Abstract 1063: Effectiveness of Tumor Treating Fields (TTFields) in combination with sorafenib for treatment of hepatocellular carcinoma in vitro and in vivo
Authors: Davidi Shiri , Shteingauz Anna , Jacobovitch Sara , Gotlib Karnit , Tempel-Brami Catherine , Munster Mijal , Zeevi Einav , Dor-On Eyal , Schneiderman Rosa S. , Voloshin Tali , Haber Adi , Giladi Moshe , Kinzel Adrian , Weinberg Uri , Palti Yoram 
Published: July 2021

Purpose/Objective(s): Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and it is one of the leading causes of related mortality worldwide. Sorafenib is an oral multikinase inhibitor that targets the Raf/MEK/ERK signaling pathway, thus inducing autophagy and blocking angiogenesis. Sorafenib is approved for advanced HCC and is the main first-line chemotherapy, yet its survival benefits are limited. Tumor Treating Fields (TTFields) therapy is an anticancer treatment that is non-invasively and locoregionally delivered to tumor bed via low intensity (1-3 V/cm), intermediate frequency (100-500 kHz), alternating electric fields. Since HCC is a complex, heterogeneous tumor with exhibited aberrant signaling pathways, sorafenib combined with additional chemotherapy agents and other types of treatment modalities, such as TTFields, may be a feasible option for targeting HCC. The purpose of this study was to explore the use of TTFields, alone and in combination with sorafenib, for HCC treatment.

Materials/Methods: HCC cell lines (HepG2 and Huh-7D12) were treated for 72 hours with TTFields at various frequencies. Efficacy of TTFields and sorafenib combination was tested by applying optimal frequency TTFields in the presence of various concentrations of sorafenib. Cytotoxicity, apoptosis, and clonogenicity were determined, and overall effect was calculated as the product of the cytotoxic and clonogenic effects. Changes in autophagy levels were also examined. In vivo, N1S1 HCC cells (50,000) were orthotopically injected into the left hepatic lobe of SD rats. After 1 week, TTFields at the optimal frequency were continuously applied for 6 days to the abdominal region of rat torsos, and sorafenib (10 mg/kg/day) was injected daily. Tumor volume growth was determined by MRI.

Results: The TTFields frequency assessed for optimally treating HCC cell lines was 150 kHz. Cells were sensitive to sorafenib in a dose-dependent manner, and concomitant addition of TTFields augmented this effect. The effect of TTFields, like that of sorafenib, was demonstrated to be related to increases in autophagic flux. In the animal model, tumor growth was significantly reduced in the combination group compared to other treatment groups.

Conclusion: These results demonstrate that TTFields are effective for the treatment of HCC and may further enhance effectiveness in combination with standard of care chemotherapy. The ongoing phase 2 HEPANOVA (NCT03606590) clinical trial will investigate the safety and efficacy of TTFields plus sorafenib combination in patients with unresectable, locally advanced HCC.

Citation Format: Shiri Davidi, Anna Shteingauz, Sara Jacobovitch, Karnit Gotlib, Catherine Tempel-Brami, Mijal Munster, Einav Zeevi, Eyal Dor-On, Rosa S. Schneiderman, Tali Voloshin, Adi Haber, Moshe Giladi, Adrian Kinzel, Uri Weinberg, Yoram Palti. Effectiveness of Tumor Treating Fields (TTFields) in combination with sorafenib for treatment of hepatocellular carcinoma in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1063.