To investigate the effect of estrogen to STGC3 gene on CNE2 cell line in vitro and in vivo. The recombinant pcDNA3.1(+)/STGC3 plasmid was constructed and transfected into CNE2 cell line with lipofectamine 2000. CNE2 cell clones with stable STGC3 expression were obtained through G418 selection and identified by RT-PCR and Western blotting methods. The effect of β-estradiol on growth rate of pcDNA3.1(+)/ STGC3/CNE2 cell line was examined by cytometry. The pcDNA3.1(+)/STGC3/CNE2 cell line was inoculated subcutaneously in nude mice. Tumorigenicity diversity was analyzed in female and male nude mice. STGC3 expression was detected in tumor xenografts in nude mice by RT-PCR, immunohistochemistry and Western blotting methods. Cell morphologic changes were observed by microscope. Flow cytometry was used to analyze cell cycles. The results indicated that pcDNA3.1(+)/STGC3/CNE2 cell growth rate decreased after treated with β-estradiol in vitro. There were significant differences in tumor size and mass between pcDNA3.1(+)/ STGC3/CNE2 and control cases (P < 0.05). Furthermore, tumor size and mass had significant differences between male and female nude mice in the STGC3 transfection cases and tumor growth rate of pcDNA3.1(+)/ STGC3/CNE2 in the female nude mice was the lowest in all cases (P < 0.05). No significant difference was found between male and female nude mice in other control cases (P > 0.05). There were more cells blocked in G0/G1 phase in tumor xenografts of pcDNA3.1(+)/STGC3/CNE2 cell line of the female nude mice case than that in other cases. Data above indicated that estrogen might enhance the effect of STGC3 to inhibit CNE2 cell proliferation in vitro and in vivo.