OBJECTIVE: To evaluate the influence of bcl-2 antisense oligodeoxynucleotides (AODN) on reversing cisplatin (DDP) resistance in ovarian carcinoma cell lines. METHODS: In the experiment groups, cisplatin resistant ovarian carcinoma cell line A2780/DDP cells were treated with cisplatin after oligodeoxynucleotides were transfected by lipofectamine. Cell proliferation was determined by counting the number of the cells continuously for six days. The expression level of bcl-2 mRNA was detected with reverse transcription polymerase chain reaction (RT-PCR) and protein was tested by immunofluorescence technique. The apoptosis of ovarian cancer cell lines was measured by DNA ladder assay. The inhibitory rate of cells was detected by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT). The cells treated with culture media were used as the negative control, and the untreated cells were used as the blank. RESULTS: The proliferation of AODN transfected cells was inhibited significantly compared with that in the control groups, and the logarithmic growth delayed for 24h. The expression of bcl-2 mRNA and bcl-2 protein in AODN transfected cells was 0.76 +/- 0.01 and 171.3 +/- 3.1 respectively. Compared with the expression of bcl-2 mRNA 1.56 +/- 0.03 and bcl-2 protein 105.3 +/- 1.7 in the blank, the difference was significant (P < 0.01), but compared with the same concentration of sense oligodeoxynucleotides (SODN) or random-oligodeoxynucleotides (RODN) transfected cells, the difference was not significant (P > 0.05). The AODN transfected cells were sensitive to DDP again, and the inhibitory rate was (97.49 +/- 1.00)%, which was higher than that of the negative control (P < 0.01). In the cells treated with 16 microg/ml AODN for 72 h followed by DDP, DNA ladder was obviously observed with agarose gel electrophoresis, but in the RODN and SODN transfected cells, DNA ladder could not be seen. CONCLUSION: Through inhibiting the expression of bcl-2 mRNA and protein and increasing the apoptosis, AODN can reverse the resistance to cisplatin in ovarian cancer cell line A2780/DDP.