Tumor treating fields effects on the blood-brain barrier in vitro and in vivo

2551

Background: The greatest hurdle, which even potent and effective drugs targeting central nervous system (CNS) tumors and other disorders face, is the blood brain barrier (BBB). The inability to cross the tight regulatory mechanism renders these drugs futile. Of late, administration of tumor treating fields (TTFields) as part of a combined treatment modality for glioblastoma demonstrated increased overall patient survival. Still, the effects of TTFields on the BBB have not yet been investigated. Here, we report the potential of TTFields application to open up the BBB. Methods: Murine brain endothelial cells were treated with 100-300 kHz TTFields for 24-96 h. Cells were also allowed to recover from 24-96 h after treatment. Subsequently, changes in cell morphology, integrity, and permeability were observed via staining of intercellular junction proteins (IJP) as well as transendothelial electrical resistance (TEER)and permeability assays. In vivo, rats were treated with 100 kHz TTFields or heat for 72 h after which they were IV injected with Evan´s Blue (EB)/ TRITC-dextran (TD) which was later quantified from the brain. Rat brain cryosections were also stained for IJPs as well as immunoglobulin G (IgG) to assess vessel structure. Finally, serial dynamic contrast-enhanced (DCE) MRI with gadolinium (Gd) contrast agent was performed pre- and post- TTFields. Results: Upon TTFields application, IJPs such as claudin-5 were delocalized from the cell membrane to the cytoplasm with maximal effects at 100 kHz. In addition, BBB integrity was significantly reduced and permeability for 4 kDa molecules was significantly increased. Cell morphology recovery was first observed at 48 h post-treatment and completely restored to normal after 96 h, indicating a reversibility of the TTFields effect on the BBB. In addition, EB and TD permeated the rat brain post-TTFields treatment. Brain cryosections displayed IJPs delocalization as well as IgG accumulation in the brain parenchyma. Confirming these observations, increased Gd in the brain was shown by DCE-MRI post-TTFields application. A reversion to normal conditions was detected 96 h after end of treatment, which was demonstrated by no difference in contrast enhancement between control and treated rats. Conclusions: TTFields application both in vitro and in vivo points towards its ability to transiently open the BBB. This presents TTFields as a novel aid for drug delivery geared towards treatment of CNS tumors and other related diseases. Hence, it is indicative of the possibility of an enhanced and more effective combinatorial therapeutic strategy.

The combined treatment of 150 kHz tumor treating fields (TTFields) and sorafenib inhibits hepatocellular carcinoma in vitro and in vivo

e15653

Background: Hepatocellular carcinoma (HCC) is the third cause of cancer related mortality and the primary cause of cancer death. Tumor Treating Fields (TTFields) therapy is an effective anti-neoplastic treatment modality delivered via noninvasive application of low intensity, intermediate frequency, alternating electric fields. Sorafenib, an oral multikinase inhibitor is approved for patients with advanced HCC, yet its survival benefit is still limited. In this work we explored the potential of the use of TTFields alone and in combination with Sorafenib as a treatment for HCC. Methods: HepG2 and Huh-7D12 cells were treated with various TTFields frequencies for 72 hours using the inovitro system. Efficacy of the combined treatment of TTFields and Sorafenib (36-3000 nM) was tested by applying TTFields at the optimal frequency together with various drug concentrations. Cell counts, induction of apoptosis, cell cycle and clonogenic potential were determined. TTFields (1.2 V/cm) and Sorafenib (10 mg/kg) were applied for 6 days to rats injected to the liver with N1S1 HCC cells. Tumor growth was followed using MRI. Results: The optimal TTFields frequency was 150 kHz for both cell lines. TTFields application (1.0 - 1.7 V/cm, 72 hours) at 150 kHz led to 36-40% reduction in cell counts and to additional reduction of over 70% in the clonogenic potential. The combined treatment of TTFields and Sorafenib led to a significant reduction in the number of cells (p < 0.001) as compared to each treatment alone. The averaged tumor volume fold increase of the combination treatment group was significantly lower than the one observed in the: control group, the TTFields group and the Sorafenib group. Conclusions: The results presented in this work demonstrate that TTFields can be an effective treatment against HCC cells and that the combination with Sorafenib may further enhance treatment efficacy.

In vitro and in vivo efficacy of the combined treatment of 150 khz tumor treating fields (TTFields) and sorafenib in hepatocellular carcinoma

333

Background: Hepatocellular carcinoma (HCC) is the third cause of cancer related mortality and the primary cause of cancer death. Sorafenib, an oral multikinase inhibitor is approved for patients with advanced HCC, yet its survival benefit is still limited. Tumor Treating Fields (TTFields) therapy is an effective anti-neoplastic treatment modality delivered via noninvasive application of low intensity, intermediate frequency, alternating electric fields. The aim of this work is to explore the potential of the use of TTFields alone and in combination with Sorafenib as a treatment for HCC. Methods: HepG2 and Huh-7D12 cells were treated with various TTFields frequencies for 72 hours using the inovitro system. Efficacy of the combined treatment of TTFields and Sorafenib (36-3000 nM) was tested by applying TTFields at the optimal frequency together with various drug concentrations. Cell counts, induction of apoptosis, cell cycle and clonogenic potential were determined. N1S1 HCC cells were injected to the left lobe of the liver of SD rats. After 1 week, TTFields (1.2 V/cm) and Sorafenib (10 mg/kg) were applied for 6 days and tumor growth was followed using MRI. Healthy rats were used to study safety of the use of TTFields (150 kHz) applied to the abdomen. Results: The optimal TTFields frequency was found to be 150 kHz for both cell lines. TTFields application (1.0 - 1.7 V/cm, 72 hours) at 150 kHz led to 53-64% reduction in cell counts and to additional reduction of over 70% in the clonogenic potential. The combined treatment of TTFields and Sorafenib led to a significant reduction in the number cells (2-way ANOVA, p < 0.001) as compared to each treatment alone. Tumor growth was significantly reduced by the combined group compared to the control group (student t test, p < 0.01). Safety studies did not reveal any adverse event associated with TTFields application to the rat abdomen. Conclusions: The results presented in this work demonstrate that TTFields can be a safe and effective treatment against HCC cells and that the combination with Sorafenib may further enhance treatment efficacy.