Abstract book - ESTRO meets Asia

S125 ESTRO meets Asia 2018

assembly transcript 1 (NEAT1) is a lncRNA which has been demonstrated to be required for the development of murine mammary gland and lactation. Material and Methods (1)To compare NEAT1 expression profiles between radioresistant TNBC cells and the parental counterparts (2) To determine the role of NEAT1 in the self-renewal and radiosensitivity of TNBC CSCs. (3). To analyze the expression of stemness or DNA damage response genes in NEAT1 knockdown or overexpression TNBC CSCs. Results (1)Two TNBC cell lines, MDA-MB-231 and AS-B244, received radiation exposure and showed a radioresistant phenotype by analyzing the survival fractio. The CSC activity in radioresistant TNBC cells and their parental counterparts was compared with mammosphere cultivation. These data suggests that CSCs were enriched in radioresistant TNBC cells. (2)We next extracted the total RNA from TNBC cells and their radioresistant sublines and used quantitative RT-PCR to analyze the expression of NEAT1 between them. NEAT1 was upregulated in radioresistant TNBC cells. We further prepared RNA samples from mammospheres derived from TNBC cells and compared the expression of MALAT1 and NEAT1 with their parental cells. The quantitative RT-PCR data revealed that MALAT1 and NEAT1 was upregulated in mammospheres. (3) Knockdown of MALAT1 or NEAT1 inhibits cell proliferation, mammosphere formation and cell invasion of radioresistant TNBC cells We next used antisense oligo (ASO) to knockdown MALAT1 or NEAT1 expression in TNBC cells and the radioresistant sub-lines and observed the cell growth. That knockdown of MALAT1 or NEAT1 caused growth inhibition in both radioresistant TNBC cells and their parental cells. By mammosphere cultivation and ASO transfection, knockdown of MALAT1 or NEAT1 decreased mammosphere formation in radioresistant MDA-MB-231-RR cells. Using transwell analysis, we further found that knockdown of MALAT1 or NEAT1 suppressed the cell migration or invasion of radioresistant MDA-MB-231-RR cells. Conclusion MALAT1 or NEAT1 involves in cell proliferation, self- renewal and cell invasion properties of radioresistant TNBC cells. We believe that the results will provide new insights in the biological role of NEAT1 in the maintenance and radioresistant behavior of TNBC CSCs and the use of NEAT1 as new predictor for future breast cancer radiotherapy. PO-303 Proteomic analysis for testis of mice exposed to carbon ion radiation H. Zhang 1 , H. Li 1 1 Institute of Modern Physics- Chinese Academy of Sciences, Department of Radiation Medicine, Lanzhou, China Purpose or Objective To investigates the mechanism of action of heavy ion radiation (HIR) on mouse testes. Material and Methods The testes of male mice subjected to whole body irradiation with carbon ion beam (0.5 and 4 Gy) were analyzed at 7 days after irradiation. A two-dimensional gel electrophoresis approach was employed to investigate the alteration of protein expression in the testes. Spot detection and matching were perfored using the PDQuest 8.0 software. A difference of more than threefold in protein quantity (normalized spot volume) is the standard for detecting differentially expressed protein spots. A total of 11 differentially expressed proteins were found. Protein identification was perfomred using matrix-assisted laser desorption/ionization tandem time-of-flight mass Radiobiology: Radiobiology of particles and heavy ions

spectrometry (MALDI-TOF-TOF). Nine specific proteins were identified by searching the protein sequence database of the National Center for Biotechnology Information. Results These proteins were found involved in molecular chaperones, metabolic enzymes, oxidative stress, sperm function, and spermatogenic cell proliferation. HIR decreased glutathione activity and increased malondialdehyde content in the testes. Given that Pin1 is related to the cell cycle and that proliferation is affected by spermatogenesis, we analyzed testicular histological changes and Pin1 protein expression through immunoblotting and immunofluorescence. Alterations of multiple pathways may be associated with HIR toxicity to the testes. Conclusion Our findings are essential for studies on the development, biology, and pathology of mouse testes after HIR in space or radiotherapy. PO-304 Multifunctional magnetic nanostructures (Gadolinium- Ironoxide) for potential cancer theranostics P.R. Rauta 1 , B. Vishwanathan 2 1 MD Anderson, Oncology Res, Houston, USA 2 Vydehi Institute of Medical Science and Research Center - Bangalore- IN, Dept. of Radiation Oncology, Bangalore, India Purpose or Objective In the nanoparticle research involving cancer therapy, there exists limitations in targeting cancer cells and uniform distribution within the tumor. In this proposal, we propose combined use of iron oxide (IO) nanoparticles and nonspecific extracellular lanthanides (gadolinium chelate (Gd)) in order to further improve the sensitivity and specificity of tumor imaging and hyperthermia application. Gadolinium in the nanostructure acts as a potential radio sensitizer. Material and Methods In the current project, magnetic nanostructures (MNS) were constructed by conjugating APTES-Gd 2 O 3 NPs with OA- Fe 3 O 4 NPs with the help of EDC/NHS catalysis and characterized. The final magnetic nanostructures; (APTES- Gd 2 O 3 NPs)-(OA- Fe 3 O 4 NPs) were evaluated for high-resolution magnetic resonance imaging (MRI) and radiation-hyperthermia applications in vitro as well as in vivo mice tumors. Results Successful synthesis of magnetic nanostructures (MNS) (45 ± 11 nm) was achieved through EDC/NHS catalysis. The synthesized NPs are hemocompatible and cytocompatible over a wide concentration range (up to1000 µg/mL), high relaxivity and have a high affinity towards cancer cells. Upon applying magnetic hyperthermia, the formulated nanostructure was able to kill the cancer cells in vitro effectively. In vitro magnetic hyperthermia study was proved by measuring the cell cytotoxicity as MTT assay showed that up to 48 hours incubation of cells after hyperthermia treatment (50 µg/ml solution of IO NPs, 10 kW/20 min), cell viability reduced to 42±3%. Moreover, owing to the T1 shortening ability of our synthesized nanostructures also show an excellent T1 MRI contrast performance. The hyperthermic radio sensitization effect of magnetic nanostructures [(APTES- Gd 2 O 3 NPs)-(OA- Fe 3 O 4 NPs)]was proved both in vitro (cell lines) and in vivo (mice) when compared with the control arm (without Gd 2 O 3 NPs and Fe 3 O 4 NPs) that receives only radiation, whereas the test arms (with Gd 2 O 3 NPs and Fe 3 O 4 NPs) received induction hyperthermia with ironoxide nanoparticles and radiation in one arm and induction hyperthermia with ironoxide-gadolinium nanostructure along with radiation in the other arm. In the 3 groups, the