ESTRO 37 Abstract book

ESTRO 37

S593

effective than postoperative RT in inhibiting local tumor recurrence. It has been previously shown that fluids obtained postoperatively from breast cancer patients after breast-conserving surgery (BCS) can stimulate the invasiveness of tumor cells, but this effect is inhibited in IORT-treated patients. One hypothesis is that IORT alters the tumor microenvironment by modulating the wound healing response. The epithelial-mesenchymal transition (EMT) program plays a critical role in promoting metastasis in epithelium-derived carcinoma. Given this context, the aim of the present study was to evaluate the mechanisms that influence the decreased tumorigenic potential of post-operative WF in patients treated with BCS and IORT. We hypothesized that wound fluids obtained postoperatively from patients after IORT would present a bystander effect (RIBE) that induces a radiobiological response in unirradiated cells and modifies their phenotype. Material and Methods To confirm this hypothesis, cells collected from patients after BCS alone (i.e., without IORT) were incubated with WF together with a RIBE medium and the phenotype of these cells was compared to WF from patients who underwent BCS plus IORT. Firstly, changes in the CSC phenotype were analyzed by flow cytometry. Then the changes in EMT program were analyzed both at transcript and protein level. Lastly, a scratch assay was performed to determine the possible role of WF on the migration of breast cancer cells. Results Our findings show that wound fluids stimulate the CSC phenotype and EMT program in MCF7 and MDA-MB-468 breast cancer cell lines. This effect was partially abrogated when the cells were incubated in wound fluids collected from breast cancer patients after breast- conserving surgery followed by IORT treatment. Additionally, we confirmed the role of the radiation- induced bystander effect in altering the properties of the WF to induce the CSC phenotype and EMT program. Conclusion The results presented here may be relevant not only to improve our understanding of the biological processes underlying changes in the properties of WF after IORT treatment, but may also be relevant for identifying effective treatments for breast cancer. PO-1055 High intensity treadmill running reduces tumour hypoxia in mice. S. Lønbro 1 , T. Wittenborn 1 , P. Byrialsen Elming 1 , M. R. Horsman 1 1 Aarhus University Hospital, Dept. of Experimental Clinical Oncology, Århus C, Denmark Purpose or Objective Low blood perfusion and hypoxia are characteristic features of tumours and are factors of resistance to radiation and chemotherapy. A few rodent studies have shown that aerobic exercise, that has no severe side- effects, may improve perfusion and reduce hypoxia, however the optimal exercise intensity and timing of the effect on the tumour response during radiation and chemotherapy remain uninvestigated. The aim of our study was to investigate the acute effect of one exercise bout of either low, moderate, or high intensity aerobic exercise on tumour perfusion and hypoxia. Material and Methods Two weeks after injection of the C3H mammary carcinoma in the mammary fat pad, 24 female CDF1 mice were allocated to either a control group (no exercise) or

three groups performing low (6 m/min), moderate (12 m/min) or high intensity (18 m/min) treadmill running for 30 minutes (n=6 for each group). Just prior to running all mice were injected (i.p.) with Pimonidazole (60 mg/kg) and immediately after exercise they were injected (i.v.) with Hoechst 33342 (10 mg/kg). Exactly 1 minute later the mice were sacrificed, tumours excised, and histological sections prepared. Hypoxia could be determined from the degree of Pimonidazole binding, while analysis of the Hoechst 33342 staining enabled us to analyses perfused vessels in the tumour. The results were statistically compared to similar measurements in the control tumours using a Student’s T-test (p<0.05). Results Pimonidazole binding revealed a hypoxic fraction (HF) of 8.7±3.7% in tumours from control animals. This was not significantly changed by low intensity (HF = 8.5±3.2%) or moderate intensity (HF = 10.3±3.7%) running. However, for those mice exposed to the high intensity running schedule, the tumour hypoxic fraction was significantly reduced to 4.3±2.2% (p=0.03). The Hoechst 33342 analyses on tumour perfusion are currently pending. Conclusion Our data show that mice running at high intensity for 30 minutes elicit an acute reduction in the hypoxic fraction in the tumour when compared to sedentary mice or mice running at both moderate and low intensities. Our future studies will focus on how long the reduction in hypoxia is maintained after running stops and how the exercise regime can be used to improve tumor treatment- response, especially to radiation. The Danish Cancer Society and the A.P. Møller Foundation are acknowledged for funding the current studies. PO-1056 Decipering the mechanism of ADAM17- mediated radioresistance in NSCLC S. Bender 1 , P. Knobel 1 , A. Sharma 1 , A. Broggini-Tenzer 1 , M. Pruschy 1 1 University Hospital Zürich, Department of Radiation Oncology, Zurich, Switzerland Purpose or Objective The therapeutic response of ionizing radiation (IR) is imparted by genomic instability and DNA damage. However, IR also triggers intracellular signaling processes which lead to the secretion of various factors being involved in resistance mechanisms. Recently, we have shown that radiotherapy activates ADAM17 (A Disintegrin And Metalloprotease 17) in NSCLC, which mediates IR- induced treatment resistance. Our new data demonstrate a link between ADAM17, chromatin remodeling via the histone methyltransferase SUV39H1 and the DNA damage response. Material and Methods Clonogenic survival and xenograft tumor growth delay assays were performed in response to IR in inducible shRNA-targeted tumor cell lines and in combination with small molecular agents and a novel ADAM17-directed inhibitory antibody. Chromatin remodeling and DNA damage signaling were investigated by immunofluorescence staining and Western blotting. Results Radiotherapy activated ADAM17 in NSCLC, which resulted in shedding of multiple survival factors, growth factor Poster: Radiobiology track: Radiobiology of lung cancer