Objective:To observe the effect and underlying mechanism of down-regulation of VEGFA on the radiosensitivity of esophageal cancer ECA-109 cells.Methods:Esophageal cancer cells were divided into four groups: sh-VEGFA group, vector control group, X-ray plussh-VEGFA group and X-ray plus vector group. The expressions of VEGFA gene and protein were detected by qPCR and Western blot, respectively. Cell proliferation and survival was measured by CCK8 assay and cloning formation, respectively. Cell apoptosis was detected by flow cytometry, and γ-H2AX foci were detected by immune-fluorescence assay.Results:Compared with the vector group, the expression of VEGFA gene was decreased in sh-VEGFA group ( t=11.98, P<0.05), and the expression of VEGFA protein was also reduced( t=12.38, P<0.05). After VEGFA being down-regulated, the cell proliferation( A450)was obviously inhibited( t=2.78, 7.25, 21.93, 13.21, P<0.05), and the cell clone formation of the sh-VEGFA group was significantly decreased so that D0, Dqand SF2 of sh-VEGFA group were decreased( t=5.83, 8.56, 7.68, P<0.05), and SERD0and SERDqwere increased. Compared with the vector group, the apoptosis rate in the sh-VEGFA group and the X-ray group was significantly increased and further increased in the sh-VEGFA plus X-ray group( t=17.63, 22.48, 33.87, P<0.05), and the number of γ-H2AX foci in both sh-VEGFA and vector groups were significantly increased within 2 h after X-ray irradiation. At 24 h after irradiation, the number of γ-H2AX foci returned to normal level in the vector group but remained at a higher level in the sh-VEGFA group ( t=7.00, P<0.05). Conclusions:Down-regulation of VEGFA inhibits the proliferation and colony formation, promotes apoptosis and hence increases the radiosensitivity of esophageal carcinoma cells via a pathway related to DNA damage repair.