Tumor Treating Fields (TTFields) are noninvasive, alternating electric fields within the intermediate frequency range (100–300 kHz) that are utilized as an antimitotic cancer treatment. TTFields are loco-regionally delivered to the tumor region through 2 pairs of transducer arrays placed on the skin. This novel treatment modality has been FDA-approved for use in patients with glioblastoma and malignant pleural mesothelioma based on clinical trial data demonstrating efficacy and safety; and is currently under investigation in other types of solid tumors. TTFields were shown to induce an anti-mitotic effect by exerting bi-directional forces on highly polar intracellular elements, such as tubulin and septin molecules, eliciting abnormal microtubule polymerization during spindle formation as well as aberrant cleavage furrow formation. Previous studies have demonstrated that TTFields inhibit metastatic properties in cancer cells. However, the consequences of TTFields application on cytoskeleton dynamics remain undetermined. In this study, methods utilized in combination to study the effects of TTFields on cancer cell motility through regulation of microtubule and actin dynamics included confocal microscopy, computational tools, and biochemical analyses. Mechanisms by which TTFields treatment disrupted cellular polarity were (1) interference with microtubule assembly and directionality; (2) altered regulation of Guanine nucleotide exchange factor-H1 (GEF-H1), Ras homolog family member A (RhoA), and Rho-associated coiled-coil kinase (ROCK) activity; and (3) induced formation of radial protrusions of peripheral actin filaments and focal adhesions. Overall, these data identified discrete effects of TTFields that disrupt processes crucial for cancer cell motility.

Development of protein kinase inhibitors is a focus of many drug discovery programs. A major problem, however, is the limited specificity of the commonly used adenosine triphosphate-competitive inhibitors and the weak inhibition of the more selective substrate-competitive inhibitors. Glycogen synthase kinase-3 (GSK-3) is a promising drug target for treating neurodegenerative disorders, including Alzheimer's disease (AD), but most GSK-3 inhibitors have not reached the clinic. We describe a new type of GSK-3 inhibitor, L807mts, that acts through a substrate-to-inhibitor conversion mechanism that occurs within the catalytic site of the enzyme. We determined that L807mts was a potent and highly selective GSK-3 inhibitor with reasonable pharmacological and safety properties when tested in rodents. Treatment with L807mts enhanced the clearance of β-amyloid loads, reduced inflammation, enhanced autophagic flux, and improved cognitive and social skills in the 5XFAD AD mouse model. This new modality of GSK-3 inhibition may be therapeutic in patients with AD or other central nervous system disorders associated with dysregulated GSK-3.

No abstract

Tumor Treating Fields (TTFields) are electric fields that exert physical forces to disrupt cellular processes critical for cancer cell viability and tumor progression. TTFields induce anti-mitotic effects through the disruption of the mitotic spindle and abnormal chromosome segregation, which trigger several forms of cell death, including immunogenic cell death (ICD). The efficacy of TTFields concomitant with anti-programmed death-1 (anti-PD-1) treatment was previously shown in vivo and is currently under clinical investigation. Here, the potential of TTFields concomitant with anti- PD-1/anti-cytotoxic T-lymphocyte-associated protein 4 (anti-CTLA-4) or anti-programmed death-ligand 1 (anti-PD-L1) immune checkpoint inhibitors (ICI) to improve therapeutic efficacy was examined in lung tumor-bearing mice. Increased circulating levels of high mobility group box 1 protein (HMGB1) and elevated intratumoral levels of phosphorylated eukaryotic translation initiation factor 2α (p-eIF2α) were found in the TTFields-treated mice, indicative of ICD induction. The concomitant application of TTFields and ICI led to a significant decrease in tumor volume as compared to all other groups. In addition, significant increases in the number of tumor-infiltrating immune cells, specifically cytotoxic T-cells, were observed in the TTFields plus anti-PD-1/anti-CTLA-4 or anti-PD-L1 groups. Correspondingly, cytotoxic T-cells isolated from these tumors showed higher levels of IFN-γ production. Collectively, these results suggest that TTFields have an immunoactivating role that may be leveraged for concomitant treatment with ICI to achieve better tumor control by enhancing antitumor immunity.

Introduction: Tumor Treating Fields (TTFields) are low intensity (1-3 V/cm), intermediate frequency (100-500 kHz), alternating electric fields that are delivered non-invasively to tumors. TTFields therapy is approved in the US and Europe for the treatment of patients with glioblastoma or mesothelioma. In addition to an established anti-mitotic mechanism of action, previous studies have shown that TTFields-induced cell death stimulates anti-tumor immunity and promotes the maturation of dendritic cells. In the current research, the effect of TTFields on the polarization of unstimulated macrophages and the phenotypic regulation of M1 and M2 macrophages was investigated. Methods: Bone marrow-derived macrophages (BMDMs) were generated from the femurs and tibias of 5-8-week-old Balb\C mice. TTFields (150 kHz) were applied for 24 h to unstimulated (M0 phenotype) BMDMs and BMDMs stimulated with LPS+IFN-γ (M1 polarization) or IL-4 (M2 polarization). Flow cytometry was used to identify surface expression of the macrophage biomarker F4/80 and activation markers CD80, major histocompatibility complex class II (MHC II), inducible nitric oxide synthase (iNOS), CD206, and ARG-1. Multiplexed secretion assays were conducted to quantify CXCL1 (KC), IL-18, IL-23, IL-12p70, IL6, TNF-α, IL-12p40, free active TGF-β1, CCL22 (MDC), IL-10, IL-6, G-CSF, CCL17 (TARC), and IL-1β as to examine the heterogeneity of the stimulated macrophages. Results: The percentage of cells expressing the pro-inflammatory M1 markers CD80+ and MHC IIhigh was significantly increased following application of TTFields to polarized (M1 or M2) or unpolarized BMDMs, while expression of the M2 markers CD206 and ARG-1 was significantly decreased. A pro-inflammatory secretion pattern, with increased levels of CXCL1, IL-18, IL-23, IL-12p70, TNF-α, IL-12p40, CCL22, G-CSF, CCL17 and IL-1β was observed in cell supernatants of M1 and M2 stimulated BMDMs, and unstimulated M0 BMDMs, following delivery of TTFields. Taken together, TTFields polarized unstimulated BMDMs to the M1 phenotype, and induced phenotype skewing of M2 polarized BMDMs to the M1 phenotype. Conclusions: TTFields therapy displays a novel immunoregulatory role in macrophage polarization and promotes a pro-inflammatory phenotype. Future investigations will focus on defining the underlying mechanism of this phenotypic skewing. Citation Format: Yiftah Barsheshet, Boris Brant, Tali Voloshin, Alexandra Volodin, Lilach Koren, Bella Koltun, Anat Klein-Goldberg, Efrat Zemer-Tov, Tal Kan, Rom Paz, Moshe Giladi, Uri Weinberg, Yoram Palti. Tumor Treating Fields (TTFields) promote a pro-inflammatory phenotype in macrophages [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1305.