Moderate Heat Application Enhances the Efficacy of Nanosecond Pulse Stimulation for the Treatment of Squamous Cell Carcinoma

Abstract

Nanosecond pulse stimulation as a tumor ablation therapy has been studied for the treatment of various carcinomas in animal models and has shown a significant survival benefit. In the current study, we found that moderate heating at 43°C for 2 minutes significantly enhanced in vitro nanosecond pulse stimulation-induced cell death of KLN205 murine squamous cell carcinoma cells by 2.43-fold at 600 V and by 2.32-fold at 900 V, as evidenced by propidium iodide uptake. Furthermore, the ablation zone in KLN205 cells placed in a 3-dimensional cell-culture model and pulsed at a voltage of 900 V at 43°C was 3 times larger than in cells exposed to nanosecond pulse stimulation at room temperature. Application of moderate heating alone did not cause cell death. A nanosecond pulse stimulation electrode with integrated controllable laser heating was developed to treat murine ectopic squamous cell carcinoma. With this innovative system, we were able to quickly heat and maintain the temperature of the target tumor at 43°C during nanosecond pulse stimulation. Nanosecond pulse stimulation with moderate heating was shown to significantly extend overall survival, delay tumor growth, and achieve a high rate of complete tumor regression. Moderate heating extended survival nearly 3-fold where median overall survival was 22 days for 9.8 kV without moderate heating and over 63 days for tumors pulsed with 600, 100 ns pulses at 5 Hz, at voltage of 9.8 kV with moderate heating. Median overall survival in the control groups was 24 and 31 days for mice with untreated tumors and tumors receiving moderate heat alone, respectively. Nearly 69% (11 of 16) of tumor-bearing mice treated with nanosecond pulse stimulation with moderate heating were tumor free at the completion of the study, whereas complete tumor regression was not observed in the control groups and in 9.8 kV without moderate heating. These results suggest moderate heating can reduce the necessary applied voltage for tumor ablation with nanosecond pulse stimulation.

Thermal Analysis of Infrared Irradiation-Assisted Nanosecond-Pulsed Tumor Ablation

“…Similar results have been shown using the 4-needle electrode orientation and laser heating with microsecond pulses using Pan02 pancreatic cancer cells, suggesting that the addition of heat to PEF treatments have beneficial effects 17,28 . Moreover, our previous numerical analyses of electric field distribution in similar electrode configurations support that preheating tumor was able to greatly reduce the threshold of electric field strength for tumor ablation 29 . The use of a range of electric parameters and the requirement for different electric field strengths for in vitro 3D and in vivo pancreatic tumor models to achieve comparable results were reported previously 17 .…”

Moderate Heat-Assisted Gene Electrotransfer as a Potential Delivery Approach for Protein Replacement Therapy through the Skin

“…When the application of moderate heating and electric field is combined, these effects are more pronounced and delivery is more efficient. Moderate heating is also advantageous in the context of irreversible elec troporation, where the applied heat sensitizes cancer cells to the applied electric field, thus making a more effective treatment [48,67,68].…”

The First Application of Nanoelectrochemotherapy in Feline Oral Malignant Melanoma Treatment—Case Study

“…We used 200 Hz frequency (200 pulses/second), but the total energy of the burst was more than 60-fold lower, which allowed us to ensure a nonthermal treatment. In the other studies authors were able to maintain constant temperature (43 • C) during the nanosecond procedure [19]. Currently nsPEF clinical trials are not widespread.…”