ESTRO 36 Abstract Book

68 / 1082

S55 ESTRO 36 2017
_______________________________________________________________________________________________
A. Rühle1, R. Lopez Perez1, K.J. Weber2, J. Debus1,2, P.E.
Huber 1,2, N.H. Nicolay1,2
1 German Cancer Research Center, Radiation Oncology,
Heidelberg, Germany
2 University Hospital, Radiation Oncology, Heidelberg,
Germany
Purpose or Objective
Mesenchymal stem cells (MSCs) have been shown to aid
the regeneration of tissue damage induced by ionizing
radiation or cisplatin. While these stem cells are relatively
resistant to photon irradiation and cisplatin treatment
alone, the influence of clinically relevant cisplatin-based
chemo-radiation regimes on the survival and functional
abilities of MSCs is unknown.
Material and Methods
The survival of human bone marrow-derived MSCs was
assessed after pre-treatment with different doses of
cisplatin, and the influence of cisplatin chemo-radiation
on cellular morphology, adhesion and migratory abilities
and differentiation potential was analyzed. Cell cycle
distribution and apoptosis levels of MSCs were measured
using flow cytometry, and DNA double strand break repair
capacities were evaluated by immunofluorescence.
Results
Cisplatin pre-treatment resulted in a dose-dependent
radiosensitization with sensitizer enhancement ratio
values ranging between 1.07 and 1.30 depending on the
cisplatin treatment dose. Cellular morphology, adhesion
and migratory abilities were not significantly influenced
by cisplatin chemo-radiation. MSC differentiation
capability along the adipogenic and chondrogenic lineages
was preserved after chemo-radiation, and the defining
stem cell surface markers were stably expressed
irrespective of treatment. Cisplatin pre-treatment
resulted in an accumulation of MSCs in the radiosensitive
G2/M phase of the cell cycle. Immunofluorescence
analyses showed an increase in both initial and residual
radiation-induced DNA double strand breaks following pre-
treatment with cisplatin.
Conclusion
We could demonstrate for the first time that pre-
treatment with cisplatin resulted in a dose-dependent
sensitization of radioresistant MSCs, whereas the defining
stem cell characteristics of the stem cells were largely
preserved. A cisplatin-mediated G2/M phase arrest and an
increase in residual radiation-induced DNA double strand
breaks may at least be partly responsible for the
radiosensitizing effect of cisplatin in MSCs.
OC-0118 Mesenchymal stem cells are resistant to
ionizing radiation irrespective of their tissue of origin
N.H. Nicolay1,2, A. Rühle2, O. Xia2, R. Lopez Perez 2, J.
Debus 1,2, P.E. Huber1,2
1 University Hospital, Radiation Oncology, Heidelberg,
Germany
2 German Cancer Research Center, Radiation Oncology,
Heidelberg, Germany
Purpose or Objective
Mesenchymal stem cell-based therapies may provide a
novel approach to treat radiation-induced organ damage.
While mesenchymal stem cells (MSCs) required for those
potential treatments can be harvested from various
different tissues, the influence of ionizing radiation on the
stem cells from diverse original tissues themselves is
largely unknown.
Material and Methods
The radiation response of MSCs isolated from human bone
marrow, adipose tissue and umbilical cord was
investigated. Cellular survival, cell cycle effects and
apoptosis were measured and compared to that of
differentiated fibroblasts. The influence of irradiation on
the defining stem cell properties was assessed, and the
radiation effects on MSC morphology, surface marker
expression, adhesion and migration capabilities and the
differentiation potential were measured.
Immunocytochemical analyses of DNA damage and repair
foci were carried out to quantify the MSCs' ability for DNA
double strand break repair.
Results
MSCs from different tissues were found to exhibit a
relative radiation resistance comparable to that of
differentiated fibroblasts. Irradiated MSCs demonstrated a
prolonged arrest in G2 phase of the cell cycle, but were
able to avoid induction of apoptosis even after treatment
with high radiation doses. Surface marker expression,
stem cell adhesion and migration capability were not
generally reduced by irradiation, and MSCs also
maintained their potential for adipogenic, osteogenic and
chondrogenic differentiation. Analysis of DNA
damage/repair foci demonstrated a swift and efficient
repair of radiation-induced DNA double strand breaks in
MSCs, providing an explanation for the observed radiation
resistance of these stem cells.
Conclusion
These data demonstrate for the first time that MSCs from
diverse human tissues exhibit comparable resistance to
ionizing radiation and also largely maintain their defining
stem cell characteristics independent of their original
tissue. The observed radiation resistance of MSCs from
different tissues will help to establish diverse stem cell
sources for future MSC-based therapies against radiation-
induced organ damage.
OC-0119 Dermatan sulfate mitigates radiation-induced
oral mucositis (mouse) – biological mechanisms
S. Gruber1, E. Bozsaky1, M. Arnold1, S. Pfaffinger1, S.
Hetzendorfer1, V. Gernedl1, A. Rohorzka1, L. Kowald1, S.
Morava1, J. Mayer1, P. Kuess1, W. Dörr 1
1Medizinische Universität Wien Medical University of
Vienna, Univ.Klinik f. Strahlentherapie, Vienna, Austria
Purpose or Objective Oral mucositis is the most frequent,
dose limiting early adverse event of head-and-neck cancer
radio(chemo)therapy. The present study quantified the
mucoprotective effect of dermatan sulfate (DS) and
characterised the underlying biological mechanisms.
Irradiation- and DS-mediated changes of epithelial
proliferation, cell junction formation, inflammation and
hypoxia were investigated.
Material and Methods
The study comprises functional and mechanistic
investigations. For the functional assessment of mucosal
ulcer incidence and time course, mice were irradiated
with 5x3 Gy/week over one (days 0-4) or two weeks (days
0-4, 7-11). Each protocol was concluded by graded top-up
doses (day 7/14) to generate complete dose-effect curves.
Daily doses of DS (4 mg/kg subcutaneously) were applied
over varying time intervals during either the first or the
second week of fractionation alone, or during both weeks,
respectively. In the mechanistic analyses, groups of five
mice per experimental arm were sacrificed every second
day during the two week fractionated irradiation, the
tongues were excised and subjected to histological /
immunohistochemical processing.
Results
DS significantly increased the isoeffective doses for the
induction of oral mucositis in almost all protocols. DS
furthermore prolonged the latency to epithelial ulceration
and reduced ulcer duration. Proliferation measurements
did not show any substantial or systematical effect of DS.
In contrast, the radiation-induced increase in the
expression of the adherens junction proteins e-cadherin
and β-catenin as well as the tight junction proteins claudin
and occludin occurred significantly earlier and more
pronounced with additional DS treatment. The expression
of IL-1β and NF-κB as markers of inflammation was
dramatically increased during irradiation alone; while DS
treatment significantly inhibited the radiation-induced