中文摘要：

目的：探讨DNA甲基化抑制剂5-aza-2＇-deoxycitydine（5-aza—dC）影响胃癌细胞MGC803对奥沙利铂（0xaliPlatin，OXA）的化疗敏感性，及其与Ⅱ相代谢解毒酶GSTP1表达的相关性。方法：5-aza-dC处理MGC803，RT—PCR和Western—Blot方法检测GSTP1基因mRNA和蛋白表达。MSP法分析GSTP1基因启动子区甲基化状态。MTT法检测药物敏感性。结果：5-aza—dC诱导GSTP1基因启动子去甲基化，上调GSTPlmRNA和蛋白表达，降低了MGC803细胞对OXA的敏感性，24hIC，。值分别为对照组（13．15±1．7）μg/L、1μM 5-aza-dC处理组（24．54±2．1）μg/L、5μM 5-aza-dC处理组（30．81±1．3）μg／L及10μM 5-aza—dC处理组（51．72±1．6）μg／L，P值〈0．01，差异有统计学意义。结论：5-aza-dC降低胃癌细胞对奥沙利铂的敏感性，其机制与增强GSTP1表达有关。

英文摘要：

Objective： To explore the effect of 5-aza-2＇-deoxycytidine （5-aza-dC）, an inhibitor of DNA methyltransferase, on the sensitivity of human gastric cancer cell line MGC803 cells to oxaliplatin and its relationship with GSTP1. Methods： MGC803 cells were treated with 5-aza-dC. The expression of GSTP1 mRNA was detected using reverse transcription PCR （RT-PCR）. Protein expression was analyzed by Western blot. DNA methylation status of the GSTP1 gene promoter was assayed by methylation-specific PCR （MSP）. Drug sensitivity was detected by MTT method. Results： 5-aza-dC induced demethylation of the GSTP1 gene promoter. GSTP1 mRNA and protein expression were markedly upregulated by 5-aza-dC treatment by the 5th day. The 24 hour IC50s of the control group, the 11μM 5-aza-dC treatment group, the 5μM 5-aza-dC treatment group and the 101μM 5-aza-dC treatment group were （13.15±1.7）μg/L, （24.54±2.1）μg/L, （30.81±1.3）μg/L and （51.72±1.6）μg/L, with a significant difference among the treatment groups （P〈0.01）. Conclusion： 5-aza-dC decreases the sensitivity of gastric cancer cells to oxaliplatin through a mechanism related to an increase in GSTP1 expression.