ESTRO 38 Abstract book

S187 ESTRO 38

control, CAR, RT, RT+CAR. Effects on cell viability were measured using XTT assay. DNA-DSB was done by quantifying foci of positive γ-H2AX staining. Cell bioenergetics were measured using Cell mitostress test (Seahorse Bioscience), and ROS production detected with the probe CM-H 2 DCFDA. Results Clonogenic assay: CAR reduced the number of colonies in non-irradiated cells, and decreased SF of A549 cells at increasing RT doses, not observed in BMACs. At short term, CAR reduced proliferation of the three cell lines and affected their cell cycle, but it only increased the percentage of A549 in the G2/M radiosensitive phase. In A549 cells CAR reduced cell viability, increased frequency of DNA-DSB, and production of ROS. These effects were exacerbated in RT+CAR; opposite effects were observed in normal cells. In terms of A549 cells bioenergetics, CAR reduced their metabolic potential (ability to meet energy demands via respiration/glycolysis), CAR did not induce negative effects on normal cells metabolic potential.

tissue effects prior to clinical studies. We hypothesize that Notch inhibition has a protective effect in cells exposed to radiotherapy and may represents a potential target for intervention to modulate normal tissue toxicity. Material and Methods We established and characterized primary lung organoids and air liquid interface system (ALI), pseudo-stratified cultures derived from primary human bronchial epithelial cells (PBECs) from 6 different donors. In these cultures, basal cells proliferate and differentiate into ciliated and mucous/secretory cell types resembling the human bronchus. We irradiated lung epithelium with 2 and 4 Gy and early and late response to radiotherapy were evaluated. We investigated the consequences of blocking Notch signaling pathway using the pan-notch γ-secretase inhibitor DBZ (1uM) alone and when combined with irradiation (2, 4 Gy). Results Using immunofluorescence, western blot and q PCR we found that basal cells (p63 + , CK5 + ) cease proliferation (Ki67, EdU) at day 21 and mucous cell differentiation (Muc1/5ac + ) precedes ciliary differentiation (Ac-Tub + ) and both complete at day 28. Proliferation decreases overtime but inhibiting Notch in undifferentiated progenitors and in differentiated cells at day 21 increases p63 proliferation alone and even more in combination with radiotherapy. In all the 6 donors and in murine cultures Notch inhibition increases p63+basal progenitors and ciliated cells and decreases mucous cells alone and in combination with radiation. In irradiated cultures we observed increased pATM and pCHK2 12h and 24h post-irradiation when Notch signaling was inhibited. 53BP1 staining shows reduced DNA breaks 24h and 3 days post-irradiation when Notch was These data support the use of normal patient tissue for predictive toxicity, screening of combination treatments and disclose important novel interactions between Notch inhibition and radiotherapy. OC-0376 Radio-selective effects of natural occurring muscle-derived dipeptide in A549 and normal cell lines N. Ybarra 1 , J. Seuntjens 1 1 McGill University, Oncology Department, Montreal, Canada Purpose or Objective Radiotherapy (RT) causes morbidity and long-term side effects. A challenge in RT is to maximize cancer cell killing while minimizing damage to normal tissue. The ideal radio-protector selectively improves survival and limits damage to normal tissues while reducing survival or proliferation of cancer cells. Muscle-derived dipeptide, L- carnosine (CAR) has been described as a potent antioxidant, with radio-protective, but also anticancer properties, affecting the cell cycle of cancer cells. We aimed to test CAR effects in 3 cell types affected by RT: cancer cells, differentiated and undifferentiated normal cells. We hypothesized that 1) CAR antioxidant properties will confer protection to normal cells against RT while preventing cancer cell proliferation, and 2) CAR may act as a radiosensitizer of cancer cells due to its effect on their cell-cycle progression. Material and Methods The radio-selective effects of CAR were tested in cell lines: a) differentiated normal cells (human lung fibroblasts, HLF), b) normal undifferentiated cells (bone marrow adherent cells, BMAC), and c) lung cancer cell line (A549 cells). Treatment consisted of adding CAR to the media of growing cells. Cell cycle progression and short- term effects in proliferation were tested in control and CAR treated cells. Clonogenic assay, also performed in control and CAR-treated, was used to test CAR long-term effects in cells exposed to different radiation doses. In addition, the 3 cell lines were randomized in four groups: inhibited. Conclusion

Conclusion CAR increased radio-sensitivity of A549 cancer cells by selectively increasing ROS production and negatively affecting A549 cell bioenergetics, therefore reducing cells viability and DNA-DSB repair capacity. CAR had either no effect or reduced RT-induced damage in normal cells, depending on the cell type. CAR is a versatile naturally occurring compound, that could improve RT-induced cancer cell killing, while reducing the damage to normal differentiated and undifferentiated cells. OC-0377 Individual radiation toxicity prediction, how does mtDNA influence normal tissue response? M. Van Gisbergen 1 , S. Masroor 2 , E.E.J.M. Smeets 1 , M.J. Verhesen 1 , A.P.M. Stassen 3 , L. Dubois 1 , C. Oberije 2 , H.J.M. Smeets 3 , P. Lambin 1,2 1 GROW - School for Oncology and Developmental Biology- Maastricht Comprehensive Cancer Centre- Maastricht University Medical Centre, Department of Precision Medicine- The M-Lab, Maastricht, The Netherlands; 2 GROW - School for Oncology and Developmental Biology- Maastricht Comprehensive Cancer Centre- Maastricht University Medical Centre, Department of Precision Medicine- The D-Lab, Maastricht, The Netherlands ; 3 GROW - School for Oncology and Developmental Biology- Maastricht University Medical Centre, Department of Genetics and Cell Biology, Maastricht, The Netherlands