Abstract 574: In vitro TTFields enhance the response to temozolomide or radiation in GBM cells from a newly diagnosed patient

Background: Tumor treating fields (TTFields) are FDA-approved for treatment of newly diagnosed and recurrent glioblastoma and are typically initiated after patients have undergone surgical resection, temozolomide, (TMZ) and radiotherapy. In this study, GBM cells generated from a tumor resected from a newly diagnosed glioblastoma patient were treated in vitro with TTFields ± TMZ or treated with in vitro TTFields followed by irradiation to determine if TTFields alter the response to the standard-of-care treatment modalities. Methods: Single-cell suspensions generated from tumor tissue obtained from a newly diagnosed patient were cultured in DMEM/F12 media with 10% fetal bovine serum and gentamicin. For the TMZ experiment, cells were plated on plastic coverslips (1 × 104cells/coverslip; n=4-6/group) and incubated overnight. TTFields (200 kHz; field intensity of ~1.6 V/cm). were applied with or without 50 µM TMZ for 5 days, followed by the XTT proliferation assay. For the radiation experiment, cells were plated on plastic coverslips (5 × 104cells/coverslip; n=3/group) and incubated overnight. TTFields (200 kHz; field intensity of ~1.6 V/cm). were applied for 3 days followed by irradiation with 0, 2, 4, or 6 Gy. Cells were harvested and plated to assess clonogenic potential. After 3 days, cells were stained with crystal violet and plates were scanned to determine cell counts. Data were analyzed by one-way ANOVA with Tukey's post-hoc test. Results: In the TTFields/TMZ experiment, control XTT values were 0.665 ± 0.052, TMZ only were 0.480±0.024, TTFields only were 0.550±0.080 and TTFields + TMZ were 0.164 ± 0.062 (mean ± SD; ANOVA p