Objective    To study the reversing effect of hMLH1 gene on cisplatin resistance in ovarian cancer cell line SKOV3/DDP and its underlying mechanism.     Methods      SKOV3/DDP cells were transfected with recombinant eukaryotic expression plasmid pcDNA3.1-hMLH1 and plasmid pcDNA3.1

respectively

by using lipofectamine 2000. Expression of hMLH1 mRNA and protein was detected by RT-PCR and Western blotting

respectively. Chemosensitivity of SKOV3/DDP cells to cisplatin was assayed by MTT assay. KOV3/DDP cell apoptosis was detected by flow cytometr

y (FCM) and Western blotting

respectively

after treatment with cisplatin.     Results    MTT assay showed the expression level of hMLH1 mRNA and protein was significantly higher （P0.05） and the IC

50

value（13.95±2.45）for cisplatin was obviously lower in SKOV3/DDP cells 24 h after transient transfection with hMLH1 gene than in controls（94.16±5.18）. FCM and Western blotting showed that the apoptotic rate of SKOV3/DDP cells transfected with the hMLH1 gene was higher (3.33%±2.31％) than that of controls and the expression level of Bcl-2 was lower in SKOV3/DDP cells transfected with the hMLH1 gene （1.35±0.39） than that in controls （P0.05）.     Conclusion     The hMLH1 gene can increase the chemosensitivity of human ovarian cancer cells to cisplatin

which may be related to the down-regulation of Bcl-2 expression and improvement of cell apoptosis.