Apurinic / Apyrimidinic endonuclease - 1 is associated with 1 angiogenesis and VEGF production via upregulation of COX - 2 2 expression in esophageal cancer tissues 3 Running title : APE - 1 is associated with angiogenesis and VEGF production

22 Objective Apurinic/apyrimidinic endonuclease-1 (APE-1) is a key enzyme 23 responsible for DNA base excision repair (BER) and is also a multifunctional protein 24 such as redox effector for several transcriptional factors. Our study was designed to 25 investigate APE-1 expression and to study its interaction with COX-2 expression and 26 VEGF production in the esophageal cancer. 27 Materials and Methods The expression of APE-1, COX-2, MCP-1, CCR2 and 28 VEGF were evaluated by immunohistochemistry in 65 human esophageal squamous 29 cell carcinoma (ESCC) tissues. Real-time PCR and western blotting were performed 30 to detect mRNA and protein expression of APE-1 and p-STAT3 expression in MCP-1 31 stimulated ESCC cell lines (KYSE 220 and EC-GI-10). SiRNA for APE-1 was treated 32 to determine the role of APE-1 in the regulation of COX-2 expression, VEGF 33 production and anti-apoptotic effect against cisplatin. 34 Results In human ESCC tissues, nuclear localization of APE-1 was observed in 35 92.3% (60/65) of all tissues. There was a significant relationship (p=0.029, R=0.49) 36 between nuclear APE-1 and cytoplasmic COX-2 expression levels in the esophageal 37 cancer tissues. In KYSE 220 and EC-GI-10 cells, MCP-1 stimulation significantly 38 increased mRNA and protein expression of APE-1. Treatment with siRNA for APE-1 39 significantly inhibited p-STAT3 expression levels in MCP-1-stimulated both cells. 40 Furthermore, treatment of siRNA for APE-1 significantly reduced COX-2 expression 41 and VEGF production in MCP-1-stimulated esophageal cancer cell-lines. Treatment 42 with APE-1 siRNA significantly increased apoptotic levels in cisplatin-incubated 43 KYSE 220 and EC-GI-10 cells. 44 Conclusion APE-1 is overexpressed and associated with COX-2 expression and 45