Hartsough M T, Clare S E, Mair M, Elkahloun A G, Sgroi D, Osborne C K, Clark G, Steeg P S
Division of Clinical Sciences, National Cancer Institute, NIH, Bethesda, Maryland 20892, USA.
Cancer Res. 2001 Mar 1;61(5):2320-7.
We hypothesize that elevation of Nm23-H1 expression in micrometastatic breast cancer cells may inhibit their metastatic colonization and further invasion, and induce differentiation, thus resulting in a clinical benefit. The current study investigated the possible contribution of DNA methylation to the regulation of Nm23-H1 expression, based on the observation that two CpG islands are present in its promoter. 5-Aza-2'-deoxycytidine (5-Aza-CdR), a DNA methylation inhibitor, increased the Nm23-H1 expression of 5 of 11 human breast carcinoma cell lines in vitro, including 3 of 3 metastatically competent lines. Increased Nm23-H1 expression was accompanied by a reduction in motility in vitro, with minimal effect on proliferation. Both increased Nm23-H1 expression and decreased motility were observed using low (75 nM) concentrations of 5-Aza-CdR. Array analysis of MDA-MB-231 breast carcinoma cells treated with 5-Aza-CdR confirmed the elevation of nm23-H1 mRNA, whereas relatively few other genes exhibited altered expression. Bisulfite sequencing of the two CpG islands in a panel of cell lines and in 20 infiltrating ductal carcinomas revealed that one island (-3090 bp to -3922 bp) exhibited infrequent differential methylation. The data indicate that DNA methylation inhibitors can directly or indirectly cause both elevation of Nm23-H1 expression and decreased function in one aspect of metastasis, motility.
我们推测，微转移乳腺癌细胞中Nm23-H1表达的升高可能会抑制其转移定植和进一步侵袭，并诱导分化，从而带来临床益处。基于在其启动子中存在两个CpG岛这一观察结果，本研究调查了DNA甲基化对Nm23-H1表达调控的可能作用。DNA甲基化抑制剂5-氮杂-2'-脱氧胞苷（5-Aza-CdR）在体外增加了11种人乳腺癌细胞系中5种细胞系的Nm23-H1表达，其中包括3种具有转移能力的细胞系中的3种。Nm23-H1表达的增加伴随着体外运动能力的降低，对增殖的影响最小。使用低浓度（75 nM）的5-Aza-CdR时，观察到了Nm23-H1表达增加和运动能力降低。对用5-Aza-CdR处理的MDA-MB-231乳腺癌细胞进行的阵列分析证实了nm23-H1 mRNA的升高，而相对较少的其他基因表现出表达改变。对一组细胞系和20例浸润性导管癌中的两个CpG岛进行亚硫酸氢盐测序发现，一个岛（-3090 bp至-3922 bp）表现出不常见的差异甲基化。数据表明，DNA甲基化抑制剂可直接或间接导致Nm23-H1表达升高，并在转移的一个方面即运动能力方面导致功能降低。
