Objective      To determine the expression of guanine nucleotide exchange factor Crk SH3-domain-binding guanine nucleotide-releasing factor (C3G) in epithelial ovarian cancer tissues and its role in the proliferation of human ovarian cancer cell line SKOV3.       Methods      C3G was detected by Western blotting in the tissue samples of epithelial ovarian cancer (

n

=40)

benign ovarian tumors (n=8) and normal ovarian (

n

=4)

respectively. Endogenous C3G was knocked-down by siRNA in SKOV3 cells. Then

MTT assay and plate colony formation ass

ay were used to evaluate the proliferation of cancer cells. Nude mice subcutaneous xenograft transplanted tumor model was established to assess tumor growth in vivo.       Results      The expression of C3G was significantly higher in epithelial ovarian cancer tissues than in benign ovarian tumors and normal ovarian tissues. The expression of C3G was 1.832±0.200 times higher in epithelial ovarian cancer tissues（

P

0.05） and 0.893±0.147 times higher in benign tumors when compared with normal ovarian tissues

respectively. Specific siRNA knocked down resulted in the expression of C3G decreased by 79.2% in SKOV3 cells

and significant decrease in cell proliferation and clone formation rate (

P

0.05). Nude mice xenograft transplanted tumor by C3G siRNA transfected SKOV3 cells had average smaller volume and lower weight of sub-cutaneous tumors (

P

0.05).       Conclusion      Nucleotide exchange factor C3G

over-expressed in most epithelial ovarian cancer tissues

facilitates the proliferation of ovarian cancer SKOV3 cells.