Overexpression of von Hippel-Lindau protein synergizes with doxorubicin to suppress hepatocellular carcinoma in mice

Background 82 Aims: Hypoxia-inducible factors (HIFs) and nuclear factor-kappa B (NF-kappa B) regulate genes involved in carcinogenesis and progression of cancers including hepatocellular carcinoma (HCC). The von Hippel Lindau (VHL) protein (pVHL) targets HIF alpha subunits for destruction and participates in modulating the activity of NF-kappa B. The present study aimed to investigate whether the overexpression of pVHL synergizes with doxorubicin in the treatment of HCC. Methods: Overexpression of pVHL was induced by infecting mouse HCC Nepal 6 and H22 cells, or injecting subcutaneous Hepa1-6 tumors in C57BL/c mice, with adenoviral vectors encoding mouse VHL gene. Cell proliferation, apoptosis, tumoral angiogenesis, and gene expression and DNA-binding activity of NF-kappa B were examined. The therapeutic effects of pVHL were also evaluated in orthotopic Hepa1-6 tumors by intraportal delivery of Ad-VHL. Results: Ad-VHL enhanced the anti-tumor activity of doxorubicin by inhibiting cell proliferation, and causing cell cycle arrest and apoptosis. The Ad-VHL infection downregulated HIF-1 alpha and HIF-2 alpha expression, and inhibited NF-kappa B activity and the expression of genes involved in apoptosis, proliferation, angiogenesis, invasion, and metastasis. Injection of Ad-VHL into HCC tumors augmented doxorubicin-induced suppression of tumor growth by inhibiting cell proliferation and tumor angiogenesis, and by inducing cell apoptosis. Effects on the expression of HIF alpha s, activity of NF-kappa B, and their downstream genes were in accordance with the in vitro findings. Intraportal injection of Ad-VHL enhanced the efficacy of doxorubicin to suppress the growth of orthotopic liver tumors. Conclusions: By targeting HIF and NF-kappa B, overexpression of pVHL enhances the efficacy of doxorubicin, and warrants consideration as a potential therapeutic strategy for treating HCC. (C) 2010 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.