ESTRO 37 Abstract book

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ESTRO 37

necessary. This study aimed for the synthesis of a novel DNA-methyltransferase inhibitor (DNMTi) that radiosensitize glioblastoma cells and possess biostability. Material and Methods A novel non-nucleoside heterodimer, designated as compound MA17, was derived from RG108 which is a commercially available DNMTi. Three human GBM cell lines (U373MG, U87MG, and T98G) and normal human astrocytes (NHAs) were screened for the radiosensitizing effects of MA17. Clonogenic assays were performed in triplets to measure cell lethality, and sensitizer enhancement ratios (SERs) at survival fraction of 0.5 were obtained to quantify the radiosensitizing effect of MA17 in each cell line. Quantitative assays of DNMT1 inhibition was performed. Pharmacokinetic character- ristics were examined in mice (n=4) at a concentration of 10 mg/kg. Results MA17 significantly radiosensitized U373MG, U87MG, and T98G with mean SERs of 1.896, 1.312, and 1.331, respectively (all p <0.05 by ratio paired t-test) (Fig. 1). However, MA17 did not affect the radiation lethality in NHAs with mean SER of 0.960 (95% confidence interval, 0.897–1.023; p =0.193). MA17 also inhibited the activity of DNMT1 by 60.29±28.22%. The mean half-life of MA17 in vivo was 1.0±0.2 hour. Conclusion A novel DNMTi, MA17, significantly enhances cell lethality of radiation in GBM cells without affecting the radiation response in NHAs. Biostability of MA17 was also proven with a long half-life in vivo . In vivo studies for MA17 using a xenograft mouse model are ongoing. EP-2315 Tumor IGF-1 and insulin receptor expression and its linkage to anti-receptor treatment response A. Iversen 1 , M. Vendelbo 2 , N. Jessen 3 , J. Frøkiær 4 , A. Morsing 5 , M. Busk 1 1 Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus C, Denmark 2 Aarhus University Hospital, Department of Nuclear Medicine and PET Center, Aarhus C, Denmark 3 Aarhus University, Department of Clinical Medicine, Aarhus, Denmark 4 Aarhus University Hospital, Department of Nuclear Medicine and PET-Center, Aarhus C, Denmark 5 Aarhus University Hospital, Department of Nuclear Medicine and PET Centre, Aarhus C, Denmark Purpose or Objective IGF-1 and Insulin receptors (IGF-1R and IR) are increased in various cancers. Receptor stimulation leads to enhanced glucose consumption and protein synthesis and thus tumor growth through the Akt/mTOR pathway. Increased expression of IGF-1R has been linked to radioresistance, and IGF-1R is an emerging target in radiotherapy. The IGF-1R and IR inhibitor OSI-906 has shown promising results and is undergoing clinical testing. We set out to investigate if IGF-1R and IR inhibition is associated to decreased Akt/mTOR activation and glucose uptake in cancer cells, and to develop a PET detectable probe for IGF-1R and IR based on chemical OSI-906 was used to detect Insulin and IGF-1 sensitive cancer cells. Effect of inhibition was assessed with 18 F- FDG uptake, measurements of glycolysis and phosphorylations on Akt and mTOR in stimulated and non- stimulated conditions. Furthermore, we are currently modification of OSI-906. Material and Methods

assessing the specificity of [11C]-methyl-OSI-906 in tissue samples. Results Metabolic in vitro assays based on 18 F-FDG and extracellular flux analysis revealed that both insulin and IGF stimulated glucose uptake and lactic acid formation in most cell lines. These changes were effectively inhibited by OSI-906. The most pronounced effect was detected in SW948 colon cancer cells and in accordance with metabolic data, Akt and mTOR phosphorylation could be stimulated by IGF-1 and insulin, and this stimulation was effectively inhibited by OSI-906. Non- radioactive methyl-OSI-906 (backbone for the PET tracer) was able to block receptor stimulation and we are currently assessing the specificity of [11C]-methyl-OSI- 906. Conclusion Present results demonstrate that IGF-1R and IR inhibition reduce Akt/mTOR signaling, glycolysis and 18 F-FDG uptake in SW948 cells. Furthermore, [11C]-methyl-OSI-906 may detect cells responsive to IGF-1R and IR inhibition monotherapy or combination therapy with radiotherapy, which could allow for rational individualized therapy. EP-2316 Inhibiting ephrin reverts oncophenotype and radiosensitizes embryonal rhabdomyosarcoma cells. F. Marampon 1 , G.L. Gravina 1 , C. Festuccia 1 , F. De Felice 2 , D. Musio 2 , V. Tombolini 2 1 University of L'Aquila, of Biotechnological and Applied Clinical Sciences- Division of Radiation Oncology- University of L'Aquila- L'Aquila- Italy., L'Aquila, Italy 2 Unversity of Rome- Sapienza, of Radiological- Oncological and Pathological Sciences, Rome, Italy Purpose or Objective EPH (erythropoietin-producing hepatocellular) receptors are clinically relevant targets in several malignancies. This report describes the effects of GLPG1790, a new potent pan-EPH inhibitor, in human embryonal rhabdomyosarcoma (ERMS) cell lines. Material and Methods EPH-A2 and Ephrin-A1 mRNA expression was quantified by real-time PCR in 14 ERMS tumour samples and in normal skeletal muscle (NSM). GLPG1790 effects were tested in RD and TE671 cell lines, two in vitro models of ERMS, by performing flow cytometry analysis, Western blotting and immunofluorescence experiments. RNA interfering experiments were performed to assess the role of specific EPH receptors. Radiations were delivered using an x-6 MV photon linear accelerator. GLPG1790 (30 mg/kg) in vivo activity alone or in combination with irradiation (2 Gy) was determined in murine xenografts. Results Our study showed, for the first time, a significant upregulation of EPH-A2 receptor and Ephrin-A1 ligand in ERMS primary biopsies in comparison to NSM. GLPG1790 in vitro induced G1-growth arrest as demonstrated by Rb, Cyclin A and Cyclin B1 decrease, as well as by p21 and p27 increment. GLPG1790 reduced migratory capacity and clonogenic potential of ERMS cells, prevented rhabdosphere formation and downregulated CD133, CXCR4 and Nanog stem cell markers. Drug treatment committed ERMS cells towards skeletal muscle differentiation by inducing a myogenic-like phenotype and increasing MYOD1, Myogenin and MyHC levels. Furthermore, GLPG1790 significantly radiosensitized ERMS cells by impairing the DNA double-strand break repair pathway. Silencing of both EPH-A2 and EPH-B2,