Abstract Book

S1255

ESTRO 37

EP-2273 Chondrogenic differentiation in vitro results in DDR activation in induced pluripotent stem cells E. Stelcer 1,2,3 , K. Kulcenty 1,2 , M. Ruciński 4 , K. Jopek 4 , T. Trzeciak 5 , M. Richter 5 , W.M. Suchorska 1,2 1 Greater Poland Cancer Centre, Radiobiology Lab, Poznan, Poland 2 Poznan University of Medical Sciences, Department of Electroradiology, Poznan, Poland 3 Medical University of Warsaw, The Postgraduate School of Molecular Medicine, Poznan, Poland 4 Poznan University of Medical Sciences, Department of Histology and Embryology, Poznan, Poland 5 Poznan University of Medical Sciences, Department of Orthopedics and Traumatology, Poznan, Poland Purpose or Objective Previously, we investigated the mechanisms of DDR activated in chondrocyte-like cells differentiated from human induced pluripotent stem cells (ChiPS) after IR treatment. Importantly, irradiated ChiPS reveal the extremely high level of DNA repair mechanisms. In our judgment, a such high level of DDR mechanisms is considerably associated with the forced chondrogenic differentiation in vitro, that constitutes a meaningful stress for cells. Hence, in this study we focused on inducing DDR mechanisms in ChiPS acquired during differentiation in vitro. The aims of the study were: a) to investigate gene expression profile of the obtained ChiPS, b) to compare expression of genes involved in DDR process between ChiPS with hiPSCs and mature chondrocytes c) to evaluate the level of activated stress leading to DNA damage in hiPSCs undergoing

amounts of apoptosis in all cell lines. Cy143BMELAS 2.0Gy increased damage in Cy143Bwt but it did not induce an increase in apoptosis. The response of cells to conditioned media was also different, for Cy143BMELAS showed little response to conditioned media from Cy143Bwt. No effect was observed when 143B- ρ0 conditioned media was used. Conclusion These results point to a possible role of mitochondria in the radiation-induced bystander effect which upon better characterization, may be an interesting modulator of the response to Radiotherapy. EP-2272 Liver stereotactic body radiation therapy modulates systemic pharmacokinetics of sorafenib C.H. Hsieh 1 , T.H. Tsai 2 , Y.J. Chen 3 , L.Y. Wang 4 1 Far Eastern Memorial Hospital, Radiation Oncology, Taipei, Taiwan 2 National Yang-Ming University, Institute of Traditional Medicine, Taipei, Taiwan 3 Mackay Memorial Hospital, Departments of Radiation Oncology, Taipei, Taiwan 4 National Taiwan University, School and Graduate Institute of Physical Therapy, Taipei, Taiwan Purpose or Objective Sorafenib is a multi-kinase inhibitor that demonstrated a significant improved survival of patients with hepatocellular carcinoma (HCC). The efficacy of stereotactic body radiation therapy ( SBRT ) concurrent or sequential with sorafenib in unresectable HCC patients has better effects than single agent. However, the effects of local SBRT on sorafenib in the plasma system remain unclear. Here, we evaluate the influence of liver SBRT on the pharmacokinetics (PK) of sorafenib using rats as an experimental model. Material and Methods Free-moving Sprague-Dawley rat model was used in the current study. Image-guided SBRT with 9 Gy was delivered to the liver by 1.5 x 1,5 cm. The experimental animals were randomized to the sham RT (0 Gy with sorafnib), concurrent and sequential group, respectively. The concurrent group was feeding with sorafenib (40 mg/kg) after SBRT-treated1 hour and sequential model was feeding with post SBRT-treated 24 hours. The PK of sorafenib in the plasma system was calculated. Each group’s data was collected from six rats Results Compared to the sham-irradiated controls, the area under the concentration versus time curve (AUC) of sorafenib (40 mg/kg) was increased 263% in concurrent group (720 versus 1891 min*ug/mL, p = 0.038). Additionally, the AUC of sorafenib was increased by 202% in sequential group (720 versus 1457 min*ug/mL, p = 0.018). There was no statistically significant difference of AUC between both groups. Compared to the control group, the Cmax was increased 279% and 198% for concurrent and sequential group, respectively. There were no differences at Tmax between groups. Conclusion Liver SBRT modulates the systemic PK of sorafenib of the rats. Interestingly, the AUC of sorafenib is increased no matter concurrent or sequential model. The SBRT-PK phenomena are not only noted in chemotherapy agents but also in target therapy drug. The clinical application of RT-PK phenomena is warranted.

differentiation in vitro. Material and Methods •

Chondrogenic differentiation of hiPSCs (Suchorska et al., 2017) was conducted. Global gene expression microarray was performed and analyzed using GeneAtlas TM WT Expression Kit Assay and AffymetrixGeneAtlasTM Operating Software. The Bioconductor and statistical programming language R were used. Set of differentially expressed genes were subjected to functional annotation and clusterization using DAVID web-based bioinformatics tools. Gene symbols for differentially expressed genes were uploaded to DAVID by 'RDAVIDWebService” BioConductor library, where selection of significantly enriched ontological terms related to regulation of DDR mechanisms was performed. The validation of microarrayswas performed by RT-qPCR.

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Results All differentially genes engaged in specific biological processes were visualized using Gene Ontology (GO) plot library. Our latest results indicate that ChiPS possess induced DDR mechanisms acquired during differentiation. In ChiPS, the increased expression of genes classified to the following GO terms: 'signal transduction in response to DNA damage”, 'mitotic DNA damage checkpoint”, 'G1 DNA damage checkpoint”, and "intracellular signal transduction involved in G1 DNA damage checkpoint" is observed. Moreover, based on the Kyoto Encyclopedia of Genes and Genomes the one of superior pathway regulated during chondrogenic differentiation in vitro is p53. The expression of selected genes: CDK1, CDK2, PMAIP1, RGCC, UBC, BTG2 involved in DDR mechanisms and especially in p53 signaling pathway was verified with