Background & Aims: Solid tumors often become hypoxic,leading to activation of hypoxia-response genes.We investigated the effects of overexpression of the hypoxia response genes eIF5A2 (eukaryotic initiation factor 5A2) in esophageal squamous cell carcinoma (ESCC).Methods: We used quantitative real-time PCR and immunohistochemistry analyses to compare expression of eIF5A2 between paired ESCC samples and non-tumor esophageal tissues,and fluorescence in situ hybridization to detect gene copy number alterations.Luciferase reporter and chromatin immunoprecipitation assays were used to study interactions between eIF5A2 and HIF1a (hypoxia-inducible factor-1αt).We determined the effects of eIF5A2 overexpression and knockdown in ESCC cell lines,and growth of ESCC xenograft tumors in nude mice.Results: Levels of eIF5A2 mRNA and protein were increased in over 40% of ESCC samples,compared with matched non-tumor tissues,along with levels of HIFlα and VEGF.Increased levels of EIF5A2 were significantly associated with ESCC metastasis to lymph nodes (P<.001) and tissue invasion (P=.037),and shorter survival times of patients (P<.001).Amplification ofeIF5A2 was detected in 35.14% of ESCC samples that overexpressed eIF5A2.Hypoxia increased expression of eIF5A2 4-to 8-fold in ESCC cell lines;we observed bidirectional regulation between eIF5A2 and HIF1α.Transient transfection of ESCC cell lines with eIF5A2 increased their migratory and invasive abilities and markers of the epithelial to mesenchymal transition,whereas eIF5A2 knockdown or HIF1 inhibition reduced these.In mice,xenograft tumors grown from ESCC cells that expressed eIF5A2 formed tumors more rapidly than cells that expressed only vector (controls);they also expressed higher levels of HIFlα and VEGF,and formed more microvessels than controls.Knockdown of eIF5A2 in ESCC cells with interfering RNAs reduced their growth as xenograft tumors in mice,particularly when mice were given docetaxel or cisplatin.Conclusions: eIF5A2 is overexpressed by gene amplification or hypoxia in ESCCs,and associated with upregulation of HIF1,metastasis,and shorter survival times of patients.Increased expression of eIF5A2 increases matastasis and angiogenesis in ESCC via the HIF1a-mediated signaling pathway.