Abstract: Objective To investigate the effect of NKX6.3 on proliferation，apoptosis，and invasion of esophageal cancer cells and its possible mechanism. Methods Human esophageal cancer EC9706 cells were transfected and divided into NKX6.3 group（transfected with NKX6.3），miR-NC group（transfected with blank plasmid） and blank control group（Control group）. CCK-8 method was used to detect cell proliferation，the flow cytometry was applied to detect intracellular reactive oxygen species，mitochondrial membrane potential and apoptosis of esophageal cancer cells，and Transwell method was applied to detect invasion of esophageal cancer cells. Expression of proliferation-related protein（Ki67），invasion-related proteins（Vimentin，E-cadherin，and N-cadherin） and apoptosis-related proteins（Bcl-2，Bax，and Caspase-3） were detected by Western blot. Results Statistically significant difference（P<0.01） existed among the Control group，miR-NC group and the expression of NKX6.3 in EC9706 cell in NKX6.3 group，cell proliferation capacity，intracellular reactive oxygen species，mitochondrial membrane potential，cell apoptosis and invasion of esophageal cancer cells，as well as in the expression of Ki67，Vimentin，E-cadherin，N-cadherin，Bcl-2，Bax and Caspase-3 proteins. The expression of NKX6.3，intracellular reactive oxygen species，apoptosis rate，and Vimentin，E-cadherin，Bax and Caspase-3 proteins expression in the NKX6.3 group were significantly higher than those in the miR-NC group，while mitochondrial membrane potential，cell proliferation rate，cell invasion number，and the expression of N-cadherin and Bcl-2 proteins were significantly lower（P<0.01）. Conclusion NKX6.3 can inhibit the proliferation and invasion of esophageal cancer cells and promote cell apoptosis，probably through regulating the expression of proliferation-related proteins and the level of reactive oxygen species in esophageal cancer cells.

Key words: Esophageal cancer, NKX6.3, Reactive oxygen species, Proliferation, Apoptosis, Invasion