ESTRO 36 Abstract Book

S543 ESTRO 36 _______________________________________________________________________________________________

PO-0983 Antrodia cinnamomea Regulates DNA Repair and Enhances Radiosensitivity of Esophageal Cancer Cells Y.M. Liu 1 , Y.J. Chen 2 , Y.K. Liu 3 , T.H. Tsai 4 1 Taipei Veteran General Hospital, Div. of Radiation Oncology- Dept. of Oncology, Taipei, Taiwan 2 MacKay Memorial Hospital, Department of Radiation Oncology, New Taipei City, Taiwan 3 Chang Gung University, Department of Chemical and Material Engineering, Taoyuan City, Taiwan 4 National Yang Ming University, Institute of Traditional Medicine, Taipei, Taiwan Purpose or Objective This study investigated the adjunctive effects of Antrodia cinnamomea mycelial fermentation broth ( AC -MFB), a Taiwanese medicinal fungus, in enhancing the radiosensitivity of esophageal cancer cells. in vitro and in vivo. Material and Methods Materials: Antrodia cinnamomea mycelial fermentation broth, Human CE81T/VGH squamous and BE3 adenocarcinoma esophageal cancer cells, BALB/c mice. Method: MTT assay, colony formation assay, DNA histogram study, γ-H2AX immunofluorescence assay, Western blotting assay, BALB/c mice animal model study. Results A colony formation assay showed that pretreatment with AC -MFB decreased the survival of irradiated esophageal cancer cells, with a maximum sensitizer enhancement ratio of 1.91 and 37% survival. A DNA histogram study showed that AC -MFB pretreatment enhanced cell cycle arrest at the G2/M phase, the most radiosensitive phase. An immunofluorescence assay and a Western blotting assay showed that AC -MFB delayed the abrogation of γ- H2AX, upregulated p21 expression, and attenuated the radiation-induced phosphorylation of ataxia telangiectasia-mutated kinase and checkpoint kinase 2. An in vivo validation study showed that AC -MFB treatment tended to have a synergistic effect with radiation on the tumor growth delay of CE81T/VGH cells in BALB/c mice. Conclusion These data suggest that this edible fungus product could enhance the effect of radiotherapy against esophageal cancer. PO-0984 Checkpoint HLA-G or its ligands ILT2/ILT4 changes radiosensitivity of renal carcinoma cell lines C. Hennequin 1 , M. Daouya 1 , D. Tronik-Le Roux 1 , J. LeMaoult 1 , N. Rouas-Freiss 1 , F. Desgrandchamps 1 , E. Carosella 1 1 Hôpital Saint-Louis, Research in Immuno-hematology, Paris, France Purpose or Objective HLA-G is an immune checkpoint physiologically implicated in maternal-foetal tolerance. It is also neoexpressed in many cancers and particularly in more than 50% of renal cancers. Stereotactic radiotherapy efficiency is at least in part mediated by the immune system, and could be modulated by the presence of immune checkpoints; for example the use of antibodies directed against PD1/PDL1 increased radiotherapy efficiency. We investigated the impact of expression of HLA-G or its ligands (ILT2/ILT4) on radiotherapy efficiency at the cellular level on renal carcinoma cell lines (RCCL). Material and Methods The effect of ionizing radiations (IR: 8 Gy) on the expression of HLA-G, ILT2 and ILT4 was evaluated on RCCL expressing or not HLA-G, ILT2 or ILT4. The impact of HLA- G, ILT or ILT4 expression on radiosensitivity was evaluated by clonogenic assays on transduced RCCL or controls. In order to explain the results obtained, the following mechanisms were investigated by cytofluorimetry: 1/ quantification of double-strand breaks (H2AX) 2/

effectively induced ubiquitination and degradation of Nrf2, and inhibited translocation of Nrf2 to the nucleus. Consequently, expression of Nrf2 downstream genes was reduced, and the Nrf2-dependent antioxidant system was suppressed. Endogenous ROS was higher than before ISL treatment, causing redox imbalance and oxidative stress in HepG2 cells. Moreover, pretreatment with ISL for 6 h followed by X-ray irradiation significantly increased γ- H2AX foci and cell apoptosis, and reduced clonogenic potential compared with cells irradiated with X-rays alone. In addition, HepG2 xenografts, ISL, and X-ray cotreatments induced greater apoptosis and tumor growth inhibition, when compared with X-ray treatments alone. Additionally, HepG2 xenografts, in which Nrf2 was expressed at very low levels due to ectopic expression of Keap1, showed that ISL-mediated radiosensitization was Keap1 dependent. Conclusion ISL inhibited the Nrf2-antioxidant pathway by increasing the levels of Keap1 and ultimately inducing oxidative stress via disturbance of the redox status. The antioxidant ISL possessed pro-oxidative properties, and enhanced the radiosensitivity of liver cancer cells, both in vivo and in vitro . Taken together, these results demonstrated the effectiveness of using ISL to decrease radioresistance, suggesting that ISL could be developed as an adjuvant radiosensitization drug. Disturbance of redox status could be a potential target for radiosensitization. PO-0982 Fused Toes Homolog (FTS) is a potential target for Notch-mediated radioresistance in cervical cancer W.Y. Park 1 , P.D. Subramania 1 , J.R. Yu 2 1 Chungbuk National University Hospital, Dept of Radiation Oncology, Cheongju, Korea Republic of 2 Konkuk University, Department of Environmental and Tropical Medicine, Chungju, Korea Republic of Purpose or Objective Radiation therapy is one of the major treatment modalities for cervical cancer. Increasing evidences suggest that cancer stem cells (CSC) in tumours contribute to radioresistance and recurrence. Notch pathway plays a vital role in maintenance of cancer stemness and its activation leads to disease progression and metastasis. FTS gene was initially identified as one of six genes deleted in a mouse mutant called Fused Toes, due to defects in limb development, and referred as FT1/FTS. However, the function of FTS has not been elucidated well in human. We previously reported that FTS plays an essential role in nuclear phosphorylation of EGFR and repair of DNA damage, and epithelial-mesenchymal transition. In this study, we evaluated the role of FTS in Notch signaling and CSCs. Material and Methods A human cervical cancer cell line (ME180) was used. Silencing of FTS was obtained using siRNA. Western blot and immunofluorescence was done to analyze the expression and localization of the proteins. Results Protein expression of Notch 1, cleaved Notch1, Notch 3, γ-secretase complex and its downstream Hes-1was increased by ionizing radiation and it was reduced by FTS- silencing. Spheroid formation ability and cancer stem cell markers Nanog, Oct-4A, Sox2 were reduced by FTS- silencing. Cell survival was decreased by FTS-silencing. Conclusion FTS is involved in the regulation of Notch signaling and CSC maintenance. FTS can be a target to overcome Notch– mediated radioresistance in cervical cancer.