Aberrant methylation of the BRCA1 CpG island promoter is associated with decreased BRCA1 mRNA in sporadic breast cancer cells
Aberrant methylation of the BRCA1 CpG island promoter is associated with decreased BRCA1 mRNA in sporadic breast cancer cells
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DOI：
10.1038/sj.onc.1202086
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发表时间：
1998-10-08
期刊：
影响因子：
8
通讯作者：
Futscher, BW
中科院分区：
文献类型：
--
作者：
Rice, JC;Massey-Brown, KS;Futscher, BW
BRCA1 mRNA在散发性乳腺癌细胞中减少，尽管缺乏突变。由于在BRCA1基因的5'端发现了CpG岛，我们假设散发性乳腺癌中BRCA1 mRNA的减少与CpG岛的异常胞嘧啶甲基化有关。我们采用RT-PCR技术检测了正常人乳腺上皮细胞（HMECs）、外周血淋巴细胞（pbl）和6种散发性乳腺癌细胞系中BRCA1 mRNA的表达。正常乳腺细胞表达高水平的BRCA1 mRNA。散发性乳腺癌细胞系和pbl表达较低水平的BRCA1 mRNA，与正常乳腺细胞相比减少3-16倍。我们确定了BRCA1 CpG岛的600 bp区域具有很强的启动子活性（类似于对照组的40倍），并通过亚硫酸氢钠基因组测序确定了该区域内30个CpG位点的胞嘧啶甲基化模式。hmec、pbl和五种散发性乳腺癌细胞系大部分未甲基化。然而，一种散发性乳腺癌细胞系UACC3199在所有30个CpG位点上的甲基化程度大于或等于60%（18个位点100%甲基化），并且与正常乳腺细胞相比，BRCA1 mRNA减少了8倍。这些发现表明，BRCA1 CpG岛启动子的异常胞嘧啶甲基化可能是散发性乳腺癌中BRCA1抑制的机制之一。
BRCA1 mRNA is reduced in sporadic breast cancer cells despite the lack of mutations. Because a CpG island is found at the 5' end of the BRCA1 gene, we hypothesized that the decreased BRCA1 mRNA in sporadic breast cancer was associated with aberrant cytosine methylation of the CpG island. We examined BRCA1 mRNA expression in normal human mammary epithelial cells (HMECs), peripheral blood lymphocytes (PBLs) and six sporadic breast cancer cell lines using RT-PCR. The normal breast cells expressed high levels of BRCA1 mRNA. The sporadic breast cancer cell lines and PBLs expressed lower levels of BRCA1 mRNA ranging from a 3-16-fold decrease compared to the normal breast cells. We identified a 600 bp region of the BRCA1 CpG island that possessed strong promoter activity (similar to 40-fold above control), and determined the cytosine methylation patterns of the 30 CpG sites within this region by sodium bisulfite genomic sequencing. The HMECs, PBLs and five of the sporadic breast cancer cell lines were largely unmethylated. However, one sporadic breast cancer cell line, UACC3199, was greater than or equal to 60% methylated at all 30 CpG sites (18 sites were 100% methylated) and was associated with an eightfold decrease in BRCA1 mRNA compared to normal breast cells. These findings suggest that aberrant cytosine methylation of the BRCA1 CpG island promoter may be one mechanism of BRCA1 repression in sporadic breast cancer.