DNMT在胃癌中的表达及DNMT抑制剂5-氮杂-2'-脱氧胞苷对胃癌的影响

摘要

目的:研究DNA甲基化转移酶(DNMT)各亚型DNMT1、DNMT2、DNMT3A、DNMT3B和DNMT3L在胃癌与胃黏膜中的表达特点,并分析DNMT抑制剂5-氮杂-2-脱氧胞苷对胃癌和胃黏膜细胞的影响.方法:免疫组化法对60例胃癌与癌旁组织行5种DNMT表达研究.免疫荧光法和Western免疫印迹法对SGC-7901、MKN-45(胃癌细胞)和GES-1(胃黏膜细胞)行5种DNMT表达研究.噻唑蓝比色法和流式细胞术分析5-氮杂-2-脱氧胞苷对SGC-7901、MKN-45和GES-1增殖、细胞周期和凋亡的影响.结果:胃癌与癌旁组织均有5种DNMT不同程度表达,但胃癌组织DNMT1和DNMT3A表达显著低于癌旁组织(P＜0.01),DNMT2和DNMT3L表达也低于癌旁组织(P＜0.05),只有DNMT3B在胃癌与癌旁组织中无显著差异(P＞0.05).胃癌细胞(SGC-7901和MKN-45)与胃黏膜细胞(GES-1)亦有部分DNMT表达,除DNMT3B在胃黏膜细胞表达较强外,余DNMT在胃癌与胃黏膜细胞中无显著差异.5-氮杂-2-脱氧胞苷对胃癌与胃黏膜细胞的增殖率、周期分布和凋亡率并无显著影响.结论:DNMT在胃癌中表达呈降低趋势,抑制DNMT对胃癌细胞的增殖和凋亡无显著影响.%ADM: To investigate the protein expression of DNA methyltransferases ( DNMT1, DNMT2, DN-MT3 A, DNMT3 B and DNMT3 L ) in gastric cancer and the effects of DNMT inhibitor ( 5 — aza — 2' — deoxycytidine ) on gastric cancer. METHODS: The method of immunohistochemistry was used to detect DNMT expression in 60 pairs of gastric cancer and corresponding non - cancerous tissues. The expression of DNMT in gastric cancer cells ( SGC -7901 and MKN — 45 ) and gastric mucosa cells ( GES — 1 ) was detected by immunofluorescence and Western blotting. The proliferation, cell cycle and apoptosis in the cell lines of SGC —7901, MKN —45 and GES — 1 were determined by MTT assay and flow cytometry with 5 - aza - 2' - deoxycytidine treatment. RESULTS: Both gastric cancer and corresponding non - cancerous tissues expressed 5 kinds of DNMT proteins, but the expression levels of DNMT1 and DNMT3A were significantly lower in gastric cancer than those in non — cancerous tissues ( P <0.01 ). The expression levels of DNMT2 and DNMT3L were also lower in the cancer than those in non - cancerous tissues ( P <0. 05 ). No difference of DNMT3B expression level between cancer and non - cancerous tissues was observed ( P > 0.05 ). On the other hand, the cells lines of SGC - 7901, MKN -45 and GES — 1 also expressed DNMT proteins. Except DNMT3B, no difference of the other kinds of DNMT between gastric cancer cells and gastric mucosa cells was observed. DNMT inhibitor 5 — aza — 2' — deoxycytidine did not have any effect on the growth rate, cell cycle distribution or apoptotic rate in gastric cancer cells and gastric mucosa cells. CONCLUSION : Gastric cancer expresses low levels of DNMT proteins than normal gastric mucosa. 5 — Aza — 2' — deoxycytidine is not useful for treating gastric cancer.