Objectiv To observe the relation of estradiol-stimulated protein (esp1) expression with chromosome ploidy in A549 and Hela cells. Methods Total RNA was extracted from A549 and Hela cells respectively for cDNA. pIRE-S2-EGFP-ESP1 plasmid was transfected into the 2 corresponding tumor cells. Real-time quantitative PCR was used to detect esp1 gene expression. The chromosome changes were analyzed by VIDEOTEST-KARYO 3.1 and chromosome ploidy was analyzed with flow cytometry. Results After the tumor cells were transfected with pIRE-S2-EGFP-ESP1 plasmid

the expression of esp1 gene was up-regulated (P0.01)

chromosome number decreased (P0.01)

and chromosome ploidy reduced (P0.01). Conclusion The overexpression of esp1 gene inhibits the abnormal proliferation of tumor cells and decreases chromosome ploidy.