Abstract: AIM: To explore the mechanisms of multidrug resistance in human gastric cancer by establishing a cisplatin(DDP) resistance BGC-823 cell line. METHODS: The human cancer BGC-823 cells were exposed in a gradually increasing dose of DDP.MTT assay was used to detect the cytotoxic activity of DDP against BGC-823 and BGC-823/DDP cells. The mRNA expression of Oct-4 was detected by RT-PCR analysis.The small interfering RNA was used to specifically knockdown Oct-4 in BGC-823/DDP cells. The protein expression of Oct-4 was determined by Western blot analysis. RESULTS: DDP resistance cell line BGC-823/DDP was established by DDP 30-34 weeks contionuous inducing.The IC₅₀ values of DDP against BGC-823 and BGC-823/DDP cells were (2.33±0.12)and (21.46±0.97) μmol/L by MTT assay, respectively.Compared with the BGC-823 cells, the resistance to cisplatin of BGC-823/DDP cells was 9.21 times. Semi-quantitative RT-PCR analysis showed that the mRNA expression of Oct-4 was upregulated in BGC-823/DDP cells.Western blot showed that the expression of Oct-4 protein was down-regulated by the chemical synthesis siRNA;After interfered the Oct-4 gene expression of BGC-823/DDP cells by siRNA,the IC₅₀ values of cisplatin against BGC-823/DDP cells was decreased from (22.04±1.84) to (6.15±0.53) μmol/L;there was no significant difference (P<0.01). CONCLUSION: The results show that Oct-4 gene expression plays an important role in gastric cancer with cisplatin resistance.

Key words: Gastric cancer, BGC-823 cell, Multidrug resistance, Oct-4 gene