HIF-1a blockade enhances the therapeutic efficacy of hypoxia for the treatment of hepatocellular carcinoma (HCC)

Abstract

Background and objective: Transarterial embolization (TAE) is the major alternative for the treatment of non-resectable HCC. Although the hypoxic condition generated by hepatic artery blockade could induce tumor cell death, hypoxia-related angiogenesis and subsequent tumor re-growth might lead to treatment failure. Therefore, we designed the present study to investigate whether suppression of the activity of HIF- 1a, a key player in angiogenesis, could enhance the therapeutic efficacy of hypoxia. Materials and methods: In vivo, an orthotopic HCC model was generated by injection of tumor cells into the left lobe of the rat liver. Hypoxia was induced by hepatic artery ligation (HAL). YC-1, an anti-HIF-1a agent, was administered through intra-tumor injection right after hepatic artery ligation. Survival time was recorded and the histology of tumor tissue was studied. In vitro, hypoxia was induced by culturing the cells with 0.1% O2. YC-1 was administered to the tumor cells at different concentrations under hypoxic condition. The proliferation and death of the cells were determined by MTT assay and Annexin-V labeling, respectively. Molecular mechanism related to HIF-1a was determined by Western blot. Results: HAL stimulated HIF-1a upregulation in the tumor tissue with a peak level at 24 h. Administration of YC-1 significantly prolonged the survival of tumor-bearing rats. Both HAL and HAL combined with YC-1 induced tumor tissue necrosis. YC-1 administration decreased the number of HIF-1a+ cells in the tumor tissue. In the HCC tumor cells, YC-1 administration decreased the viability of tumor cells but did not cause any change in the number of apoptotic cells. Hypoxia upregulated the expression of HIF- 1a, that could be suppressed by YC-1 administration. In addition, YC-1 could inhibit HIF-1a expression despite the presence or absence of p53 in the tumor cell lines. However, the suppressive effect of YC-1 on HIF- 1a could be blocked by the transfection of MDM2, a downstream molecule of p53. Conclusion: The present study revealed that blockade of HIF-1a-related pathway could enhance the efficacy of hypoxia for the treatment of HCC. YC-1 achieved anti-HIF-1a effects through p53 independent and MDM2 dependent pathways.