Characterization of Ablation Thresholds for 3D-Cultured Patient-Derived Glioma Stem Cells in Response to High-Frequency Irreversible Electroporation

Abstract

<jats:p>High-frequency irreversible electroporation (H-FIRE) is a technique that uses pulsed electric fields that have been shown to ablate malignant cells. In order to evaluate the clinical potential of H-FIRE to treat glioblastoma (GBM), a primary brain tumor, we have studied the effects of high-frequency waveforms on therapy-resistant glioma stem-like cell (GSC) populations. We demonstrate that patient-derived GSCs are more susceptible to H-FIRE damage than primary normal astrocytes. This selectivity presents an opportunity for a degree of malignant cell targeting as bulk tumor cells and tumor stem cells are seen to exhibit similar lethal electric field thresholds, significantly lower than that of healthy astrocytes. However, neural stem cell (NSC) populations also exhibit a similar sensitivity to these pulses. This observation may suggest that different considerations be taken when applying these therapies in younger versus older patients, where the importance of preserving NSC populations may impose different restrictions on use. We also demonstrate variability in threshold among the three patient-derived GSC lines studied, suggesting the need for personalized cell-specific characterization in the development of potential clinical procedures. Future work may provide further useful insights regarding this patient-dependent variability observed that could inform targeted and personalized treatment.</jats:p>

Microsecond Pulsed Electric Fields: An Effective Way to Selectively Target and Radiosensitize Medulloblastoma Cancer Stem Cells

“…Similar behavior for NHAs exposed to a different msPEF protocol has been reported in previous studies, 33,34 in comparison with glioblastoma cancer stem-like cells. In these studies, the role of cell dimension and aspect ratio between the cell nucleus and the cytoplasm diameters in regulating msPEF's selective action on the glioblastoma CSCs were hypothesized and assessed.…”

“…In our investigation, the selective action of msPEF on MB cells seems to not depend on cell dimension and aspect ratio, as opposed to what has been reported elsewhere. 34 The more sensitive D283 cells are much smaller (diameter of about 10 mm) than NHAs (diameter of about 20 mm). This result is also in contrast to what is usually believed in electroporation theories and models, 35 suggesting that bigger cells should be electropermeabilized more easily than smaller ones, hence presenting a higher electroporation threshold.…”

“…They also appear to be the reason why conventional therapies fail (ie, chemotherapy and radiation therapy) and the cause of cancer relapse and metastasis. [15][16][17] Electrically mediated therapies are good candidates for new therapeutic strategies to specifically target CSCs, 33,34 as well as to reduce or eliminate side effects associated with conventional therapies, although studies on this topic are still scarce.…”

Temporal Characterization of Blood–Brain Barrier Disruption with High-Frequency Electroporation

“…To counteract the effects of HFE on excitable tissues like muscle and nerves, higher frequency waveforms, or shorter pulse durations (<2 µs), could be used as opposed to 5 µs pulses [47]; as previously demonstrated, longer pulse durations typical of IRE (100 µs) are more likely to induce muscle/nerve excitation [32]. On the contrary, shorter pulse durations require a higher voltage to achieve a similar ablation in healthy tissue if the other pulsing parameters are maintained; in malignant cells, H-FIRE selectivity seems to benefit from using higher frequency waveforms [38,[48][49][50]. The relationship between pulse width, cell kill, and tissue excitation has been modestly investigated [34,51], so future efforts to find the optimal pulsing parameters may prove beneficial for H-FIRE therapy.…”

The feasibility of using dielectrophoresis for isolation of glioblastoma subpopulations with increased stemness

“…GSCs reside in the perivascular and hypoxic niches of glioblastoma tumors and exhibit plasticity, self‐renewal properties, resistance to therapies, and ability to cause relapse . Hence, it is important to characterize properties of GSCs with the goal of finding therapies that target this subpopulation . Separation of GSCs has been challenging and has led to discrepancies in the field of cancer stem cells (CSCs).…”