Promoter methylation correlates with reduced Smad4 expression in advanced prostate cancer
Promoter methylation correlates with reduced Smad4 expression in advanced prostate cancer
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DOI：
10.1002/pros.20730
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发表时间：
2008-05-01
期刊：
影响因子：
2.8
通讯作者：
Milis, Ian G.
中科院分区：
文献类型：
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作者：
Aitchison, Alan A.;Veerakumarasivam, Abhi;Milis, Ian G.
背景转化生长因子-β（TGF-β）是一种有效的生长抑制剂，在广泛的细胞类型。称为Mothers against decapentaplegic homologue 4（Smad 4）的TGF-β信号转导子是在染色体18q21.1上发现的已知肿瘤抑制因子，并且通常通过胰腺癌和结肠直肠癌中的缺失或突变而失活。目的探讨Smad 4基因在晚期前列腺癌中的表达、拷贝数及甲基化状态。我们采用甲基化特异性PCR（MSP）来确定Smad 4启动子内的甲基化位点，并将其与定量实时PCR相结合，以寻找甲基化状态和Smad 4表达之间的相关性，并检查雄激素受体（AR）的表达。细菌人工染色体-比较基因组杂交（BAC-CGH）已被用于寻找基因组扩增和缺失，这也可能有助于表达变化。我们没有发现影响18号染色体上Smad 4基因座的基因组缺失或扩增的证据，但在同一材料中显示了启动子甲基化和Smad 4表达丧失之间的相关性。我们证实，在30%的晚期临床样本中，X染色体上的AR基因座扩增，这与先前其他组报道的转录水平增加相关。这表明表观遗传变化影响了前列腺癌中Smad 4蛋白的表达，并指出启动子的甲基化是疾病预防的新标志物和贡献者，有待进一步研究。
BACKGROUND. Transforming growth factor-beta (TGF-beta) is a potent growth inhibitor in a wide range of cell types. A transducer of TGF-beta signaling known as Mothers against decapentaplegic homologue 4 (Smad4) is a known tumor suppressor found on chromosome 18q21.1 and is typically inactivated by deletion or mutation in pancreatic and colorectal cancers. The purpose of the article is to investigate Smad4 expression, gene copy number and methylation status in advanced cases of prostate cancer.METHODS. We have employed Methylation Specific PCR (MSP) to identify methylation sites within the Smad4 promoter and combined this with quantitative real-time PCR to look for correlates between methylation status and Smad4 expression and to examine androgen receptor (AR) expression. Bacterial artificial chromosome-comparative genomic hybridization (BAC-CGH) has been used to look for genomic amplifications and deletions which may also contribute to expression changes.RESULTS. We fail to find evidence of genomic deletions or amplifications affecting the Smad4 locus on chromosome 18 but show a correlation between promoter methylation and the loss of Smad4 expression in the same material. We confirm that the AR locus on the X chromosome is amplified in 30% of the advanced clinical samples and that this correlates with increased transcript levels as previously reported by other groups.CONCLUSION. This indicates that epigenetic changes affect the expression of the Smad4 protein in prostate cancer and points to methylation of the promoter as a novel marker of and contributor to the disease warranting further study.