Directionally non-rotating electric field therapy (dnEFT) delivered through implanted electrodes as a glioblastoma treatment platform: a proof-of-principle study

Abstract

While directionally rotating Tumor Treating Fields (TTF) therapy has garnered considerable clinical interest in recent years, there has been comparatively less focus on directionally non-rotating electric field therapy (dnEFT). We explored dnEFT generated through customized electrodes as a glioblastoma therapy in in vitro and in vivo pre-clinical models. The effects of dnEFT on tumor apoptosis and microglia/macrophages in the tumor microenvironment were tested using flow-cytometric and qPCR assays. In vitro, dnEFT generated using a clinical grade spinal cord stimulator showed anti-neoplastic activity against independent glioblastoma cell lines. In support of the results obtained using the clinical grade electrode, dnEFT delivered through a customized, two-electrode array induced glioblastoma apoptosis. To characterize this effect in vivo, a custom-designed four-electrode array was fabricated such that tumor cells can be implanted into murine cerebrum through a center channel equidistant from the electrodes. After implantation with this array and luciferase expressing murine GL261 glioblastoma cells, mice were randomized to dnEFT or placebo. Relative to placebo treated mice, dnEFT reduced tumor growth (measured by bioluminescence) and prolonged survival (median survival gain of 6.5 days). Analysis of brain sections following dnEFT showed a notable increase in the accumulation of peri-tumoral macrophage/microglia with increased expression of M1 genes (IFNγ, TNFα, IL-6) and decreased expression of M2 genes (CD206, Arg, IL-10) relative to placebo treated tumors. Our results suggest therapeutic potential in glioblastoma for dnEFT delivered through implanted electrodes, supporting the development of a proof-of-principle clinical trial using commercially available deep brain stimulator electrodes.