Tumor Treating Fields (TTFields) Hinder Cancer Cell Motility through Regulation of Microtubule and Acting Dynamics

Our plain-English summary of Tumor Treating Fields (TTFields) Hinder Cancer Cell Motility through Regulation of Microtubule and Acting Dynamics, by T. Voloshin, R.S. Schneiderman, A. Volodin, et al (Cancers, 2020).

The study

• Authors: T. Voloshin, R.S. Schneiderman, A. Volodin, R.R. Shamir, N. Kaynan, E. Zeevi, L. Koren, A. Klein-Goldberg, R. Paz, M. Giladi, Z. Bomzon, U. Weinberg, Y. Palti
• Journal: Cancers
• Published: 2020;12(10)
• Cited by: 84 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Tumor Treating Fields (TTFields) are noninvasive, alternating electric fields within the intermediate frequency range (100-300 kHz) that are utilized as an antimitotic cancer treatment. TTFields are loco-regionally delivered to the tumor region through 2 pairs of transducer arrays placed on the skin. This novel treatment modality has been FDA-approved for use in patients with glioblastoma and malignant pleural mesothelioma based on clinical trial data demonstrating efficacy and safety; and is currently under investigation in other types of solid tumors. TTFields were shown to induce an anti-mitotic effect by exerting bi-directional forces on highly polar intracellular elements, such as tubulin and septin molecules, eliciting abnormal microtubule polymerization during spindle formation as well as aberrant cleavage furrow formation. Previous studies have demonstrated that TTFields inhibit metastatic properties in cancer cells. However, the consequences of TTFields application on cytoskeleton dynamics remain undetermined. In this study, methods utilized in combination to study the effects of TTFields on cancer cell motility through regulation of microtubule and actin dynamics included confocal microscopy, computational tools, and biochemical analyses. Mechanisms by which TTFields treatment disrupted cellular polarity were (1) interference with microtubule assembly and directionality; (2) altered regulation of Guanine nucleotide exchange factor-H1 (GEF-H1), Ras homolog family member A (RhoA), and Rho-associated coiled-coil kinase (ROCK) activity; and (3) induced formation of radial protrusions of peripheral actin filaments and focal adhesions. Overall, these data identified discrete effects of TTFields that disrupt processes crucial for cancer cell motility.

In plain English

This laboratory study of Tumor Treating Fields (TTFields), alternating electric fields used to treat cancer, was by authors employed by Novocure, the device maker. It did not study asbestos or mesothelioma cells; mesothelioma appears only because TTFields are FDA-approved for malignant pleural mesothelioma. TTFields were applied to human glioblastoma and lung adenocarcinoma cell lines in dishes, and to mouse immune cells. In glioblastoma cells, TTFields significantly reduced invasion in every line tested, reduced spreading of cell clusters, and slowed migration into a cell-free gap. Migration was slowest with the field perpendicular to movement. Treated cells showed less microtubule staining, attached more firmly, and had larger, more numerous focal adhesions. Phosphorylation of the signaling protein GEF-H1 increased, as did the activity of RhoA and ROCK. At 200 kHz for 3 hours, no differences were seen in migration of mouse T cells or dendritic cells, with or without the attractant CCL19. The authors concluded their study offers a possible mechanism linking TTFields' microtubule effects to reduced cancer cell motility. They had not tested TTFields' effect on the cytoskeleton of non-cancerous cells.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: laboratory (in vitro) experiments on cultured cancer cell lines, plus in vitro migration tests on immune cells isolated from mice
• Who was studied: Human glioblastoma cell lines (U-87 MG, A-172, LN-229, LN-18, and a line written as LN-299) and human lung adenocarcinoma cell lines (A549, H1299), obtained from the American Tissue Culture Collection. The study also used T cells and bone marrow derived dendritic cells from 5 to 7 week old C57BL/6 mice. Experiments were done at Novocure Ltd., Haifa, Israel.
• Exposure: TTFields (alternating electric fields), not asbestos. The methods give an intensity of 1.75 V/cm (RMS) at 150 kHz for the lung adenocarcinoma lines and 200 kHz for the glioblastoma lines. The fields were applied in one direction or in two alternating directions, for periods from minutes up to 24 or 48 hours.
• Main results:
  • TTFields significantly reduced invasion of glioblastoma cells through a Matrigel-coated filter, compared with untreated controls, in all four cell lines tested (U-87 MG, A-172, LN-229, LN-18).
  • In three-dimensional spheroids embedded in matrix, TTFields significantly decreased dispersal of U-87 MG and A-172 cells.
  • In wound healing assays with U-87 MG and A-172 cells, the cell-free gap was made with culture inserts. TTFields significantly reduced cell migration velocity compared with untreated controls.
  • In A-172 cells, migration velocity was significantly lower when one-direction TTFields were applied perpendicular to the direction of cell movement than when they were applied parallel to it.
  • In glioblastoma cells at the wound edge, microtubule fluorescence was significantly lower than in controls, whichever direction the TTFields were applied.
  • Fewer TTFields-treated cells than control cells had the microtubule-organizing center (MTOC) positioned between the nucleus and the leading edge.
  • After 24 hours of TTFields, cells detached less readily from the dish than untreated controls in all treated cancer cell lines (U-87 MG, A-172, LN-229, A549, H1299).
  • In A-172 and LN-229 cells, TTFields increased focal adhesion size and number and produced a dense meshwork of actin filaments around the cell periphery.
  • In A-172 and LN-229 cells, TTFields applied for 3 to 30 minutes produced a significant, short-lived increase in RhoA activity.
  • TTFields promoted phosphorylation of GEF-H1 in A-172 and LN-229 cells.
  • TTFields significantly increased ROCK activity in treated glioblastoma cells.
  • Migration of mouse dendritic cells and T cells toward CCL19 was tested during 3 hours of TTFields at 200 kHz.
  • At 200 kHz, no differences from controls were observed in the number of mouse T cells or dendritic cells that migrated, with or without the attractant CCL19.
• The authors' conclusion: The authors concluded that their study provides a possible unifying molecular mechanism. In their view, it links TTFields' disruption of microtubules to changes in actin organization and in the cell polarity needed for cancer cell motility.
• Limitations the authors state:
  • The authors had not tested the effect of TTFields on the cytoskeletal architecture of non-cancerous cells.
  • The authors stated that how cellular microtubules come to align with TTFields still needs further investigation.

Topics

Medical terms in this study, explained in our Lexicon: Tumor Treating Fields (TTFields), Pleural Mesothelioma, Clinical Trial.

Related studies

• Tumor Treating Fields (TTFields) downregulate the Fanconi Anemia-BRCA pathway and increase the efficacy of chemotherapy in malignant pleural mesothelioma preclinical models — H. Mumblat, A. Martinez-Conde, et al. (2021)
• Efficacy and immunogenic effects of Tumor Treating Fields (TTFields) in preclinical models of pancreatic ductal adenocarcinoma, with and without gemcitabine/nab-paclitaxel — T. Kan, T. Haj Khalil, et al. (2026)
• The transcriptomic fingerprint of cancer response to Tumor Treating Fields (TTFields) — K. Wainer-Katsir, A. Haber, et al. (2025)
• The schemes, mechanisms and molecular pathway changes of Tumor Treating Fields (TTFields) alone or in combination with radiotherapy and chemotherapy — G. Tanzhu, L. Chen, et al. (2022)
• A review of tumor treating fields (TTFields): advancements in clinical applications and mechanistic insights — X. Li, K. Liu, et al. (2023)
• Expert guidance on prophylaxis and treatment of dermatologic adverse events with Tumor Treating Fields (TTFields) therapy in the thoracic region — M.J. Anadkat, M. Lacouture, et al. (2022)

Browse more research in Cancers, or return to medical research.