Klajic Jovana, Fleischer Thomas, Dejeux Emelyne, Edvardsen Hege, Warnberg Fredrik, Bukholm Ida, Lønning Per Eystein, Solvang Hiroko, Børresen-Dale Anne-Lise, Tost Jörg, Kristensen Vessela N
Department of Clinical Molecular Biology and Laboratory Science (EpiGen), Akershus University hospital, Division of Medicine, 1476 Lørenskog, Norway.
BMC Cancer. 2013 Oct 5;13:456. doi: 10.1186/1471-2407-13-456.
Aberrant DNA methylation of regulatory genes has frequently been found in human breast cancers and correlated to clinical outcome. In the present study we investigate stage specific changes in the DNA methylation patterns in order to identify valuable markers to understand how these changes affect breast cancer progression.
Quantitative DNA methylation analyses of 12 candidate genes ABCB1, BRCCA1, CDKN2A, ESR1, GSTP1, IGF2, MGMT, HMLH1, PPP2R2B, PTEN, RASSF1A and FOXC1 was performed by pyrosequencing a series of 238 breast cancer tissue samples from DCIS to invasive tumors stage I to IV.
Significant differences in methylation levels between the DCIS and invasive stage II tumors were observed for six genes RASSF1A, CDKN2A, MGMT, ABCB1, GSTP1 and FOXC1. RASSF1A, ABCB1 and GSTP1 showed significantly higher methylation levels in late stage compared to the early stage breast carcinoma. Z-score analysis revealed significantly lower methylation levels in DCIS and stage I tumors compared with stage II, III and IV tumors. Methylation levels of PTEN, PPP2R2B, FOXC1, ABCB1 and BRCA1 were lower in tumors harboring TP53 mutations then in tumors with wild type TP53. Z-score analysis showed that TP53 mutated tumors had significantly lower overall methylation levels compared to tumors with wild type TP53. Methylation levels of RASSF1A, PPP2R2B, GSTP1 and FOXC1 were higher in ER positive vs. ER negative tumors and methylation levels of PTEN and CDKN2A were higher in HER2 positive vs. HER2 negative tumors. Z-score analysis also showed that HER2 positive tumors had significantly higher z-scores of methylation compared to the HER2 negative tumors. Univariate survival analysis identifies methylation status of PPP2R2B as significant predictor of overall survival and breast cancer specific survival.
In the present study we report that the level of aberrant DNA methylation is higher in late stage compared with early stage of invasive breast cancers and DCIS for genes mentioned above.
调控基因的异常DNA甲基化在人类乳腺癌中经常被发现，并且与临床结果相关。在本研究中，我们调查DNA甲基化模式的阶段特异性变化，以识别有价值的标志物，从而了解这些变化如何影响乳腺癌的进展。
通过焦磷酸测序对一系列238个从导管原位癌（DCIS）到I至IV期浸润性肿瘤的乳腺癌组织样本进行12个候选基因ABCB1、BRCCA1、CDKN2A、ESR1、GSTP1、IGF2、MGMT、HMLH1、PPP2R2B、PTEN、RASSF1A和FOXC1的定量DNA甲基化分析。
对于6个基因RASSF1A、CDKN2A、MGMT、ABCB1、GSTP1和FOXC1，观察到DCIS和浸润性II期肿瘤之间甲基化水平存在显著差异。与早期乳腺癌相比，RASSF1A、ABCB1和GSTP1在晚期显示出显著更高的甲基化水平。Z评分分析显示，与II、III和IV期肿瘤相比，DCIS和I期肿瘤的甲基化水平显著更低。与野生型TP53的肿瘤相比，携带TP53突变的肿瘤中PTEN、PPP2R2B、FOXC1、ABCB1和BRCA1的甲基化水平更低。Z评分分析表明，与野生型TP53的肿瘤相比，TP53突变的肿瘤总体甲基化水平显著更低。ER阳性肿瘤与ER阴性肿瘤相比，RASSF1A、PPP2R2B、GSTP1和FOXC1的甲基化水平更高，HER2阳性肿瘤与HER2阴性肿瘤相比，PTEN和CDKN2A的甲基化水平更高。Z评分分析还表明，与HER2阴性肿瘤相比，HER2阳性肿瘤的甲基化Z评分显著更高。单因素生存分析确定PPP2R2B的甲基化状态是总生存和乳腺癌特异性生存的显著预测因子。
在本研究中，我们报告上述基因在浸润性乳腺癌晚期与早期以及DCIS相比，异常DNA甲基化水平更高。
