Antiangiogenic Effects Of Extracellular Tie-2 Receptor (ExTie-2) In A Nude Murine Model Of Gastric Cancer

Purpose: Angiogenesis is essential for tissue repair and regeneration during wound healing but also plays important roles in many pathological processes including tumour growth and metastasis. We explored the eukaryotic expression of Extracellular domains of murine Tie-2 in gastric cancer cell line SGC-7901,then construct a cancer model in nude mice to study the therapeutic potential of blocking the angiopoietins 1,2 /Tie-2 receptor pathway.Materials and Methods:Part 1. Murine ExTie-2 is a truncated extracelluar region of Tie-2 (containing three EGF repeats sandwiched between two IgG repeats).we fused it with pcDNA 3.1+ plasmid (Supplied by Doctor WEN Yan-jun,The Key Laboratory of Biotherapy of Human Diseases of Ministry of Education, P.R.China and Cancer Center, West China Hospital, Sichuan University, Chengdu, China). The plasmid was transfected into SGC-7901 cells by Lipofectamine reagent. Expression of ExTie-2 protein was detected by western blot analysis and immunohistochemistry staining.Part 2. BALB/c-nu/nu mice were inoculated with SGC-7901 gastric cancer cells on the dorsal aspect of the right foot-pad. Animals with established tumors (2 weeks after inoculation, 5 mm in diameter) were randomized into four groups: A (combination therapy); B (hypodermic inject pcDNA 3.1+ ExTie-2 plasmid alone);C(intraperitoneal inject 5-fluorouracil alone);and D(normal saline,NS)groups. Mice in group E were inoculated with SGC-7901 gastric cancer cells which were transfected with pcDNA 3.1+ ExTie-2 (mice) plasmid on the dorsal aspect of the right foot-pad the same time. Tumor size was measured weekly.36 days after implantation; mice were sacrificed and autopsied, mean tumor volumes were calculated. In addition,microvessel density (MVD) of tumor were detected by immunohistochemistry staining. Statistical differences between pairs of groups were determined using pair t test.Results: Extracellular Tie-2 receptor proteins were found by immunohistochemistry staining and Western blot analysis in SGC-7901 cells transfected with pcDNA 3.1+ExTie-2 (mice) plasmid. Tumor volumes of mice in group A+B and group E were significantly smaller than those in group C+D (P＜0.05). significant inhibitory effect on MVD level was observed in A+B and E group (P＜0.05).Conclusion: Our findings suggest that ExTek protein has inhibitory effect on tumor growth in nude mice model of human gastric cancer. This study may represent a novel potential utility of gene therapy for systemic delivery of an antiangiogenic agent targeting an endothelium specific receptor, Tie-2.