Abstract 2011: Tumor treating fields induce cellular and morphologic changes including disruption of intercellular communication networks in malignant pleural mesothelioma
Authors: Sarkari Akshat , Korenfeld Sophie , Ladner Katherine , Wong Phillip , Martinez Antonia , Dor-On Eyal , Giladi Moshe , Nain Amrinder , Lou Emil 
Published: July 2021

Tumor Treating Fields (TTFields) is a novel therapeutic strategy that uses alternating electric fields to disrupt mitosis in actively dividing cells through exertion of dielectrophoretic force and dipole alignment on microtubule subunits. However, the additional effects of TTFields on cellular morphology and communication remain unclear. Tunneling nanotubes (TNTs) are ultrafine F-actin-based protrusions that facilitate intercellular communication through cell-cell contact, including efficient transport of molecular cargo that accelerate invasive potential and chemoresistance. We hypothesized that by creating dielectrophoretic force on polar actin subunits, treatment with TTFields would lead to sustained disruption or prevention of formation of MPM TNTs.

TTFields (200 kHz) were applied at 0.5 or 1.0 V/cm to VAMT and MSTO MPM cell lines using the Inovitro system (Novocure). TNT index (average # of TNTs/cell) was determined at 0, 24, 48, and 72 hours of TTFields application. At the 72 hour period, TTFields were discontinued and assessment for recovery of TNT formation was performed after an additional 24 hours. Cell viability was determined by staining with NucGreen 488 dye. We also used time-lapse microscopy with concurrent application of TTFields and the chemotherapeutic agents cisplatin and pemetrexed to analyze effects on TNTs and functional cargo transfer.

Application of continuous TTFields at 1.0 V/cm, but not at 0.5 V/cm, suppressed TNT formation by 48.9% in MSTO (p=0.005). This suppression was achieved at the 48-hour time point and was independent of cell proliferation. No significant differences in TNT index were noted for VAMT. Cell viability was consistently above 95% at all time points for both cell lines at the stated frequency and intensities. Cargo transfer rates were lower in experimental groups treated with TTFields and either cisplatin, pemetrexed, or both.

Here, we show that treatment with TTFields suppresses formation of TNTs between MSTO cells, but not VAMT, suggesting additional factors that may determine susceptibility to TTFields treatment. Additionally, TTFields treatment of MSTO decreased the function of TNTs in these cells, as demonstrated by lower cargo transfer rates. In sum, these data identify effects of TTFields on TNTs as a novel mechanism for this therapeutic modality.

Citation Format: Akshat Sarkari, Sophie Korenfeld, Katherine Ladner, Phillip Wong, Antonia Martinez, Eyal Dor-On, Moshe Giladi, Amrinder Nain, Emil Lou. Tumor treating fields induce cellular and morphologic changes including disruption of intercellular communication networks in malignant pleural mesothelioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2011.