STAT3 inhibition reduces toxicity of oncolytic VSV and provides a potentially synergistic combination therapy for hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a refractory malignancy with a high mortality and increasing worldwide incidence rates, including the United States and central Europe. In this study, we demonstrate that a specific inhibitor of signal transducer and activator of transcription 3 (STAT3), NSC74859, efficiently reduces HCC cell proliferation and can be successfully combined with oncolytic virotherapy using vesicular stomatitis virus (VSV). The potential benefits of this combination treatment are strengthened by the ability of NSC74859 to protect primary hepatocytes and nervous system cells against virus-induced cytotoxicity, with an elevation of the VSV maximum tolerated dose in mice. Hereby we propose a strategy for improving the current regimen for HCC treatment and seek to further explore the molecular mechanisms underlying selective oncolytic specificity of VSV.

JNK inhibition sensitises hepatocellular carcinoma cells but not normal hepatocytes to the TNF-related apoptosis-inducing ligand.

BACKGROUND: cJun terminal kinase (JNK) is constitutively activated in most hepatocellular carcinomas (HCCs), yet its exact role in carcinogenesis remains controversial. While tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is known as a major mediator of acquired immune tumour surveillance, and is currently being tested in clinical trials as a novel cancer therapy, the resistance of many tumours to TRAIL and concerns about its toxicity in vivo represent obstacles to its clinical application. In this study we investigated whether JNK activity in HCC could contribute to the resistance to apoptosis in these tumours. METHODS: The effect of JNK/Jun inhibition on receptor-mediated apoptosis was analysed by pharmacological inhibition or RNA interference in cancer cells and non-tumour cells isolated from human liver or transgenic mice lacking a phosphorylation site for Jun. RESULTS: JNK inhibition caused cell cycle arrest, enhanced caspase recruitment, and greatly sensitised HCC cells but not normal hepatocytes to TRAIL. TRAIL-induced activation of JNK could be effectively interrupted by administration of the JNK inhibitor SP600125. CONCLUSIONS: Expression and TRAIL-dependent feedback activation of JNK likely represent a mechanism by which cancer cells escape TRAIL-mediated tumour surveillance. JNK inhibition might represent a novel strategy for specifically sensitising HCC cells to TRAIL thus opening promising therapeutic perspectives for safe and effective use of TRAIL in cancer treatment.