Abstract 2652: Adjuvant therapeutic potential of hypothermia in the treatment of glioblastoma: An in vitro study
Authors: Fulbert Clémentine , Gaude Christophe , Chabardès Stéphan , Ratel David 
Published: September 2020

Abstract
Glioblastoma is a particularly aggressive and infiltrative brain tumor with an annual incidence of three per 100,000 adults worldwide. Despite multimodal treatments, associating surgical resection with combined radiotherapy and temozolomide-based chemotherapy [1], prognosis remains poor. Median survival is only 14 to 16 months because of tumor recurring in the resection margins in over 90% of patients, due to the activation of residual glioblastoma cells. Hence, there is a need for developing novel therapies that improve survival outcome. To handle this issue, we propose therapeutic hypothermia as an adjuvant treatment, to place tumor cells at the resection margin in a dormant state. The aim of our study is to evaluate the adjuvant therapeutic potential of moderate hypothermia by investigating in vitro its ability to prevent cancer cell growth. We previously published results demonstrating that continuous moderate hypothermia at 28 °C is able to significantly inhibit both cell proliferation and migration [2].
We performed in vitro experiments on four glioblastoma cell lines with different p53 status and various growth rates: A-172, U-251 MG, U-87 MG, and T98G. To study the adjuvant potential of moderate hypothermia, we investigated its inhibitory effects on the proliferation of glioblastoma cells exposed to different conditions. First, we studied the impact of different sequences in which cells were successively placed in hypothermic conditions then rewarmed to 37 °C. On the other hand, we compared the inhibitory effects of moderate hypothermia with current chemotherapy protocols. Finally, we investigated the therapeutic potential of combining chemotherapy with hypothermia.
Here, we showed that moderate hypothermia significantly inhibited glioblastoma cell proliferation even after rewarming to 37 °C, with a significant influence of hypothermic preconditioning duration. In addition, moderate hypothermia reduced cell proliferation far more than chemotherapy alone, with inhibitory effects up to eight times higher for chemoresistant cell lines. Finally, combining hypothermia with chemotherapy further reduced proliferation, with more than 95% inhibition even after returning glioblastoma cells to 37 °C.
Our results showed that glioblastoma cell proliferation was not fully restored upon returning to 37 °C, suggesting that the effects of moderate hypothermia on cell growth are not limited to direct conditioning, which is important for clinical applications. We also demonstrated that responses to moderate hypothermia were similar for all four glioblastoma cell lines whereas they presented different levels of sensitivity to chemotherapy, depending on their p53 status. Moreover, combining both therapeutic approaches significantly improved glioblastoma cell sensitivity to treatment for all cell lines, regardless of their p53 status. Finally, these results showed that moderate hypothermia has the potential to reduce inter-patient variability of treatment efficiency, and thus appears to be a relevant adjuvant therapy for use when treating glioblastoma patients.
[1] R. Stupp et al., "Effects of radiotherapy with concomitant and adjuvant temozolomide versus radiotherapy alone on survival⋯", Lancet Oncol., 2009.
[2] C. Fulbert et al., "Moderate hypothermia inhibits both proliferation and migration of human glioblastoma cells", J. Neurooncol., 2019.
Citation Format: Clémentine Fulbert, Christophe Gaude, Stéphan Chabardès, David Ratel. Adjuvant therapeutic potential of hypothermia in the treatment of glioblastoma: An in vitro study [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2652.