Ateeq Bushra, Unterberger Alexander, Szyf Moshe, Rabbani Shafaat A
Department of Medicine, McGill University, Montreal, Quebec, Canada.
Neoplasia. 2008 Mar;10(3):266-78. doi: 10.1593/neo.07947.
The mechanism of action of DNA methylation inhibitor 5-aza-2'-deoxycytidine (5-aza-CdR), a potential anticancer agent is believed to be activated by the demethylation of tumor suppressor genes. We tested here the hypothesis that demethylating agents also demethylate and activate genes involved in invasion and metastasis and therefore might increase the risk of developing tumor metastasis. The effect of 5-aza-CdR on noninvasive human breast cancer cells MCF-7 and ZR-75-1 was evaluated by cell proliferation, invasion, and migration assay. The ability of 5-aza-CdR to activate a panel of silenced prometastatic and tumor suppressor genes was evaluated using reverse transcription-polymerase chain reaction and bisulfite DNA sequence analysis in vitro and for change in tumor growth and gene expression in vivo. Treatment of MCF-7 and ZR-75-1 with 5-aza-CdR diminished cell proliferation, induced tumor suppressor RASSF1A, and altered cell cycle kinetics' G(2)/M-phase cell cycle arrest. While these effects of 5-aza-CdR slowed the growth of tumors in nude mice, it also induced a battery of prometastatic genes, namely, uPA, CXCR4, HEPARANASE, SYNUCLEIN gamma, and transforming growth factor-beta (TGF-beta), by demethylation of their promoters. These results draw attention to the critical role of demethylation as a potential mechanism that can promote the development and progression of tumor metastasis after demethylation therapy as an anticancer treatment.
DNA甲基化抑制剂5-氮杂-2'-脱氧胞苷（5-aza-CdR）作为一种潜在的抗癌药物，其作用机制被认为是通过肿瘤抑制基因的去甲基化而激活。我们在此检验了这样一个假说，即去甲基化剂也会使参与侵袭和转移的基因发生去甲基化并激活这些基因，因此可能会增加肿瘤转移发生的风险。通过细胞增殖、侵袭和迁移实验评估了5-aza-CdR对非侵袭性人乳腺癌细胞MCF-7和ZR-75-1的影响。利用逆转录-聚合酶链反应和亚硫酸氢盐DNA序列分析在体外评估了5-aza-CdR激活一组沉默的促转移基因和肿瘤抑制基因的能力，并在体内评估了其对肿瘤生长和基因表达的影响。用5-aza-CdR处理MCF-7和ZR-75-1细胞可减少细胞增殖，诱导肿瘤抑制基因RASSF1A，并改变细胞周期动力学，使细胞停滞于G(2)/M期。虽然5-aza-CdR的这些作用减缓了裸鼠体内肿瘤的生长，但它也通过去甲基化其启动子而诱导了一系列促转移基因，即尿激酶型纤溶酶原激活剂（uPA）、趋化因子受体4（CXCR4）、乙酰肝素酶、γ-突触核蛋白以及转化生长因子-β（TGF-β）。这些结果提醒人们注意去甲基化作为一种潜在机制在去甲基化治疗作为抗癌疗法后促进肿瘤转移发生和发展过程中的关键作用。
