Blockade of therapy-induced acute recruitment of bone marrow-derived CXCR4+Flt-1+ hemangiocytes inhibits hypoxia-induced tumor angiogenesis in hepatocellular carcinoma

Abstract

Objective: Some therapies, such as transcatheter arterial chemoembolization (TACE) for the treatment of unresectable hepatocellular carcinoma (HCC), can induce a hypoxic condition to tumor cells, leading to an increased production of angiogenic factors, mobilization of angiogenic cells and subsequent tumor angiogenesis and growth. We design a study to investigate whether blockade of acute recruitment of bone marrow-derived CXCR4+Flt-1+ cells (hemangiocytes) using a CXCR4 antagonist, CTCE-9908 (Chemokine Therapeutics Corp.), could inhibit post-treatment tumor angiogenesis and growth. Methods: An orthotopic HCC model was generated by injection of rat HCC cells into the left lobe of the liver of Buffalo rats. Two weeks after tumor cell inoculation, hepatic artery ligation (HAL), which mimics the procedure of TACE, was performed to induce ischemic hypoxia to tumor cells. CTCE-9908 was administered with HAL at the doses of 12.5 or 25 mg/kg/day. Survival time was recorded. Animals were sacrificed at different time points for tissue and blood sample collection. Flow cytometry was performed to evaluate the number of hemangiocytes in the bone marrow and circulation, and the number of apoptotic cells in the bone marrow. Immunohistochemical staining was conducted to assess the expression of CXCR4 and von Willebrand factor (vWF), a marker for microvessel density (MVD) in the tumor tissues. Results: HAL combined with CTCE-9908 significantly reduced tumor size and prolonged animal survival, compared to HAL alone. HAL induced increased areas of tumor necrosis, while CTCE-9908 combined with HAL generated more necrotic areas in the tumor. HAL increased the number of CXCR4+Flt-1+ cells in the bone marrow and circulation, and augmented the number of CXCR4+ cells in the tumor tissues, which could be blocked by the administration of CTCE-9908 with HAL. CTCE-9908 combined with HAL increased the number of apoptotic CXCR4+ cells in the bone marrow, and decreased the MVD in the tumor tissues, compared to HAL alone. Conclusion: Targeting CXCR4+Flt-1+ hemangiocyte mobilization using CTCE-9908 could inhibit hypoxia-induced tumor angiogenesis and growth, and thus enhance the therapeutic efficacy of TACE for the treatment of HCC. CTCE-9908 has been assessed in a Phase I/II clinical trial, with preliminary data presented at the 2007 AACR Molecular Targets Conference. Based on the present animal study, a Phase II trial of combined TACE and CTCE-9908 treatment for unresectable HCC is being planned to be conducted in 2008.