ESTRO 36 Abstract Book

S544 ESTRO 36 _______________________________________________________________________________________________

apoptosis (Annexin V and propidium iodin PI) 3/ Cell cycle modifications (PI) Results Our results showed that IR on RCCL not expressing HLA-G, ILT2 or ILT4 did not induce these molecules. However, in constitutively expressing HLA-G or ILT4 RCCL, IR decreased significantly HLA-G and ILT4 expression. Furthermore, we found that HLA-G, ILT2 and ILT4 transduction increased radioresistance. This effect was partially aborted by the use of antibodies directed against these molecules. Mechanisms of radio resistance are under investigations and will be presented at the meeting. Conclusion Ionizing radiation decreases the expression of HLA-G or its receptors in RCCL constitutively expressing these molecules. HLA-G and its ligands increase radioresistance. This finding could have some clinical implications for stereotactic radiotherapy of renal cancer or its metastasis. PO-0985 Tumor metabolic changes after neoadjuvant radiotherapy: consequences for surgery-related metastases N. Leroi 1 , F. Lallemand 2 , J. Leenders 3 , S. Blacher 4 , P. De Tullio 3 , P. Coucke 5 , A. Noel 4 , P. Martinive 1 1 C.H.U. Liège - Université de Liège, Radiotherapy Dept- Laboratoire de Biologie des Tumeurs et du Développement, Liège, Belgium 2 C.H.U. Liège - Université de Liège, Radiotherapy Dept- Research center of Cyclotron, Liège, Belgium 3 Université de Liège, CIRM- Chimie Pharmaceutique, Liège, Belgium 4 Université de Liège, Laboratoire de Biologie des Tumeurs et du Développement, Liège, Belgium 5 C.H.U. Liège - Université de Liège, Radiotherapy Dept., Liège, Belgium Purpose or Objective Neoadjuvant radiotherapy (NeoRT) aims at improving tumor local control and patient overall survival. In the case of locally advanced rectal cancer, NeoRT increases significantly local control compared to surgery alone, but patient overall survival is not improved. Currently, predicting tumor response and recurrences represent a major challenge for personalized medicine. Previously, we developed a pre-clinical model of NeoRT and showed that the timing of surgery and NeoRT schedules both influenced metastasis burden (Leroi et al., Oncotarget, 2015). Based on this model, we study the impact of RT schedule on the primary tumor metabolome at the time of surgery to predict local recurrence and metastatic profile. Material and Methods We locally irradiated primary tumors (MDA-MB231 cells and 4T1 cells), subcutaneously implanted to SCID and BalbC mice, with two NeoRT schedules (5x2Gy and 2x5Gy). We surgically removed tumors 4 or 11 days after the end of RT and kept the mice alive for the metastatic growth. Non-irradiated control tumors were also surgically collected at the same time. For metabolomic study, tumor samples were homogenized in deuterated phosphate buffer and supplemented with maleic acid and TMSP before Nuclear Magnetic Resonance (NMR) analyses. Data were analyzed with powerful statistical tool (supervised and multivariate analyses). Results Irradiated 4T1 and MDA-MB231 tumors displayed different metabolic profile than non-irradiated tumors, especially 4 days after the end of RT for 4T1 tumors and 11 days after NeoRT for MDA-MB231 tumors. Moreover, we observed a decrease in some metabolite levels (i.e. glutamate, taurine, glycine, myoinositol) in tumors following both NeoRT schedules. We also noticed an increase in general lipid signals in irradiated MDA-MB231 tumors. This was not related to adipocyte infiltration, as we observed, by immunostaining, decreased infiltration of perilipin and

FABP4+ cells in these tumors following NeoRT. Preliminary results with OPLS-DA analyses showed discrimination of primary tumor metabolome according to the propensity to induce loco-regional recurrence (significant for tumors collected 4 days after 5x2Gy). Furthermore, based on the metabolic profile of the primary MDA-MB231 tumors and OPLS linear regression, mathematical models were established in the different groups allowing to predict the metastatic burden (r²=0,80-0,90). Conclusion In preclinical models, we show profound modifications of the primary tumor metabolome following NeoRT through NMR analyses, offering new opportunities to understand tumor metabolism adaptation following NeoRT. Furthermore, others NMR results appear very relevant when transposed to clinic. Indeed, with mathematical models, local recurrence and metastatic profiles were predictable based on the metabolomic profile of the primary tumor at the time of surgery, which could be helpful to adapt adjuvant therapies in order to prevent relapse. PO-0986 Downregulation of the oncoprotein SET enhances RT-induced apoptosis in hepatocellular carcinoma C.Y. Huang 1 , M.H. Hung 2 , C.W. Kuo 3 , C.T. Shih 4 , M.H. Chen 4 , K.F. Chen 5 1 National Taiwan university hospital, Division of Radiation Oncology- Department of Oncology, Taipei, Taiwan 2 Taipei Veterans General Hospital, Division of Medical Oncology- Department of Oncology, Taipei, Taiwan 3 Yuanpei University of Medical Technology, Department of Medical Imaging and Radiological Technology, Hsinchu, Taiwan 4 National Yang-Ming University, Institute of Biopharmaceutical Sciences, Taipei, Taiwan 5 National Taiwan university hospital, Department of Medical Research, Taipei, Taiwan Purpose or Objective Hepatocellular carcinoma (HCC) is among the most lethal human malignancies worldwide. Radiotherapy (RT) is not commonly used to treat HCC with regard to both suboptimal treatment efficacy and toxicity. The current project aimed to characterize the role of a novel oncoprotein SET/ I2PP2A (Inhibitor-2 of protein phosphatase 2A) in mediating the radio-resistance of HCC cell and explore the potential on antagonizing SET to improve the anti-HCC effects of RT. Material and Methods The effects of RT in HCC cells with different expression of SET were assessed by colony formation and sphere formation assay. We generated a novel SET antagonist, EMQA (N 4 -(3-ethynylphenyl)-6,7-dimethoxy-N 2 -(4- phenoxyphenyl) quinazoline-2,4-diamine), to validate the therapeutic potential of targeting SET. The combination effects of EMQA and RT were tested in vitro using four different HCC cell lines, Hep3B, PLC5, HA22T and HA59T, and a subcutaneous PLC5 xenografted model in vivo. HCC cells were exposed to 1 fraction of 4-Gy radiation using a cobalt 60 unit (at a dose rate of 0.5 Gy/min) with the source-axis-distance set at 80 cm to the bottom of the dish. After 48 hours, the cells were treated with or without EMQA. Results To explore the roles of SET in affecting the radio- sensitivity in HCC, we first generated PLC5 and Hep3B cells with different SET activity, and assessed the effects of RT on these cells by colony formation and tumor sphere assay. Comparing to mock-treated cells, HCC cells transfected with shRNA against SET were shown with significant reduced viability under the same RT treatment. Oppositely, cells with ectopic expression of SET were more resistant to RT. Next, we used EMQA to test whether