,
Paris, France
Purpose or Objective
HLA-G is an immune checkpoint physiologically implicated
in maternal-foetal tolerance. It is also neoexpressed in
many cancers and particularly in more than 50% of renal
cancers. Stereotactic radiotherapy efficiency is at least in
part mediated by the immune system, and could be
modulated by the presence of immune checkpoints; for
example the use of antibodies directed against PD1/PDL1
increased radiotherapy efficiency. We investigated the
impact of expression of HLA-G or its ligands (ILT2/ILT4) on
radiotherapy efficiency at the cellular level on renal
carcinoma cell lines (RCCL).
Material and Methods
The effect of ionizing radiations (IR: 8 Gy) on the
expression of HLA-G, ILT2 and ILT4 was evaluated on RCCL
expressing or not HLA-G, ILT2 or ILT4. The impact of HLA-
G, ILT or ILT4 expression on radiosensitivity was evaluated
by clonogenic assays on transduced RCCL or controls. In
order to explain the results obtained, the following
mechanisms were investigated by cytofluorimetry: 1/
quantification of double-strand breaks (H2AX) 2/