Blockade of vascular endothelial growth factor (VEGF) receptor enhances the therapeutic efficacy of hypoxia and chemotherapy in hepatocellular carcinoma

Abstract

Background: Transcatheter arterial chemoembolization (TACE) is a widely used approach for the treatment of hepatocellular carcinoma (HCC) of an advanced stage. However, long-term survival of patients is not satisfactory. Our previous study revealed that some hypoxia-related molecules, such as hypoxia-inducible factor 1α and VEGF, were upregulated after hepatic artery ligation and led to treatment failure (Cancer Research 2004). The present study is designed to investigate the combined therapeutic efficacy of VEGF receptor blockade with hypoxia and chemotherapy in HCC. Materials and Methods: An orthotopic HCC model was generated by injection of rat McA RH7777 HCC cells into the left lobe of the liver. Ten days after tumor cell inoculation, the animals received the following treatments: 1) sham operation; 2) cisplatin 3 mg/kg intraportal vein injection; 3) hepatic artery ligation; 4) hepatic artery ligation combined with cisplatin; 5) PTK 787 (VEGF receptor blocker) 50 mg/kg oral feeding daily; 6) cisplatin combined with PTK 787; 7) hepatic artery ligation combined with PTK 787; and 8) hepatic artery ligation combined with cisplatin and PTK 787. Survival time was recorded. Histology of the tumor and non-tumor tissues was studied at different time points after treatment. Apoptotic cells were detected by TUNEL staining. Expression of adhesion molecules and apoptosis-related molecules was determined by Western blot. In the in vitro study, an endothelial cell line was treated with hypoxia and hypoxia combined with PTK 787. The apoptotic cells were labeled with Annexin V and determined by flow cytometry. The levels of adhesion molecules, apoptosis-related molecules and cell cycle-related molecules were detected by Western blot. Results: Hepatic artery ligation combined with PTK 787 and the three-combination treatment significantly prolonged animal survival. The highest number of apoptotic cells was detected in the groups receiving hepatic artery ligation combined with PTK 787 and three-combination treatment. The expression of adhesion molecules was upregulated after hepatic artery ligation, whereas the augmentation was reversed by PTK 787. The in vitro study revealed that hypoxia induced an increased expression of adhesion molecules in the endothelial cells, whereas administration of PTK 787 significantly reversed the augmentation. PTK 787 further increased the number of apoptotic cells that was induced by hypoxia. Hypoxia combined with PTK 787 inhibited the expression of cell cycle-related molecules, and induced upregulation of pro-apoptotic molecules and downregulation of anti-apoptotic molecules. Conclusion: PTK 787 could enhance the therapeutic efficacy of hypoxia and chemotherapy in HCC through inhibiting the activation of endothelial cells and enhancing endothelial cell apoptosis, leading to angiogeneic blockade in tumor.