Tumor Treating Fields (TTFields) Concomitant with Sorafenib Inhibit Hepatocellular Carcinoma In Vitro and In Vivo

SIMPLE SUMMARY: Hepatocellular carcinoma (HCC), an advanced liver cancer, has poor prognosis and limited treatment options. Tumor Treating Fields (TTFields) therapy is a novel antimitotic treatment, delivering electric fields that induce death and inhibit replication of cancer cells. We aimed to determine the effect of TTFields in HCC cells and an animal model, alone or in combination with sorafenib, an approved HCC treatment option. Human HCC cells were treated with TTFields at various frequencies to identify the most effective frequency. TTFields at 150 kHz were shown to induce anti-cancerous effects and to amplify such effects displayed by sorafenib. In animals, TTFields concomitant with sorafenib were more effective than either TTFields or sorafenib alone in reducing tumor volume, with the combination also leading to more cases of stable disease. Overall, this research demonstrates potential for concomitant TTFields and sorafenib application in the treatment of HCC. ABSTRACT: Hepatocellular carcinoma (HCC), a highly aggressive liver cancer, is a leading cause of cancer-related death. Tumor Treating Fields (TTFields) are electric fields that exert antimitotic effects on cancerous cells. The aims of the current research were to test the efficacy of TTFields in HCC, explore the underlying mechanisms, and investigate the possible combination of TTFields with sorafenib, one of the few front-line treatments for patients with advanced HCC. HepG2 and Huh-7D12 human HCC cell lines were treated with TTFields at various frequencies to determine the optimal frequency eliciting maximal cell count reduction. Clonogenic, apoptotic effects, and autophagy induction were measured. The efficacy of TTFields alone and with concomitant sorafenib was tested in cell cultures and in an orthotopic N1S1 rat model. Tumor volume was examined at the beginning and following 5 days of treatment. At study cessation, tumors were weighed and examined by immunohistochemistry to assess autophagy and apoptosis. TTFields were found in vitro to exert maximal effect at 150 kHz, reducing cell count and colony formation, increasing apoptosis and autophagy, and augmenting the effects of sorafenib. In animals, TTFields concomitant with sorafenib reduced tumor weight and volume fold change, and increased cases of stable disease following treatment versus TTFields or sorafenib alone. While each treatment alone elevated levels of autophagy relative to control, TTFields concomitant with sorafenib induced a significant increase versus control in tumor ER stress and apoptosis levels, demonstrating increased stress under the multimodal treatment. Overall, TTFields treatment demonstrated efficacy and enhanced the effects of sorafenib for the treatment of HCC in vitro and in vivo, via a mechanism involving induction of autophagy.