Clonal intratumor heterogeneity of promoter hypermethylation in breast cancer by MS-MLPA
Clonal intratumor heterogeneity of promoter hypermethylation in breast cancer by MS-MLPA
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DOI：
10.1038/modpathol.2013.207
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发表时间：
2014-06-01
期刊：
影响因子：
7.5
通讯作者：
van Diest, Paul J.
中科院分区：
文献类型：
--
作者：
Moelans, Cathy B.;de Groot, Jolien S.;van Diest, Paul J.
肿瘤内异质性可能导致采样偏倚，并可能对个性化医疗和生物标志物开发提出重大挑战。尽管许多研究调查遗传异质性，表观遗传肿瘤内异质性的启动子高甲基化很少被检查在乳腺癌。为了研究启动子超甲基化的克隆性肿瘤内异质性，我们对21例原发性乳腺癌中获得的多个空间分离样本进行了24个已建立的肿瘤抑制基因的甲基化特异性多重连接依赖探针扩增（MS-MLPA）。进行多区域分析，代表每名患者至少两个和最多五个肿瘤块，每个肿瘤块四个区域。在95%的乳腺癌中，不同肿瘤区域之间的一个或多个基因位点的甲基化结果是异质性的。频率递减的异质性位点依次为RASSF 1A（62%）、CDKN 2B（43%）、APC（38%）、GSTP 1（33%）、CDH 13（24%）、DAPK 1（19%）和CDKN 1B（5%）。在65%的肿瘤中，杂合性导致至少一个基因座的甲基化状态改变。对于大多数基因，患者间和区组间变异性对甲基化结果总变异的相对贡献相似。无论基因，内块变异的贡献是不重要的。总之，尽管个体乳腺癌之间存在甲基化状态的大多数变化，但在大多数原发性乳腺癌中观察到克隆表观遗传异质性，表明来自单个随机样本的甲基化结果可能不能代表整个肿瘤。
Intratumor heterogeneity may lead to sampling bias and may present major challenges to personalized medicine and biomarker development. Despite many studies investigating genetic heterogeneity, epigenetic intratumor heterogeneity of promoter hypermethylation has only rarely been examined in breast cancer. To examine clonal intratumor heterogeneity of promotor hypermethylation, we performed methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) for 24 established tumor-suppressor genes on multiple spatially separated samples obtained from 21 primary breast carcinomas. Multiregion analysis was performed, representing at least two and a maximum of five tumor blocks per patient and four areas per tumor block. Methylation results were heterogeneous at one or more genetic loci between different tumor regions in 95% of breast carcinomas. The most heterogeneous loci in decreasing frequency were RASSF1A (62%), CDKN2B (43%), APC (38%), GSTP1 (33%), CDH13 (24%), DAPK1 (19%), and CDKN1B (5%). Heterogeneity lead to a methylation status change in at least one locus in 65% of the tumors. For most genes, the relative contribution of between-patients and between-block variability to the total variation in methylation results was similar. Regardless of the gene, contribution of within-block variability was of little importance. In conclusion, although most variation in methylation status is present between individual breast cancers, clonal epigenetic heterogeneity is seen within most primary breast carcinomas, indicating that methylation results from a single random sample may not be representative of the whole tumor.