脾酪氨酸激酶基因的再激活对胃癌生成和发展的影响

目的探讨去甲基化酶5-氮-2＇-脱氧胞苷对脾酪氨酸激酶（Syk）基因再表达的影响，以及Syk基因的再表达对胃癌肿瘤生成和发展的影响。方法分别用RT-PCR和MSP法检测SGC7901、MGC803、MKN28和MKN45细胞株中Syk基因表达及甲基化情况；用5-氮-2＇-脱氧胞苷处理人胃癌细胞株5GC7901后，检测此细胞株中Syk基因的甲基化及再表达情况，并用此治疗过的细胞株和未经治疗的细胞株分别接种于裸鼠皮下，对比观察裸鼠的成瘤率。结果SGC7901和MKN45细胞株中没有检测到Syk基因的表达，但可检测到Syk基因的甲基化。检测用5-氮-2＇-脱氧胞苷处理过的人胃癌SGC7901细胞株，Syk基因启动子没有甲基化，RT-PCR可检测到有Syk基因。用无Syk基因表达的SGC7901细胞株接种于10只对照组裸鼠皮下，8周后均有肿块生成；而用有Syk基因再表达的细胞株接种于另10只裸鼠（治疗组）皮下，8周后只有3只有肿块生成；对照组裸鼠的成瘤率显著高于治疗组（χ^2=7．91，P〈0．05）。结论5-氮-2＇-脱氧胞苷通过去甲基化使SGC7901细胞株中Syk基因再表达，Syk基因的再表达抑制了胃癌的生成和发展。

Effect of spleen tyrosine kinase expression re-activation by inhibition of DNA methylation on oncogenesis growth of gastric cancer

OBJECTIVE: To explore the effects of 5-Aza-2'-deoxycytidine on spleen tyrosine kinase (Syk) expression by inhibition of DNA methylation and the effect of re-activation of Syk on oncogenesis of gastric cancer. METHODS: Syk mRNA of SGC7901, MGC803, MKN28 and MKN45 cell lines were analyzed by RT-PCR, and Syk methylation were detected by MSP. 5-aza-CDR was used to incubate with human gastric cancer cell line SGC7901, Methylation of Syk promoter region was detected by MSP and RT-PCR technique was used to detected Syk gene in the methylated and silenced Syk gene in the cell line SGC7901. Meanwhile, cell lines were inoculated into subcutaneous tissue of nude mice. RESULTS: No Syk mRNA were found in SGC7901 and MKN45 gastric cancer cell lines, but methylation of Syk were detected in those cell lines. No methylation of Syk promoter region was found and Syk gene was detected in the Syk-negative cell line SGC7901 after incubated with 5-aza-CDR. Of 10 nude mice which were inoculated SGC7901(Syk(+)), 3 were observed macroscopic tumor 8 weeks after the injection. On contrast, tumors were found in 10 nude mice which were inoculated SGC7901 (Syk(-)) 8 weeks after the injection, a significant difference was noted between the two groups (chi (2)=7.91, P<0.05). CONCLUSION: Syk gene is re-expressed in the cell line SGC7901 by demethylation with 5-aza-CDR. Syk gene re-expression suppress the malignant oncogenesis and growth of human gastric cancer.