ESTRO 2023 - Abstract Book

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ESTRO 2023

The data shows that hypoxic cores could be detected 24h after spheroid formation. Inhibiting OXPHOS with 1 µ M IACS- 010759 alleviates hypoxia in spheroids, compared to the control spheroids (0 µ M IACS-010759), shown by a reduction in the green signal within 30 min after start of treatment, which persisted for several hours (Fig. 1A). Furthermore, the fraction hypoxia revealed that 1 µ M IACS-010759, as well as 0.33 µ M IACS-010759 were able to alleviate hypoxia, while 0.11 or 0.037 µ M IACS-010759 were unable to alleviate hypoxia in the center of the tumor spheroids. Spheroids treated with atovaquone (30 µ M) and metformin (3 mM or 9 mM) showed similar results. In addition, a dose-dependent response was observed after treatment with IACS-010759, atovaquone and metformin (Fig. 1B).

Conclusion We developed an in vitro model in which chronic hypoxia can be quantified over time using a Live Cell Imaging system. Using this system, we can determine the effect of several OXPHOS inhibitors on hypoxia alleviation. We showed that the OXPHOS inhibitors IACS-010759, atovaquone and metformin could alleviate hypoxia within 30 minutes after start of treatment and this sustained for several days in a dose-dependent manner. The observed reduction in hypoxia might sensitize hypoxic tumor cells for radiotherapy, immune checkpoint blockade and their combination.

PO-2213 The impact of the tumour microenvironment on head and neck SCC cell viability and radiosensitivity.

A. Chander 1,2 , A. Pellon Rodriguez 3 , V. Butterworth 4 , T. Guerrero Urbano 5 , A. Kong 6,5 , M. Lei 2 , I. Petkar 5 , T. Ng 6 , D. Moyes 7 , M. Reis Ferreira 1,2 1 King's College London , Centre for Host-Microbiome Interactions , London, United Kingdom; 2 Guy's and St Thomas' NHS Foundation Trust , Oncology , London, United Kingdom; 3 King's College London , Centre for Host-Microbiome Interactions , London , United Kingdom; 4 Guy's and St Thomas' NHS Foundation Trust, Radiotherapy Physics , London , United Kingdom; 5 Guy's and St Thomas' NHS Foundation Trust , Oncology , London , United Kingdom; 6 King's College London , School of Cancer and Pharmaceutical Sciences , London, United Kingdom; 7 King's College London, Centre for Host-Microbiome Interactions , London, United Kingdom Purpose or Objective Head and neck squamous cell carcinoma (HN-SCC) is an immunosuppressive disease with functional impairment of tumour- infiltrating lymphocytes including natural killer (NK) cells, which are critical in cancer immune surveillance. 2D co-culture models can be utilised to examine inter-relationships between different groups of cells in the tumour and normal tissue microenvironment, such as between cancer and immune cells. These cell culture models are also often used to study the effects of radiation in cancers and normal tissues. However, in these settings, radiation is commonly delivered using orthovoltage irradiators in single dose fractionation schedules, which is not reflective of clinical radiotherapy applications. We have developed a 2D co-culture model of HN-SCC and NK cells using a clinically operational linear accelerator and evaluated the impact of NK cells on radiation-mediated cancer cell death. Materials and Methods The 2D co-culture model consists of human buccal SCC cells (TR146 cell line) and human leukaemic NK cells (KHYG-1 cell line) added either before or after irradiation at 5:1 to 10:1 NK:HN-SCC ratios. Tumour cell death was assessed using an ATP-based cell viability assay at D4-6 post-irradiation. Irradiation was carried out using a clinically-operational linear accelerator at a range of doses including 2Gy, 5Gy and 10Gy in a single fraction. Fractionated radiation regimens were also carried out including 6Gy over 3 fractions (2Gy per fraction) and 15Gy over 3 fractions (5Gy per fraction). Significance was assessed with the ANOVA statistical test. Results The addition of NK cells prior to irradiation contributed more significantly to radiation-mediated HN-SCC killing, at effector to target ratios of 5:1 (p<0.0001). SCC viability was significantly reduced in 5:1 and 10:1 groups compared with the TR146 alone group irrespective of single fraction radiation dose (p<0.0001). There was no significant difference in SCC viability between the 5:1 and 10:1 groups. Additionally, there was no significant difference in SCC viability with the different single fraction radiation doses within 5:1 group and the 10:1 group.