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Cited by 217Microtubule and mitosis dynamicsElectromagnetic Fields and Biological EffectsMicrobial Inactivation Methods

Tumor Treating Fields Perturb the Localization of Septins and Cause Aberrant Mitotic Exit

Open access
Gera, Nidhi, Yang, Aaron, Holtzman, Talia S., Lee, Sze Xian, Wong, Eric T., Swanson, Kenneth D.·2015·PLOS ONE
DOI 10.1371/journal.pone.0125269PMC PMC4444126
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Abstract

The anti-tumor effects of chemotherapy and radiation are thought to be mediated by triggering G1/S or G2/M cell cycle checkpoints, while spindle poisons, such as paclitaxel, block metaphase exit by initiating the spindle assembly checkpoint. In contrast, we have found that 150 kilohertz (kHz) alternating electric fields, also known as Tumor Treating Fields (TTFields), perturbed cells at the transition from metaphase to anaphase. Cells exposed to the TTFields during mitosis showed normal progression to this point, but exhibited uncontrolled membrane blebbing that coincided with metaphase exit. The ability of such alternating electric fields to affect cellular physiology is likely to be dependent on their interactions with proteins possessing high dipole moments. The mitotic Septin complex consisting of Septin 2, 6 and 7, possesses a high calculated dipole moment of 2711 Debyes (D) and plays a central role in positioning the cytokinetic cleavage furrow, and governing its contraction during ingression. We showed that during anaphase, TTFields inhibited Septin localization to the anaphase spindle midline and cytokinetic furrow, as well as its association with microtubules during cell attachment and spreading on fibronectin. After aberrant metaphase exit as a consequence of TTFields exposure, cells exhibited aberrant nuclear architecture and signs of cellular stress including an overall decrease in cellular proliferation, followed by apoptosis that was strongly influenced by the p53 mutational status. Thus, TTFields are able to diminish cell proliferation by specifically perturbing key proteins involved in cell division, leading to mitotic catastrophe and subsequent cell death.

AI snapshot

Written from the paper’s full text.

TL;DR

Tumor Treating Fields (TTFields) at 150 kHz perturb the metaphase-to-anaphase transition, disrupting Septin localization and causing aberrant mitotic exit. Surviving cells show reduced proliferation and increased apoptosis in a manner influenced by p53 status.

Key findings

  • TTFields-treated cells progressed through metaphase but exhibited membrane blebbing coincident with metaphase exit; mitotic plate formation and metaphase exit timing were similar to controls (49.39 ± 1.988 min vs. 43.26 ± 2.088 min for plate formation; 47.04 ± 1.196 min vs. 44.36 ± 2.037 min for metaphase exit in Sham vs. TTFields, respectively), but outcomes differed markedly (Sham n = 130 vs. TTFields n = 85).
  • The Septin 2/6/7 heterotrimer had a calculated dipole moment of 2711 Debyes (D), about five standard deviations above the median 542.66 D from 14,960 protein structures; TTFields at 150 kHz significantly reduced Septin 7 localization to the anaphase spindle midline and cytokinetic furrow, with 500 kHz showing an intermediate effect (midline/total intensity ratios: Sham n = 10, 150 kHz n = 9, 500 kHz n = 8).
  • F-actin accumulation at the midline was significantly decreased in 150 kHz TTFields-treated cells (n = 16 sham, n = 17 TTFields), and Septin 7 re-localization to microtubules during spreading on fibronectin was reduced at 150 kHz (n = 152) versus Sham (n = 70), with 500 kHz intermediate (n = 104).
  • TTFields exposure during M phase, but not G1, significantly decreased subsequent cellular accumulation; p53+/+ HCT116 cells showed a significant decrease in BrdU incorporation and higher Annexin V positivity than p53-/- cells, with apoptosis peaking around 36 hours after treatment.

Methods

  • Cell lines: HeLa, MDA-MB-231, HCT116 p53+/+ and p53-/-, and MCF-7; cells were synchronized by double aphidicolin block or RO3306 CDK1 inhibitor and exposed to TTFields at 1 V/cm², 150 kHz or 500 kHz, 150 mA using Inovitro TTFields generators.
  • Analyses included FACS for Cyclin B, phospho-histone H3, DNA content, and BrdU incorporation; immunofluorescence and confocal microscopy for α-tubulin, Septin 7, PLK1, F-actin, and Myosin-IIA-GFP; live-cell time-lapse imaging with DRAQ5; gridded cell counts; and Annexin V staining for apoptosis.
  • Septin localization was quantified by midline-to-whole-cell intensity ratios or subjective microtubule association scores (1–3) by two independent blinded scorers.

Limitations

  • The paper states that no complete crystal structures exist for PLK1, ECT2, Anillin, or the centralspindlin heterotetramer, so dipole calculations focused on Septin; it also states that it could not detect p53 induction in TTFields-treated cultures, leaving the nature of p53 dependency unclear.
  • The paper notes that other mitotic proteins, such as the α/β-tubulin dimer with a dipole moment of 1660 D, may also be affected, and that TTFields could act upstream of Septin recruitment rather than directly on Septins.
  • Evident from the text: the work is in cultured cell lines and does not establish direct physical binding of TTFields to Septins or in vivo/clinical causality; mechanism is inferred from localization, timing, and frequency-dependent effects.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1371/journal.pone.0125269

Cites

Statistics

Nothing to recompute.

Claims the paper makes

0 of 37 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    The mitotic Septin complex consisting of Septin 2, 6 and 7 has a calculated dipole moment of 2711 Debyes (D).

    “The mitotic Septin complex consisting of Septin 2, 6 and 7, possesses a high calculated dipole moment of 2711 Debyes (D)”
    • Also stated in: § Cells treated with TTFields exhibit differences in mitotic progression · plain
      “we found that this protein complex possessed a high dipole moment of 2711 Debyes (D) with a directional vector that is orthogonal to the longitudinal axis of the complex”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [49] CE Felder, 2007, A server and database for dipole moments of proteins, Nucleic acids research source

      Not checked in the free run.

    • cites [50] M Sirajuddin, 2007, Structural insight into filament formation by mammalian septins, Nature source

      Not checked in the free run.

  • Findingown data

    After aberrant metaphase exit as a consequence of TTFields exposure, cells exhibit signs of cellular stress including an overall decrease in cellular proliferation.

    “cells exhibited aberrant nuclear architecture and signs of cellular stress including an overall decrease in cellular proliferation”
    Quote in the paperSubstantial claim
  • Findingcitation

    The Septin complex dipole moment is approximately five standard deviations higher than the median value of 542.66 D derived from 14,960 protein structures.

    “Significantly, this dipole moment is approximately five standard deviations higher than the median value of 542.66 D derived from the analysis of 14,960 protein structures [49].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [49] CE Felder, 2007, A server and database for dipole moments of proteins, Nucleic acids research source

      Not checked in the free run.

  • Findingown data

    After aberrant metaphase exit as a consequence of TTFields exposure, cells undergo apoptosis that is strongly influenced by p53 mutational status.

    “followed by apoptosis that was strongly influenced by the p53 mutational status”
    • Also stated in: § Introduction · plain
      “cells affected by TTFields exposure during mitosis subsequently exhibited p53-dependent decrease in proliferation and an increase in apoptosis”
    Quote in the paperSubstantial claim
  • Findingown data

    TTFields inhibit Septin association with microtubules during cell attachment and spreading on fibronectin.

    “as well as its association with microtubules during cell attachment and spreading on fibronectin”
    • Also stated in: § Cells treated with TTFields exhibit differences in mitotic progression · plain
      “cells that were exposed to TTFields at 150 kHz (n = 152) exhibited significantly less Septin 7 localization to microtubules”
    Quote in the paperSubstantial claim
  • May combine two claims. 36
  • Classified as probably not a substantial claim. 13
  • The quote only partly states this claim. 1

  • May combine two claims.

    Findingreasoning

    Cells affected by TTFields exhibit different fates, including death in anaphase or aberrant exit from mitosis similar to mitotic slippage.

    “As in the case with spindle poisons, which trigger the SAC, cells affected by TTFields exhibit different fates including death in anaphase or aberrant exit from mitosis similar to mitotic slippage.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Cells exposed to TTFields during mitosis show normal progression to metaphase but exhibit uncontrolled membrane blebbing that coincides with metaphase exit.

    “Cells exposed to the TTFields during mitosis showed normal progression to this point, but exhibited uncontrolled membrane blebbing that coincided with metaphase exit.”
    • Also stated in: § Cells treated with TTFields exhibit differences in mitotic progression · plain
      “TTFields-treated cells exhibited membrane disruption and blebbing at times following mitotic plate formation that corresponded closely to the time of metaphase exit in control cultures”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    TTFields-treated cells largely transit through mitosis at rates similar to control cells, whereas paclitaxel-treated cells exhibit a significant early and persistent accumulation of double positive cells.

    “TTFields-treated cells largely transited through mitosis at rates similar to control cells whereas paclitaxel-treated cells exhibited a significant early and persistent accumulation of double positive cells (Fig 1A).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The time intervals from chromatid condensation to metaphase plate formation and from metaphase plate to anaphase or TTFields-induced membrane contractions are similar between Sham-treated and TTFields-treated cultures.

    “Measurement of the time intervals between chromatid condensation and formation of the metaphase plate (C) and from the formation of the metaphase plate to either evidence of anaphase or TTFields-induced membrane contractions (D) were similar, 49.39 ± 1.988 min vs. 43.26 ± 2.088 min for plate formation and 47.04 ± 1.196 min vs. 44.36 ± 2.037 min for metaphase exit in Sham-treated vs TTFields-treat”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation

    TTFields-treated cultures show a small increase in mitotic cells at later time points relative to control cultures, demonstrating an increase in time in mitosis.

    “Similar to other studies [38], we noted a small increase in mitotic cells at later time points in the TTFields-treated cultures relative to control cultures demonstrating an increase in time in mitosis.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [38] ED Kirson, 2004, Disruption of cancer cell replication by alternating electric fields, Cancer research source

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    Cells exposed to TTFields persist longer in mitosis and possess a higher DNA content for a longer period relative to non-TTFields-treated control cells.

    “Cells exposed to TTFields persisted longer in mitosis and possessed a higher DNA content for a longer period relative to non-TTFields-treated control cells (Fig 1B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Cells undergoing mitosis within TTFields are able to form anaphase spindle midline structures even though Septins fail to localize to them, as shown by similar PLK1 levels.

    “However, since we detected similar levels of PLK1 within the anaphase spindles of TTFields-treated cells, this demonstrated cells undergoing mitosis within TTFields were able to form anaphase spindle midline structures even though Septins failed to localize to them (Fig 3D).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Mitotic spindles and metaphase plates form normally in TTFields-treated cells.

    “Mitotic spindles and metaphase plates formed normally in TTFields treated cells (F)”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Annexin V binding in p53+/+ HCT116 cells increased at 18 hours and peaked around 36 hours after the end of TTFields exposure.

    “We found that Annexin V binding increased at 18 hours and peaked around 36 hours (Fig 4E).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    While chromosomal migration to the mitotic plate appeared normal, the onset of membrane blebbing corresponded to the expected time of metaphase exit.

    “We found that while chromosomal migration to the mitotic plate appeared normal, the onset of the membrane blebbing corresponded to the expected time of metaphase exit.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In TTFields-treated cells, Septin localization to the anaphase spindle midline was markedly diminished and its microtubules were also disordered.

    “in TTFields treated cells we observe that Septin localization to the anaphase spindle midline was markedly diminished and its microtubules were also disordered.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    The Septin 2, 6 and 7 functional heterotrimer possesses an unusually large dipole moment of 2711D, which is more than five standard deviations (417.88 D) higher than the average value of 542.66 D derived from the analysis of 14,609 available protein crystal structures.

    “using the available crystal structures for the Septin 2, 6 and 7 functional heterotrimer we found that it possessed an unusually large dipole moment of 2711D, which is more than five standard deviations (417.88 D) higher than the average value of 542.66 D derived from the analysis of 14,609 available protein crystal structures [43].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [43] ED Kirson, 2007, Alternating electric fields arrest cell proliferation in animal tumor models and human brain tumors, Proceedings of the National Academy of Sciences of the United States of America source

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    A p53-dependent G0/1 block was observed after cells were exposed to TTFields with apoptosis occurring more than 24 hours after the affected mitosis with levels being greater in p53+/+ cells than in the knockouts.

    “A p53-dependent G0/1 block was observed after cells were exposed to TTFields with apoptosis occurring more than 24 hours after the affected mitosis with levels being greater in p53+/+ cells that in the knockouts.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Cells exposed to TTFields subsequently exhibit decreased proliferation with a failure to enter S phase and increased levels of apoptosis beginning more than 24 hours after TTFields exposure.

    “Indeed, consistent with this, we have found that cells exposed to TTFields subsequently exhibit decreased proliferation with a failure to enter S phase and increased levels of apoptosis beginning more than 24 hours after TTFields exposure.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Under cell culture conditions, TTFields forces affect cells during division, inducing violent plasma membrane contractions during mitosis and cell death.

    “Specifically, under cell culture conditions, these forces affected cells during division in a way that resulted in the induction of violent plasma membrane contractions during mitosis and cell death [38, 43].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [38] ED Kirson, 2004, Disruption of cancer cell replication by alternating electric fields, Cancer research source

      Not checked in the free run.

    • cites [43] ED Kirson, 2007, Alternating electric fields arrest cell proliferation in animal tumor models and human brain tumors, Proceedings of the National Academy of Sciences of the United States of America source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Alternating electric fields (TTFields) disrupt cells during mitosis within a narrow range of frequencies with peak activity between 100 and 200 kHz, while fields at 500 kHz or above have little measurable effect on cell biology.

    “It has recently been demonstrated that alternating electric fields referred to here as Tumor Treating Fields (TTFields), are able to disrupt cells during mitosis within a narrow range of frequencies with peak activity between 100 and 200 kHz; such fields have little measureable effect on cell biology at frequencies of 500 kHz or above, [38].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [38] ED Kirson, 2004, Disruption of cancer cell replication by alternating electric fields, Cancer research source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    TTFields diminish cell proliferation by specifically perturbing key proteins involved in cell division, leading to mitotic catastrophe and subsequent cell death.

    “Thus, TTFields are able to diminish cell proliferation by specifically perturbing key proteins involved in cell division, leading to mitotic catastrophe and subsequent cell death.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    TTFields perturb mitosis by interfering with normal Septin localization and function, leading to CCF dysfunction and aberrant mitotic exit.

    “we propose a mechanism of action where TTFields perturb mitosis by interfering with normal Septin localization and function leading to CFF dysfunction and aberrant mitotic exit.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    TTFields result in cellular derangement leading to decreased proliferation or death.

    “result in cellular derangement leading to decreased proliferation or death”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    TTFields interfere with the proper formation and/or regulation of the CCF.

    “These timing of these observations strongly suggested that TTFields interfered with the proper formation and/or regulation of the CCF.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The total dipole of the Septin hexamer is likely roughly the sum of the heterotrimers, thereby increasing the ability of TTFields to act on it.

    “Therefore, it is likely that the total dipole of this hexamer is roughly the sum of the heterotrimers thereby increasing the ability of TTFields to act on it.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The septin complex forms filaments associated with the microtubule cytoskeleton during interphase and diffuses within the cytoplasm upon cell rounding and microtubule de-polymerization.

    “The septin complex forms filaments associated with the microtubule cytoskeleton during interphase [51, 52] and diffuses within the cytoplasm upon cell rounding and microtubule de-polymerization (not shown).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [51] JR Bowen, 2011, Septin GTPases spatially guide microtubule organization and plus end dynamics in polarizing epithelia, The Journal of cell biology source

      Not checked in the free run.

    • cites [52] AJ Tooley, 2009, Amoeboid T lymphocytes require the septin cytoskeleton for cortical integrity and persistent motility, Nature cell biology source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Previous studies showed that cells exposed to TTFields exhibit violent plasma membrane contractions during mitosis, increased time in mitosis, and decreased cellular accumulation in exposed cultures.

    “Previous studies showed that cells exposed to TTFields exhibited violent plasma membrane contractions during mitosis, increased time in mitosis and decreased cellular accumulation in exposed cultures [38].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [38] ED Kirson, 2004, Disruption of cancer cell replication by alternating electric fields, Cancer research source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Anillin is delivered to the CCF where it normally binds to both Myosin II and Septin.

    “Anillin is delivered to the CCF where it normally binds to both Myosin II and Septin [20, 25]”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [20] CM Field, 2005, Characterization of anillin mutants reveals essential roles in septin localization and plasma membrane integrity, Development source

      Not checked in the free run.

    • cites [25] AF Straight, 2005, Anillin binds nonmuscle myosin II and regulates the contractile ring, Molecular biology of the cell source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    TTFields act by perturbing Septin localization and function during mitosis and induce mitotic catastrophe by disrupting the CCF.

    “Together these data strongly suggest a model whereby TTFields act by perturbing Septin localization and function during mitosis and induce mitotic catastrophe by disrupting the CCF (Fig 5).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Cells affected by TTFields experience aberrant mitotic exit, exhibit a G0/G1 block in cell cycle progression and apoptosis that is influenced by the cells' p53 mutational status.

    “Cells then experience aberrant mitotic exit, exhibit a G0/G1 block in cell cycle progression and apoptosis that is influenced by the cells’ p53 mutational status.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    TTFields induced cellular stress that reduced proliferation by inducing a block in G1 that was influenced by the p53 status of the cell.

    “These results demonstrate that TTFields induced cellular stress that reduced proliferation by inducing a block in G1 that was influenced by the p53 status of the cell.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    Data in Fig 3H was accumulated from three separate experiments.

    “Data was accumulated from three separate experiments (H).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Previous studies showed that TTFields perturbed cells in mitosis resulting in plasma membrane contractions and the formation of dynamic blebs on the cell surface.

    “Previous studies showed that TTFields perturbed cells in mitosis resulting in plasma membrane contractions and the formation of dynamic blebs on the cell surface. [38, 43].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [38] ED Kirson, 2004, Disruption of cancer cell replication by alternating electric fields, Cancer research source

      Not checked in the free run.

    • cites [43] ED Kirson, 2007, Alternating electric fields arrest cell proliferation in animal tumor models and human brain tumors, Proceedings of the National Academy of Sciences of the United States of America source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). The quote only partly states this claim.

    Study design and conductnone given

    Results in Fig 1A are representative of 4 separate experiments.

    “Results are representative of 4 separate experiments.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    Septin 7 microtubule localization scoring was performed by two independent and blinded scorers.

    “For subjective scoring of Septin 7 microtubule localization, cells stained for Septin 7 and α-tubulin were assigned a subjective value based on association of Septin 7 with microtubules (scored as 3) vs diffuse within the cytoplasm (scored as 1) with intermediate cells being scored as 2 by two independent and blinded scorers.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Septin becomes diffused within the cytoplasm upon suspension by trypsinization as microtubules depolymerize and becomes re-associated with them along with their re-formation upon cell spreading.

    “Septin becomes diffused within the cytoplasm upon suspension by trypsinization as microtubules depolymerize and becomes re-associated with them along with their re-formation upon cell spreading [51].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [51] JR Bowen, 2011, Septin GTPases spatially guide microtubule organization and plus end dynamics in polarizing epithelia, The Journal of cell biology source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Septins are responsible for the organization of F-actin within the CCF and bundle F-actin in the submembranous cellular cortex, which is necessary to drive successful cellular division.

    “Septins are responsible for the organization of F-actin within the CCF and bundles F-actin [53] as found in the submembranous cellular cortex which are necessary to drive successful cellular division.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [53] M Kinoshita, 2002, Self- and actin-templated assembly of Mammalian septins, Developmental cell source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    TTFields affect mitosis by directly perturbing the mitotic function of the septin complex, leading to disruption of the anaphase spindle midline structure and CCF function.

    “these data provide strong support to the likelihood that TTFields affect mitosis by directly perturbing the mitotic function of the septin complex leading to the disruption of the anaphase spindle midline structure and CCF function.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Failure to properly localize septin during mitosis is predicted to result in loss of F-actin accumulation at midline and mitotic failure.

    “Therefore the failure to properly localize septin during mitosis would be predicted to result in loss of F-actin accumlation at midline and result in mitotic failure.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Septin binds to Anillin and is important for its function during mitosis.

    “Septin binds to Anillin and is important for its function during mitosis [20].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [20] CM Field, 2005, Characterization of anillin mutants reveals essential roles in septin localization and plasma membrane integrity, Development source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The anaphase spindle midline determines both the localization of the CCF and spatially controls the activation of non-muscle myosin II that is responsible for driving ingression during anaphase.

    “The anaphase spindle midline determines both the localization of the CCF and spatially control the activation of non-muscle myosin II that is responsible for driving ingression during anaphase [18].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [18] BA Wolfe, 2009, Polo-like kinase 1 directs assembly of the HsCyk-4 RhoGAP/Ect2 RhoGEF complex to initiate cleavage furrow formation, PLoS biology source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Septins form short filaments that self-assemble into parallel arrays which are non-polar in nature.

    “Septins form short filaments that self-assemble into parallel arrays which are non-polar in nature [50, 57, 58].”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [50] M Sirajuddin, 2007, Structural insight into filament formation by mammalian septins, Nature source

      Not checked in the free run.

    • cites [57] A Bertin, 2012, Three-dimensional ultrastructure of the septin filament network in Saccharomyces cerevisiae, Molecular biology of the cell source

      Not checked in the free run.

    • cites [58] BS DeMay, 2011, Septin filaments exhibit a dynamic, paired organization that is conserved from yeast to mammals, The Journal of cell biology source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    ECT2 and Anillin cooperate to stabilize microtubules within the anaphase spindle.

    “ECT2 and Anillin cooperate to stabilize its microtubules within the anaphase spindle [21]”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [21] P Frenette, 2012, An anillin-Ect2 complex stabilizes central spindle microtubules at the cortex during cytokinesis, PloS one source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    TTFields affect cell division by interfering with CCF function and at least one key protein, Septin, involved in this process fails to properly localize to the midline of the anaphase spindle where its binding partners have been shown to be essential for promoting its stability.

    “Together, our observations demonstrate that TTFields affect cell division by interfering with CCF function and that at least one key protein, Septin, involved in this process fails to properly localize to the midline of the anaphase spindle where its binding partners have been shown to be essential for promoting its stability.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    MAP-4 is responsible for recruiting the Septin complex to the interphase microtubule cytoskeleton.

    “MAP-4 is responsible for recruiting the Septin complex to the interphase microtubule cytoskeleton [54].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [54] R Ghossoub, 2013, Septins 2, 7 and 9 and MAP4 colocalize along the axoneme in the primary cilium and control ciliary length, Journal of cell science source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

    Interpretationreasoning

    Since TTFields affect cells subsequent to both the G2/M and spindle assembly checkpoints, this adds to the unique nature of TTFields when applied in the clinic and may dictate their use with other therapies in the clinic.

    “It is important to note that since TTFields affect cells subsequent to both the G2/M and spindle assembly check points; this adds to the unique nature of TTFields when applied in the clinic and may dictate their use with other therapies in the clinic.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    This results in plasma membrane instability and blebbing that disrupts cytokinesis leading to aberrant mitotic exit and the production of deranged cells that subsequently undergo apoptosis.

    “This results in plasma membrane instability and blebbing that disrupts cytokinesis leading to aberrant mitotic exit and the production of deranged cells that subsequently undergo apoptosis (Fig 5).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Anillin is required for Septin localization to mitotic structures.

    “whereas Anillin is required for Septin localization to mitotic structures [20]”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [20] CM Field, 2005, Characterization of anillin mutants reveals essential roles in septin localization and plasma membrane integrity, Development source

      Not checked in the free run.

44 of 44

  • The authors state this as an assumption.

    TTFields exert rotational and/or torsional stress on proteins with high dipole moments.

    “The specific action of the TTFields within cells relies on their ability to exert rotational and/or torsional stress on a protein or multiple proteins with high dipole moments.”

  • The paper relies on this without support.

    Aberrant mitotic exit leads to a p53-dependent G0/1 cell cycle arrest leading to apoptosis.

    “Finally, it has been found that aberrant mitotic exit leads to a p53-dependent G0/1 cell cycle arrest leading to apoptosis.”

  • The paper relies on this without support.

    Septin heterotrimers dimerize into a longer hexamer mediated by end-to-end interactions between the Septin 2 subunits within each trimer subunit.

    “Additionally, these heterotrimers further dimerize into a longer hexamer mediated by end to end interactions between the Septin 2 subunits within each trimer subunit.”

  • The paper relies on this without support.

    The α/β-tubulin dimer possesses a significantly high dipole moment of 1660 D.

    “For example, the α/β-tubulin dimer, which acts as the functional unit of microtubule polymerization, also possesses a significantly high dipole moment of 1660 D.”
4 of 4

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Conflicting TTFields exposure durations for the post-treatment cell counts

    Major

    The cell-counting method says cells were treated for 16 hours during mitosis, whereas the results describe an 8-hour M-phase treatment for the proliferation analysis.

  • Post-treatment cell-count time points disagree

    Minor

    The methods specify counts at 4 and 20 hours after treatment, but the Fig 4 caption specifies 4 and 24 hours.

  • Annexin V measurement times use conflicting starting points

    Minor

    The Fig 4 caption measures 18, 36, and 60 hours from the midpoint of TTFields treatment, whereas the results measure those same times from the end of treatment.

  • Score 1 is described as both diffuse and not diffuse staining

    Minor

    The methods define a Septin 7 localization score of 1 as diffuse cytoplasmic staining, while the Fig 3 caption defines it as no diffuse staining.

  • Different sample sizes reported for the protein-structure analysis

    Minor

    The same 542.66 D reference value is attributed to analyses of 14,960 and 14,609 protein structures, respectively.

5 of 5

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References 60 · Cited by 217

Authors
Gera, N., Yang, A., Holtzman, T. S., Lee, S. X., Wong, E. T., & Swanson, K. D.
Affiliations
  • Harvard University (US)
  • Beth Israel Deaconess Medical Center (US)
Corresponding author
Swanson, Kenneth D.
ORCID
Venue
PLOS ONE
Publisher
Public Library of Science (PLoS)
Published
2015-05-26
Volume
10
Issue
5
Pages
e0125269
ISSN
1932-6203 (ISSN-L)
DOI
10.1371/journal.pone.0125269
PMC
PMC4444126
OpenAlex
W1899509494
Cited by
217
References
60
Citations by year
2026: 10 · 2025: 19 · 2024: 25 · 2023: 27 · 2022: 22 · 2021: 21 · 2020: 26 · 2019: 15 · 2018: 17 · 2017: 13 · 2016: 18 · 2015: 4
FWCI
9.22
Type
journal article
Language
en
Open access
Licence
Locations
  • PLoS ONE (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Digital Access to Scholarship at Harvard (DASH) (Harvard University) (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Figshare (submittedVersion, cc-by)
Funders
  • Novocure
  • National Institutes of Health
  • National Heart, Lung, and Blood Institute (R01HL116327)
  • National Institute of Allergy and Infectious Diseases (R56AI085131)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Microtubule and mitosis dynamics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Biophysics › Electromagnetic Fields and Biological Effects
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Biotechnology › Microbial Inactivation Methods
Keywords
tumor treating fields, AC electric field, septins, SEPT2, SEPT7, mitotic exit, metaphase-anaphase transition, cleavage furrow, microtubules, membrane blebbing, p53, apoptosis, mitotic catastrophe, cell proliferation inhibition
MeSH terms
Anaphase, Chromosomes, Human, Electricity, Humans, Metaphase, Mitosis, Models, Biological, Neoplasms, Stress, Physiological, Cell Death, Protein Transport, Cell Line, Tumor, Cell Proliferation, Septins

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