Stepwise DNA methylation changes are linked to escape from defined proliferation barriers and mammary epithelial cell immortalization.
Stepwise DNA methylation changes are linked to escape from defined proliferation barriers and mammary epithelial cell immortalization.
复制标题
DOI：
10.1158/0008-5472.can-08-4977
复制
发表时间：
2009-06-15
期刊：
影响因子：
11.2
通讯作者：
Futscher BW
中科院分区：
文献类型：
--
作者：
Novak P;Jensen TJ;Garbe JC;Stampfer MR;Futscher BW
在癌症发生过程中DNA甲基化变化的时间和进展还不完全清楚。为了建立恶性转化过程中异常DNA甲基化事件的时间轴，我们分析了同基因人乳腺上皮细胞（HMEC）转化培养模型中全基因组DNA甲基化模式。为了获得永生和恶性，培养的有限寿命HMEC必须克服两个不同的增殖障碍。第一个屏障，停滞，是由视网膜母细胞瘤蛋白介导的，可以通过p16 INK4A表达的丧失来克服。逃脱停滞并继续增殖的HMEC在遇到第二个更严格的增殖障碍之前变得基因组不稳定，这是由于端粒磨损导致的端粒功能障碍。获得端粒酶表达的罕见细胞可能会逃避这一障碍，变得永生，并进一步发展恶性性质。我们对HMEC从有限寿命过渡到恶性转化的分析表明，异常DNA甲基化变化在转化过程的早期以逐步的方式发生。第一个异常的DNA甲基化步骤与克服停滞相一致，并导致几个到数百个变化，这取决于停滞是如何被克服的。第二步与永生化相一致，并导致数百个额外的DNA甲基化变化，无论永生化途径如何。这些DNA甲基化变化中的大多数也在恶性乳腺癌细胞中发现。这些结果表明，大规模的表观遗传重塑发生在乳腺癌发生的最早阶段，在时间上将DNA甲基化变化与克服细胞增殖障碍联系起来，并提供了一个潜在的表观遗传生物标志物库，可能在乳腺癌风险评估中有用。
The timing and progression of DNA methylation changes during carcinogenesis are not completely understood. To develop a timeline of aberrant DNA methylation events during malignant transformation, we analyzed genome-wide DNA methylation patterns in an isogenic human mammary epithelial cell (HMEC) culture model of transformation. To acquire immortality and malignancy, the cultured finite lifespan HMEC must overcome two distinct proliferation barriers. The first barrier, stasis, is mediated by the retinoblastoma protein and can be overcome by loss of p16 INK4A expression. HMEC that escape stasis and continue to proliferate become genomically unstable before encountering a second more stringent proliferation barrier, telomere dysfunction due to telomere attrition. Rare cells that acquire telomerase expression may escape this barrier, become immortal, and develop further malignant properties. Our analysis of HMEC transitioning from finite lifespan to malignantly transformed showed that aberrant DNA methylation changes occur in a stepwise fashion early in the transformation process. The first aberrant DNA methylation step coincides with overcoming stasis, and results in few to hundreds of changes, depending upon how stasis was overcome. A second step coincides with immortalization, and results in hundreds of additional DNA methylation changes, regardless of the immortalization pathway. A majority of these DNA methylation changes are also found in malignant breast cancer cells. These results show that large-scale epigenetic remodeling occurs in the earliest steps of mammary carcinogenesis, temporally links DNA methylation changes and overcoming cellular proliferation barriers, and provides a bank of potential epigenetic biomarkers that may prove useful in breast cancer risk assessment.