Abstract: Objective To investigate the expressions of p-Stat3，HIF-1α and VEGF in Hep-2 cells under hypoxia，and the effect of Stat3 antisense oligonucleotides (AS-ODN) on these expressions.Methods Expressions of p-Stat3，HIF-1α and VEGF of Hep-2 cells that were with or without Stat3 AS-ODN transfection，at hypoxic and normoxic conditions，were detected by flow cytometry.The survival rate of Hep-2 cells transfected with Stat3 AS-ODN and control groups were analyzed by MTT assay.Results The FI of p-Stat3 was up-regulated in 3h-hypoxia group，and it was stable after 6h at hypoxic condition.The FI of HIF-1α and VEGF increased after 6h and 12h at hypoxic condition. There was positive correlation between the expression of p-Stat3 and HIF-1α (r=0.691，P＜0.01).Compared to Stat3 S-ODN group and   lipofectamine  control group，the expressions of p-Stat3，HIF-1α and VEGF in Stat3 AS-ODN group at hypoxic condition were significantly decreased (P＜0.01 ). Pearson correlation analysis showed the significant positive correlation between the expressions of p-Stat3 and HIF-1α (r=0.912，P＜0.01).The survival rate of Hep-2 cell   reduced with the concentration augmentation of Stat3 AS-ODN (100nmol/L and 200nmol/L)，which were significantly different from the Stat3 S-ODN group and  HIF- 1α  and VEGFlipofectamine control group (P＜0.01).Conclusions Hypoxia can induce Stat3 activation in Hep-2 cells.The expression of p-Stat3 is earlier than that of  HIF-1α and VEGF.Blocking Stat3 can decrease the expression of HIF-1α under hypoxia，indicating Stat3 might modulate HIF-1α expression in Hep-2 cells at the hypoxic condition.

Key words: Stat3, Hypoxia, Antisense oligonucleotides, HIF-1α, Laryngeal carcinoma