e21078 Background: The NovoTTF-100A is a device that emits an alternating electric field (TTField) that kills mitotic cells and has been FDA-approved for the treatment of recurrent glioblastoma. Exposure to the TTField resulted in impaired cytokinesis and asymmetric chromosome segregation. To further elucidate its mechanism of action, we performed experiments using synchronized tumor cells and TTField-treated xenografts. Methods: Biochemical analysis of cell cycle-specific proteins, timelapse movies, and immunoflourescence microsopy were used to examine the effects of TTField on synchronized tumor cells. Xenografts treated with TTField were analyzed for the presence of phospho-Histone H3 and cell cycle-specific epitopes. Results: Cells exposed to TTField as they transited through M-phase exhibited persistence of phospho-Histone H3 while Securin levels decreased, suggesting that these cells transit through metaphase to anaphase but were delayed in mitotic exit. Immunoflourescence of treated cells showed ev...