ABSTRACT
Hepatocellular cancer (HCC) is the fifth most common malignancy worldwide with 660,000 deaths annually. Studies of the molecular pathophysiology of HCC have shown that growth factors and their corresponding receptors are commonly overexpressed and/or dysregulated in HCC. Activation of these receptors and their downstream signaling pathways can lead to angiogenesis, cell proliferation, survival and metastasis of HCC. Hence, agents that specifically block their activation and signaling cascades would be valuable for treatment of HCC. Many small molecular tyrosine kinase inhibitors (TKIs) and antibodies have been tested in various phases of clinical trials. Although sorafenib has been shown to improve overall survival of patients with advanced HCC, the improvement is marginal and many patients eventually turn out to be refractory to this therapy. Thus, there is a pressing need to identify new drugs and effective treatments for this fatal disease. This review summarizes the pre-clinical and clinical data on the efficacy of the emerging tyrosine kinase inhibitors as well as the rationale for combination therapies for advanced HCC treatment. Understanding the mechanisms of action of these therapeutic agents and methods of combining these drugs may help to increase their efficacy, reduce toxicity, and improve overall survival and quality of life in patients with HCC.
Subject(s)
Carcinoma, Hepatocellular/drug therapy , Liver Neoplasms/drug therapy , Protein-Tyrosine Kinases/antagonists & inhibitors , Protein-Tyrosine Kinases/metabolism , Signal Transduction/drug effects , Benzenesulfonates/pharmacology , Benzenesulfonates/therapeutic use , Carcinoma, Hepatocellular/metabolism , Humans , Liver Neoplasms/metabolism , Niacinamide/analogs & derivatives , Phenylurea Compounds , Protein Kinase Inhibitors/pharmacology , Protein Kinase Inhibitors/therapeutic use , Protein-Tyrosine Kinases/immunology , Pyridines/pharmacology , Pyridines/therapeutic use , SorafenibABSTRACT
Gastric cancer is a deadly disease for which current therapeutic options are extremely limited. Vascular endothelial growth factor receptors and platelet-derived growth factor receptors regulate gastric cancer cell proliferation, invasion, and tumor angiogenesis. In the present study, we report that sorafenib therapy effectively inhibited tumor growth and angiogenesis in tumor xenografts. These were associated with reduction in the phosphorylation of vascular endothelial growth factor receptor-2 Tyr951, c-Kit Tyr568/570, platelet-derived growth factor receptor-beta Tyr1021, and Akt Ser473 and Thr308, down-regulation of positive cell cycle regulators, increased apoptosis, and up-regulation of p27. Sorafenib treatment also caused up-regulation of p-c-Raf Ser338 and p-extracellular signal-regulated kinase (ERK) Thr202/Tyr204 in gastric cancer xenografts. The combination of sorafenib and MAP/ERK kinase inhibitor AZD6244 enhances the effectiveness of each compound alone. Potential effect of sorafenib/AZD6244 included increase in proapoptotic Bim. Our data show that MAP/ERK kinase inhibition enhances the antitumor activity of sorafenib in vivo, supporting a rationale for multitargeted suppression of the angiogenesis and ERK signaling network in gastric cancer therapy.
