ESTRO 2020 Abstract Book

S249 ESTRO 2020

TRIB1 caused a decrease in apoptosis of PDX cell lines after radiation exposure and TMZ treatment. The overexpression of TRIB1 also increased ERK and Akt signaling in PDX cell lines. It was also observed that TRIB1 levels were upregulated in p53-mutant cell lines. Importantly, TRIB1 knockdown resulted in reduced proliferation of PDX cell lines. Conclusion TRIB1 is a promising therapeutic target for glioma therapy because targeting TRIB1 would promote radio-sensitivity of p53 mutant glioma cells and provide an alternative treatment strategy for MGMT unmethylated patients that do not respond to TMZ. Grant support: National Cancer Institute [R01CA169368 (to A.C.), R01CA11522358 (to A.C.), R01CA1145128 (to A.C.), R01CA108633 (to A.C.), R01CA188228 (to A.C., R.B., K.L., and J.B.), 1RC2CA148190 (to A.C.), and U10CA180850–01 (to A.C.)]; A Brain Tumor Funders Collaborative Grant (to A.C.); Ohio State University Comprehensive Cancer Center Award (to A.C.). OC-0451 Radiation response of breast carcinoma cells with enhanced metastatic capacities B. Aschenbrenner 1 , G. Negro 1 , D. Savic 1 , S.K.B. Kranjc Brezar 2 , M. Cemazar 2 , A.C. Coer 3 , G.G. Gašljević 2 , M.S. Sorokin 4 , A. Buzdin 4 , M.C. Callari 5 , U. .G. Ganswindt 6 , S. Skvortsov 1 , I. Skvortsova 7 1 Medical University of Innsbruck-Tyrolean Cancer Research Institute, EXTRO-Lab- Department of Therapeutic Radiology and Oncology, Innsbruck, Austria ; 2 Institute of Oncology Ljubljana- Ljubljana- Slovenia, Experimental Oncology, Ljubljana, Slovenia ; 3 University of Primorska, Faculty of Health Sciences, Izola, Slovenia ; 4 I.M. Sechenov First Moscow State Medical University, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russian Federation ; 5 University of Cambridge, Cancer Research UK Cambridge Institute, Cambridge, United Kingdom ; 6 Medical University of Innsbruck, Department of Therapeutic Radiology and Oncology, Innsbruck, Austria ; 7 Medical University of Innsbruck- Tyrolean Cancer Research Institute, EXTRO- Lab- Dept. of Therapeutic Radiology and Oncology, Innsbruck, Austria Purpose or Objective Nowadays radiation therapy (RT) plays an important role in the management of early and advanced breast cancer. Although administration of postoperative RT markedly improves disease-free and overall survival in breast cancer patients, the problem of distant recurrence development is still not solved. It is possible to assume that breast carcinoma cells with increased metastatic abilities can possess any specific molecular properties protecting them from ionizing radiation. The main aim of this study was to determine whether breast carcinoma cells with increased invasive capacities are radiation resistant, and which molecular phenotypes can predict a diminished radiation response of invasive breast carcinoma cells. Material and Methods Parental breast carcinoma cells and their invasive counterparts (INV cells) (MDA-MB-231, basal type; T47D, luminal A type; Au565, Her2/ neu -positive cells) were used in the study. INV cells were obtained from parental breast carcinoma cells after repetitive cell migration through the 8µm-pore membrane in the Boyden chamber toward the medium containing an attractant. Cell morphology (3D tomographic microscopy); cell invasion/migration; cell viability and proliferation; expression and activities of

Conclusion Together with our previous results, combining radiation with Notch signalling inhibition improves efficacy of radiation in melanoma by impairing phenotypic plasticity and by attenuating DNA damage response. We further demonstrate this strategy has the potential to reduce metastatic spread in melanoma by impairing cellular migration. Validation of our results using in-vivo models is warranted. OC-0450 TRIBBLES1 (TRIB1) pseudokinase: a potential therapeutic target in GBM K. Singh 1 , J. Fleming 1 , C. Han 1 , T. Cui 1 , B. Johnson 1 , J. Haque 1 , E.H. Bell 1 , P. Robe 2 , A. Chakravarti 1 1 Ohio State University Comprehensive Cancer Center, Radiation Oncology, Columbus, USA ; 2 UMC Utrecht, Neurosurgery, Utrecht, Netherlands Antilles Purpose or Objective GBM (WHO grade IV) is the most aggressive glioma with a 5-year survival rate of 5%. The current therapeutic regimen involves radiation therapy and concurrent and adjuvant TMZ (Stupp protocol). In 2016 WHO classified gliomas on the basis of their IDH 1/2 mutation status such that the IDH1/2 wild type tumors are more aggressive compared to IDH1/2 mutant tumors. In spite of such distribution, both groups are treated similarly by the Stupp protocol. Therefore, there is a need of biomarkers and therapeutic targets to improve the treatment and also provide better patient stratification. In this study, we identified TRIB1, a Ser/Thr pseudokinase that acts as a scaffold protein to cause Ubiquitin Proteasome System mediated degradation of target proteins in the cell. TRIB1 has also been associated with survival of prostate cancer cells and poor disease prognosis. Material and Methods We utilized a patient-centered reverse translational approach to identify novel therapeutic targets. TRIB1 was identified by statistical association (Cox regression analysis) and logic-based network analyses of the patient- derived data. TRIB1 was functionally validated in vitro by overexpression and knockdown studies. For knockdown of TRIB1, doxycycline inducible system was used. Stable cell lines were created by puromycin selection and cell sorting. Protein levels were detected by western blotting. Results The global methylation analysis on Utrecht GBM cohort revealed that levels of Trib1 promoter methylation is associated with better OS of GBM patients. The TRIB1 promoter was also shown to be less methylated in MGMT unmethylated tumors. We also observed that TRIB1 was induced after radiation exposure. The overexpression of