ESTRO 2022 - Abstract Book

S1620

Abstract book

ESTRO 2022

Clearance of senescent cells using senolytic drugs has been shown to represent a potential therapeutic alternative to ameliorate radiotherapy-induced xerostomia. Therefore, our aim is to develop an efficient method to screen for potent senolytic drugs in a 3D salivary gland organoid model Materials and Methods Since senescent cells possess anti-apoptotic properties, we selected several drugs targeting diverse apoptosis related pathways. (Sham-)irradiated salivary gland organoids were treated with different doses of candidate drugs to obtain optimal responses. As a measure of senolytic activity a Caspase-3/7 fluorogenic substrate was added together with the selected drugs to detect increases in caspase activity, resulting in bight fluorescent responses in apoptotic cells. Caspase-3/7 fluorescent activity following drug treatment was visualized in real-time using an IncuCyte S3. Using this methodology, drug concentrations that efficiently induced apoptosis in irradiated cells but were not/less toxic to unirradiated cells were used to verify the elimination of senescent cells and any corresponding changes in the organoid forming efficiency (OFE) of irradiated salivary gland cells. Results We selected optimal doses for 17-DMAG, ARV-825, Dasatinib + Quercetin, TH588 and Nutlin3a that induce apoptosis only in irradiated organoids. Of these, 17-DMAG and Nutlin3a treated organoids showed increased self-renewal capacity after irradiation, with Nutlin3a having a more favorable toxicity profile. Furthermore, treatment with Nutlin3a resulted in a reduction of senescent markers in irradiated organoids, and a transcriptional increase in p53 target genes. Conclusion We conclude the screening for drugs that show senolytic activity without hampering stem cell expansion (as measured by organoid forming efficiency) may be a promising methodology for the identification of compounds with potential applications in post-radiotherapy regenerative medicine. 1 Kyung Hee University Hospital at Gangdong, College of Medicine, Kyung Hee University, Department of Radiation Oncology, Seoul, Korea Republic of; 2 College of Medicine, Seoul National University, Cellular Degradation Biology Research Center and Department of Biomedical Sciences, Seoul , Korea Republic of; 3 AUTOTAC Inc, AUTOTAC Inc, Seoul , Korea Republic of; 4 College of Medicine, Konyang University, Department of Biochemistry, Daejeon, Korea Republic of; 5 Kyung Hee University Hospital at Gangdong, College of Medicine, Kyung Hee University, Department of Radiation Oncology, Seoul , Korea Republic of Purpose or Objective The neuropathological features of Alzheimer’s disease (AD) include the accumulation of amyloid- β (A β ) and hyperphosphorylated tau aggregates. Recently, low-dose ionizing radiation (LDIR) has emerged as a promising therapeutic approach for AD. This modality is currently being evaluated in clinical trials for patients with the neurologic disorder. To enhance the efficacy of LDIR, we employed the AUTOphagy-TArgeting Chimera (AUTOTAC) technology in combination with LDIR. Materials and Methods AUTOTAC utilizes bifunctional molecules composed of target-binding ligands (TBLs) linked to autophagy-targeting ligand (ATLs). The synergistic efficacy of AUTOTAC and LDIR was validated using 11-month-old 5X FAD mice that accumulate extracellular A β plaques in the brain. The mice received fractionated therapy at 300 cGy (60 cGy per fraction for five times, radiation therapy regimen given over three weeks) and injected with the AUTOTAC compound ACT-108 (10 mg per kilogram, three times per week) that was demonstrated to eradicate intracellular phospho-tau aggregates from murine brains. Results The combination treatment significantly improved the behavior as compared with the radiation alone treatment ( p *= 0.0223) or ACT-108 alone treatment ( p ***= 0.0009). In addition, the combination treatment group also improved the cognition ( p *=0.0458) as compared with the radiation alone treatment group ( p = 0.7178) or ACT-108 alone treatment group ( p = 0.7889). Conclusion These results provide a possibility that extracellular A β plaques may be degraded through the combinational treatment of AUTOTAC and LDIR. PO-1821 Synergistic efficacy by combination of AUTOTAC and low dose radiation in Alzheimer’s disease J.S. Kim 1 , S.H. Lee 2 , E. Ko 3 , S.H. Kim 3 , K.W. Sung 2 , C.H. Ji 2 , M. Moon 4 , Y.T. Kwon 2 , W.K. Chung 5

PO-1822 Ultra-high dose rate FLASH effect on head and neck cancer cells and normal salivary gland in mice

E. Kim 1 , K. Yang 1 , M. Kim 1 , W.I. Jang 1 , H. Kim 2 , M. Park 3 , J. Kim 3

1 Korea Institute of Radiological and Medical Sciences, Radiation Oncology, Seoul, Korea Republic of; 2 Korea Institute of Radiological & Medical Sciences, Clinical Translational Research Team, Seoul, Korea Republic of; 3 Korea Institute of Radiological and Medical Sciences, Radiation Therapeutics Development Team, Seoul, Korea Republic of

Purpose or Objective