P10.01.A A PATIENT-DERIVEDEX VIVO ORGANOID MODEL ALLOWS EVALUATION OF TUMOR TREATING FIELDS (TTFIELDS) EFFECTS ON GLIOBLASTOMA, ANAPLASTIC EPENDYMOMA AND OLIGODENDROGLIOMA SAMPLES

Abstract BACKGROUND The use of TTFields, which are alternating electric fields of low intensity (1-3 V/cm) and intermediate frequency (100-500 kHz), has shown its clinical efficacy in the treatment of newly diagnosed glioblastoma (GBM) patients at 200 kHz. Nevertheless, more knowledge is required for the prediction of individual tumors’ responsiveness to treatment. Recently, we developed patient-derived three-dimensional GBM tissue culture models to screen patient tumors for TTFields treatment susceptibility. Here, we extended these models to brain tumors beyond GBM, namely anaplastic ependymoma (AE) and oligodendroglioma. We cultured tumor-organoids as microtumors on murine organotypic hippocampal slice cultures (OHSCs) and subjected them to TTFields at 200 kHz. MATERIAL AND METHODS We prepared OHSCs by slicing the brains of mice 5-8 days postpartum to a thickness of 350 µm using a vibratome and culturing them for 14 days. We obtained organoids from freshly resected tumor tissue from three GBM, one AE, and one oligodendroglioma patient, each. The organoids were cultured for 14 days as well and then stained with carboxyfluorescein succinimidyl ester. Next, we placed the organoids onto the OHSCs and administered TTFields at 200 kHz and 1.5 V/cm for 72 h using the inovitro™ laboratory research system. We quantified microtumor growth by fluorescence imaging. RESULTS The three tumor entities, in particular organoids from GBM, AE and oligodendroglioma, grew as microtumors after being placed onto OHSCs. TTFields treatment at 200 kHz led to significantly decreased microtumor size of the three analysed GBM samples as well as the AE sample. However, the oligodendroglioma microtumor size was not significantly reduced. CONCLUSION Based on clinical experience, we expected that TTFields lead to a reduction in microtumor size. However, to our knowledge, we were the first to apply TTFields to patient-derived AE and oligodendroglioma samples. The lack of TTFields-effects on the latter might be due to different inter-patient sensitivity or suboptimal TTFields frequency. Nevertheless, our work is proof of principle that an organoid-based patient-derived 3D tissue culture model could be used to evaluate effects of TTFields on different brain tumor entities.