P11.20 Assessing TTFields-response and associated gene expression in various human cancer cell lines

BACKGROUND Various cancer cell lines were reported to be affected in an inhibitory manner of varying magnitude by tumor treating fields (TTFields). Here, we aimed to detect response markers for TTFields treatment by analyzing specific properties of cell lines according to their response pattern to these alternating electric fields of intermediate frequency and low intensity. MATERIAL AND METHODS We treated 45 cell lines of diverse types of human cancer with TTFields at their specific optimal frequency and equal nominal intensity of 1.7 V/cm for 72 h. In addition to investigating cytotoxicity and clonogenic potential, we used the Cancer Cell Line Encyclopedia (CCLE) database for further analysis: First, to functionally examine patterns of differentially expressed genes or mutations associated with response to TTFields; and second, to compare sensitivity to TTFields using pharmacological profiling (CCLE). RESULTS TTFields had a cytotoxic effect on tested cell lines of 50 % on average (range: 14–86% reduced cell counts), whereas the clonogenic effect varied between no effect and 88 % reduction in the number of colonies. With regard to differential gene expression and mutation analysis, our analysis detected upregulated pathways associated with migration, DNA damage repair response, oxidative stress, and hypoxia. Further, cells identified as having a better response to TTFields were also more sensitive to lapatinib, PHA-665752 and PLX-4720. CONCLUSION In this study, we determined the optimal frequency for maximum response to TTFields in numerous human cancer cell lines. Our results argue strongly for a vast effectiveness of TTFields treatment in cancer cells, and synergistic effects in combination with other therapeutic agents might be revealed in future studies using pharmacological profiling. Beyond that, further research is needed on the role of identified response-associated mutations.