Programa del congreso

It has been shown that the continuous delivery of low-magnitude (1–3 V/cm) alternating electric fields of moderate frequency (100–300 kHz) hinders cell proliferation [1]. In particular, these fields, referred to as Tumor Treating Fields (TTFs), have demonstrated clinical efficacy against glioblastoma, slowing disease progression when combined with chemotherapy. The mechanism of action of TTFs has long been proposed to involve dielectrophoretic forces that disrupt tubulin polymerization, thereby arresting cells in mitosis. However, this hypothesis has been challenged [2]. We hypothesize that, instead, their mechanism of action is mediated by electroporation.

Because electroporation outcomes depend more on electric field amplitude than on exposure duration [3], we propose that delivering slightly stronger—but still mild—fields in short AC bursts, which we term Tumor Treatment Alternating Currents (TTACs), may inhibit proliferation more effectively than conventional continuous TTFs while maintaining thermal safety.

1. Materials and Methods

U87 human glioblastoma cells were cultured and treated in rectangular chambers with platinum electrodes at opposite ends. TTF exposure consisted of a continuous sinusoidal field of 2 V/cm and 200 kHz. TTACs were generated as sinusoidal bursts using a function generator and high‑voltage amplifier. Importantly, TTACs and TTFs were matched for Specific Absorption Rate (SAR = 30 W/kg) to equalize energy deposition.

Phase‑contrast images of fixed fields of view were acquired immediately before initiating treatment, that is, 24 hours after seeding cells (day 1), and 48 h later (day 3). Cells were segmented with Cellpose, a generalist deep learning–based algorithm for cellular segmentation, and a Proliferation Index was computed as the percent change from Day 1 to Day 3. Data from six independent repetitions were collected and analyzed statistically. Group differences were assessed with a Kruskal–Wallis test followed by pairwise two‑sided Mann–Whitney U tests.

2. Results

Across a 48-h window, the Proliferation Index (percent change from day 1 to day 3) differed among groups (Kruskal–Wallis p = 1.63 × 10⁻⁶) (Figure 1). Both treatments reduced proliferation relative to Control: TTAC showed the largest reduction (median 107% [IQR 52–129]), TTF a moderate reduction (median 133% [IQR 126–141]), versus Control (median 161% [IQR 140–178]). Pairwise Mann–Whitney U tests confirmed lower proliferation for **TTAC vs Control (p = 4.2 × 10⁻⁶, **) and **TTF vs Control (p = 9.34 × 10⁻⁴, *), and indicated a difference between TTAC and TTF (p = 1.85 × 10⁻², *). Collectively, both exposures suppressed 48-h proliferation versus Control, with TTAC exerting the stronger effect.

Figure 1. 48‑h Proliferation Index (median and IQR) for Control, TTAC (i.e., pulsed alternating field therapy), and TTF (i.e., continuous alternating electric field therapy).

3. Conclusions

In these 72 hours in vitro assays, pulsed alternating fields of higher magnitude but with the same eneregy as conventional TTFs produced stronger antiproliferative effects in U87 cells. These preliminary results suggest that delivering prolonged, mild-intensity electric fields in short bursts may be more effective than continuous TTFs at inhibiting cell proliferation, highlighting a potential strategy for cancer therapy.

References

[1] E. D. Kirson et al., ‘Disruption of Cancer Cell Replication by Alternating Electric Fields’, Cancer Research, vol. 64, no. 9, pp. 3288–3295, May 2004, doi: 10.1158/0008-5472.CAN-04-0083.

[2] X. Li, K. Liu, H. Fang, Z. Liu, Y. Tang, and P. Dai, ‘Electrodynamic interaction between tumor treating fields and microtubule electrophysiological activities’, APL Bioengineering, vol. 8, no. 2, p. 026118, Jun. 2024, doi: 10.1063/5.0197900.

[3] S. N. Campelo, P.-H. Huang, C. R. Buie, and R. V. Davalos, ‘Recent Advancements in Electroporation Technologies: From Bench to Clinic’, Annu. Rev. Biomed. Eng., vol. 25, no. 1, pp. 77–100, Jun. 2023, doi: 10.1146/annurev-bioeng-110220-023800.